%% Image and caption selected per Image Pickin' thread: http://tvtropes.org/pmwiki/posts.php?discussion=1330852481081235400
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[[quoteright:350:[[{{Franchise/Superman}} http://static.tvtropes.org/pmwiki/pub/images/supermath_4657.jpg]]]]
[[caption-width-right:350:In Super-math it may be [[MisplacedADecimalPoint 32,000]]. But in regular math, it's 3,200.[[note]]And that's ignoring the rounding errors.[[/note]]]]

->''Up in the sky, the alien mother ship sent down twenty hundred troops, three in each space jet.\\
And if you want to know how many jets there were, you can do the math yourself. I'm a very busy writer trying to make a movie here.''
-->-- ''Fanfic/CalvinAndHobbesIILostAtSea'' (a ScriptFic that imitates a movie)[[note]]Note that "twenty hundred" (2,000) is not divisible by 3 -- unless the number is accurate to three or fewer significant figures.[[/note]]
%% One quote is sufficient. Please place additional entries on the quotes tab. Thank you.

You're watching a show or movie, or reading a book, when suddenly something numerical throws you for a slight curve -- like a date, or a character's age. Your brow furrows. You start ticking things off on your fingers. What the hell? That wasn't right!

You have just discovered the fundamental truth: that your favorite author failed irredeemably at high school math and never wants to see a number ever again except in the corner of a page. This is a particular kind of continuity error that would be avoided if professional writers kept calculators at their desks. In their defense, some of these mistakes can be obscure and noticed only by die-hard fans. It can also come from multiple writers not checking with each other, or screwups in the timeline.

Compare SoapOperaRapidAgingSyndrome, NotAllowedToGrowUp, and LongestPregnancyEver, where the writers ''can'' do math -- they're just intentionally fudging it. See also SciFiWritersHaveNoSenseOfScale and NotDrawnToScale. Possibly the root cause of EverybodyHatesMathematics. Might even involve EEqualsMCHammer. ArtisticLicenseStatistics is a subtrope.

A natural habitat for the MST3KMantra and FanWank, as in many cases, these errors are not important for the plot ([[AnthropicPrinciple even when they are]]).

Oh, for the examples below that reference the number Pi, it is an irrational number with no limit -- an endless number -- of digits, but the first 12 are 3.14159265359.[[note]]Note that they're rounded -- the first 12 digits are 3.1415926535'''8''', and the next digit would be a 9, so the 8 is rounded up.[[/note]]


[[folder: Anime & Manga]]
* ''Anime/GhostInTheShellStandAloneComplex'':
** ''Major'' Motoko Kusanagi fought in World War IV in 2020. She must therefore have ended her five years of military training in 2010, and she must have been born at least 18 years earlier, in 1987 at the least. She was turned into a cyborg at age 5, thus in 1992... The writer probably just forgot to add all the cumulative time-periods together.
** Saito's [[WholeEpisodeFlashback flashback episode]] in the second season indicates that Motoko served overseas in an unofficial capacity; officially, the Japanese Self-Defence Forces avoided combat during WWIV, except for recapturing Nemuro. Ishikawa says that nobody knows who she is, only that she's "a genius at combat" and that everyone calls her "the Major". How she came by that rank is [[MysteriousPast somewhat up in the air]]. It should also be noted that this episode leaves it ambiguous whether this is something that actually happened or the whole thing was a story Saito made up to distract his poker buddies.
** Kusanagi didn't get her rank through normal process, but by getting hired by the Department of Defense as an irregular for her exceptional talent. It's heavily implied in the episode mentioned above that she is much more than she's letting on, only masquerading as a common soldier.
* Franchise/{{Dragon Ball}}:
** The eponymous objects can't be used for one year after they grant a wish, but only 8 months pass in between the first use in the series and the second one.
** If your family name is "Son", your age is going to get very confusing: \
Goku first claims to be 14, but nearly a year later claims that's because he thought 14 came after 11 so he's actually 12, yet according to the first point above, a year passed since he first gave his age, so he should be 13 (Then again... maybe his birthday is somewhere between May 7th and September 1st. It's not like Goku knows his birthdate anyway. Or he was wrong the first time too).\
Gohan's age at the start of the series is four. In the Buu saga, thirteen years later, his age is given as 16 when he should be chronologically 17, [[YearInsideHourOutside physically 18]].\\
Goten is 7 when we first see him, but just under 7 years went in-between the Cell saga and its TimeSkip to the Buu saga, so in order for him to be 7, he should have been ''born'' (not just conceived) during the Androids saga... where Chichi didn't even look pregnant. Figures.
** It is clear that Akira Toriyama has NO idea what a kilogram is. In Goku's second match against Tien he reveals that he has been fighting wearing 100kg of weighted clothing. Sure, that would be excessive in real life, but this shocks the guys who casually jump hundreds of feet into the air and shatter rock with their bare hands. Later on, the concept gets even more ridiculous; Goku, who in the beginning of the series is seen casually carrying a giant tree that must weigh a thousand tonnes, struggles to lift ten times his own body weight when he reaches King Kai's planet.
** In ''[[Anime/DragonBallZBattleOfGods Battle of Gods]]'', Bulma has her 38th birthday, even though she was 16 at the start of ''Dragon Ball'' and the movie it set 29 years later. While you could potentially construe this as her lying about her age out of vanity, [[spoiler:Mai of the Pilaf gang, who [[FountainOfYouth was turned into a child]] along with Pilaf and Shu and trying to blend in with the party, accidentally says her real age is 41--despite clearly being older than ''twelve'' when she's first introduced]].
* ''Manga/{{Naruto}}'' has numerous inconsistencies with character ages compared to state time periods, mostly because [[AllThereInTheManual these ages are only in the databooks]], so the author either doesn't remember them or [[SchrodingersCanon doesn't care about later contradicting them]]:
** A comment by Zetsu in Part II stated that Orochimaru left Akatsuki after trying to take Itachi's body 10 years ago, meaning Itachi was in Akatsuki two years ''before'' the Uchiha Massacre, and was '''11''' at the time.
** Supposedly Orochimaru conducted the Mokuton experiments on infants, or at least young children, but Yamato's age is given as 26 in the second part of the manga, and Orochimaru didn't know that he had survived because the experiments' discovery was what forced him to flee the village. This would mean that he left Konoha at least twenty years before the start of the manga. However, Anko is currently 24, but was somehow Orochimaru's student that far back (the databooks even say she was 10 when she graduated the academy). Likewise, Jugo is 18, but since he's what Orochimaru based the Cursed Seal he gave to Anko on before defecting Orochimaru would have ''also'' have to have met him before defecting. So either Yamato should be younger or Anko and Jugo should be older.
** When [[spoiler:Killer Bee is fighting Kisame]] there are some counting errors in the art: When he starts going into his [[SuperMode tailed beasts forms]], one form is shown with eight tails, but someone on the sidelines says there are seven and when he's reduced to one he says he lost six of them. When he takes another form we see seven tails in one panel, but eight in the next two. These were both corrected in the volume version: the first form had one of the tails erased and the second had a tail added.
** Konoha's ninja population seems iffy. During the 4th Shinobi World War, we are told that the Allied Forces comprise some 80,000 ninja and samurai. Konoha [[WordofGod supposedly]] has the largest population of any ninja village, but even if each village and the samurai contribute the same amount of soldiers, Konoha would still have to have at least 13,000 nin. Though we only ever see [[EconomyCast the same 50 Konoha ninja]], this is still possible. It's just that, according to Kabuto, there were 87 Konoha genin in the Chunin exam and, even accounting for genin who couldn't or didn't want to particpate, that seems like an incredibly small ratio. At the time of the chunin exams, the Rookie 9 are apparently the ''only'' new genin in Konoha. The exams are done twice a year, so that would mean that Konoha graduates ''at most'' 18 ninja a year. To put this in perspective, it would take 723 years to get 13,000 ninja this way.
** Konoha in its entirety has been shown in the manga and databooks, and it contains only a few hundred small buildings. So it would be unlikely that it accommodates a population of ten thousands Shinobi.
** Kakashi supposedly graduated from the Academy at age 5, and he became a chuunin by age 6. Obito and Rin both graduated at age 9 and became chuunins at 11. This means that for the three of them to be on same team during the time of Kakashi Gaiden, either both Obito and Rin should've been four years older than Kakashi, or Kakashi wasn't part of the same rookie gennin team as the other two, and joined them as a chuunin. However in a flashback to their first chuunin exam, they all look the same age, which is further supported by that Rin already had a crush on Kakashi, which would've been rather weird if he was six and she was ten, and they are on the same gennin team.
** The same chapter basically retconned the ages and graduation ages of every known adult to be in the same class. So apparently nobody graduated from Konoha for the next decade, or it's an incredibly coincidence that all known adults graduated around the same time.
** The students in Obito's class in ''Kakashi Gaiden'' are previously established characters, but of wildly different ages. Raido and Hayate, both shown in the class, were previously established as being 9 years apart.
** Iruka allegedly became the class clown after his parents died due to how lonely he was. Problem is, Iruka was 14 when they died and had graduated when he was 10, thus when his parents died he'd already been a genin for ''four years''.
** Supposedly a singly Ryo is worth roughly ten cents, however a single D-rank mission (which consists of chores like weeding, grocery shopping, and babysitting) costs a few thousand Ryo. So not only are people spending hundreds of dollars to have their fence painted, but there should be far less drive to reach higher ranks if a Genin can easily make a living wage just doing one or two D-ranks a day and never risk death on a mission.
* In an episode of ''Anime/DigimonSavers'', Marcus Damon has a flashback of one of his birthdays, in which he fell and tore open his head and his father ran him to the hospital. In the original Japanese, which birthday this was isn't stated, but in the dub, he had just turned six. How can this be possible if Marcus is 14, and his father has been missing for 10 years?
* In an episode of ''Anime/{{Doraemon}}'', Doraemon gives Nobita a special plate of cookies that double every 5 minutes (so if he starts with one, after 15 minutes he will have 8 cookies), warning him that he must eat every single one of them quickly. In the end, he throws away one and returns after a while to find a big pile of cookies. Unable to eat them all, they choose to throw them to space, and later Doraemon tells Nobita that a whole galaxy made of cookies has formed. In reality, if they doubled every five minutes, in less than 15 hours the mass of the cookies would be many orders of magnitude larger than that of the whole universe. [[ApocalypseHow Oops.]]
* In the original version of ''Anime/YuGiOh'', in Yugi's duel with Weevil Underwood at the start of the Duelist Kingdom arc, Yugi plays a card that raises Summoned Skull's attack power by 30%. 30% of 2500 is 750, but the attack counter goes up by 1000 points. [[TranslationCorrection This was corrected in the dub version]].
* In ''Anime/YuGiOhGX'', in the first duel against the Supreme King, there is one sequence where the King takes damage. Except that the damage he actually took is about 100 less than the damage he ''should'' have taken. This is {{egregious}} because had he taken that extra 100 damage, he would have wound up losing the duel. The same scoring error appears in Yugi's duel against mind-controlled Bandit Keith. Then again, since Keith is quite explicitly cheating, Yugi deserves a few extra lifepoints to give him a fighting chance.
* ''VisualNovel/SteinsGate'', [[ShownTheirWork of all things]], has a pretty serious error when it comes to Ruka's message. It is sent back in time seventeen years to Ruka's pregnant mother, in the hope of [[GenderBender changing her child's sex from male to female]]. However, it's been established that one second on the Phone Microwave ([[RunningGag name subject]] [[InsistentTerminology to change]])'s timer corresponds to one hour back in time, and seventeen years is about is 150,000 hours. The microwave's counter [[https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-prn2/t31.0-8/1412463_453647564746007_595751619_o.png only has five digits]], and presumably can't go over 99,999. Given the level of detail and accuracy in the rest of the series, it's entirely possible the staff noticed the former error and instead of trying to correct it, simply went "Fuck it" and left it that way.
* In ''Manga/{{Mitsudomoe}}'' the class is playing anything goes chairs at the start of the manga and anime. The rules are simple -- there are enough chairs in a circle to seat all but one member of the class. Whoever is left out has to call out a criterion, anyone who matches that criterion has to leave their chair and find a new one. After their initial rush for seats it appears that everyone in the class is seated. The teacher is confused at first thinking that there should be exactly one seat less than there are people -- it turns out the eldest daughter Mitsuba is sitting on a classmate who is on all fours. Catch is, if she is sitting on a classmate ''instead'' of chair then there are two people not in chairs and thus an empty chair somewhere which would have been obvious.
* In a ''Manga/BlackButler'' OVA, Thomas Wallis was born in 1775, and his scheduled death date was 1779. This would be fine if the boy didn't appear to be in his early 20s at the time of death.
* In a season two episode of ''Anime/MegaManNTWarrior'', Numberman is tied to a giant bowling pin by Bowlman, who starts knocking pins down. Numberman calculates the odds of his pin being hit as 10%, 20%, 30%, etc as the pins fall. Even if one assumes that Bowlman will only hit one pin with each ball, and that the odds of any given pin being his is identical (Which is most definitely not a sensible assumption when bowling), the odds of Numberman being hit would have been 1 in 10, followed by 1 in 9, 1 in 8, etc, or 10%, 11.1%, 12.5%, 14.3%, etc.
* The seven and a half year time skip in ''Manga/FairyTail'' manages to add ''exactly'' seven years... to the time when the story began. If you keep track of the dates it's actually been half a year since the story started, meaning an entire year just went missing somewhere.
* ''Manga/RaveMaster'':
** Haru claims to have been fighting for the sake of the world for two years, when every bit of evidence to come before and after that says he's been at it for one.
** Hiro Mashima freely confessed to miscounting the number of chapters he had left before he had to end the series. This meant that while several fights in the final arc involving the QuirkyMinibossSquad and more peripheral members of Haru's gang lasted a good long while, Haru's own fight with Lucia ended a chapter early, and another intended chapter where the two talked afterward was shortened to a single page.
* ''Manga/{{Bakuman}}'', or rather, ''[[ShowWithinAShow PCP]]''. "The only month this year in which the 9th is a Thursday is July." That's impossible: July 9th and April 9th are always the same day of the week.
* In chapter 156 of ''Manga/AssassinationClassroom'', it is stated that there are 26 days remaining until a March 13 deadline. That would make the date February 16 in a leap year, February 15 in a regular year. Two chapters ''later'', it's Valentines Day.
* Early in ''Anime/FullmetalAlchemistBrotherhood'' [[AnIcePerson Isaac Mcdougal]] says at one point that water is over 70% of his body. There is an in-universe formula for human body[[labelnote:ingredients]]35 liters of water, 20 kg of carbon, 4 liters of ammonia, 1,5kg of lime, 0,8 kg of phosphorus, 250g of salt, 100g of saltpeter 80g of sulphur, 7,5g of fluorium 5g of iron, 3g of silicon and trace ammounts of 15 other elements [[/labelnote]] and according to this formula water is about 60% of human body.

[[folder: Comic Books ]]
* Franchise/TheFlash saves a Korean city from a nuclear blast by carrying each citizen to a safe distance of 35 miles away at "a hair's breadth short of the speed of light" in .00001 of a microsecond (or 1/100 billionth of a regular second). Except if you do the math, getting that many people (stated to be one half million) so far away that fast would actually require him to have to be traveling ''[[http://i585.photobucket.com/albums/ss298/thatother1dude/TheFlashisreallyfuckingfast.png?t=1269402458 thirteen trillion]]'' times the speed of light. Going that far so many times at the speed of light, carrying "one at a time, sometimes two", would take between one-and-a-half and three minutes. The stated time period is so ridiculously short that even light travels less than '''3mm'''.
* Comicbook/JusticeSocietyOfAmerica member Stargirl is explicitly stated to be sixteen years old early in the book's run, and is still that old later on. Then, ''Comicbook/FiftyTwo'' and ''One Year Later'' happen as a TimeSkip thing. ''Then'' she celebrates her birthday. By all rights, she is now eighteen. It seems the policy of DC Comics is to no longer mention ages for any of their teenage characters. Comicbook/{{Supergirl}} also went through a recent birthday that, logically, would have been her 18th, but her age was not mentioned and she seems to be kept in the same "late teens" range as Stargirl and Comicbook/WonderGirl. Possibly subverted with Tim Drake (Comicbook/{{Robin|Series}}), since while his age hasn't been mentioned since his 16th birthday (pre-War Games), he seems to have aged into young adulthood and is traveling around the world without a guardian.
* The cumulative passage of time during the first arc of ''Comicbook/UltimateFantasticFour'' would make Reed Richards and Sue Storm 21 years old at the beginning their crime-fighting careers. Despite this, both heroes are explicitly stated to be no older than 18 in later issues.
* More a case of "Writers don't get units", but in an issue of the ''Second Coming'' crossover in ComicBook/XMen, the bad guys -- a loose coalition of anti-mutant paramilitants -- list off their armies, starting with "50 bases with a hundred men each" (so 5000 men, sizeable), "numbers in the thousands" (still large) and finally "40 armoured divisions." The latter would exceed 400,000 men, and thousands of tanks -- a completely ridiculous number for the organization in question. For comparison, the United Kingdom's entire armed forces currently consists of six divisions, ONE of which is an armored division, 40 armoured divisions would be larger than the ''entire Indian army'' and only slightly smaller than the Chinese one. 40 divisions would also be about twice the strength of the current U.S. Army.
* ''ComicBook/ElfQuest'''s timeline is by now properly beyond all help, because of too many authors RunningTheAsylum. Particularly Mantricker's timeline, the era between Goodtree's rule and Bearclaw becoming chief, makes ''no sense whatsoever'' anymore.
* Franchise/{{Superman}} demonstrates "Super Math" in [[http://s670.photobucket.com/user/calronmoonflower/media/supermath.jpg.html this comic panel]], but the writer is [[MisplacedADecimalPoint off by a factor of ten]]. Also, he's using nice and round numbers while ignoring the rounding error: with typical errors the figure of 3,200 could be off by up to 2,000.
* The ComicBook/{{Tintin}} book ''[[Recap/TintinDestinationMoon Destination Moon]]'' shows, at one point, a calendar page reading Thursday 13 May. The rocket launch takes place on Tuesday 3 June. These dates are exactly three weeks apart and therefore the same day of the week in any year.
* Marvel's CanonDiscontinuity miniseries ''Trouble'' purported to reveal that Aunt May was actually Peter Parker's biological mother. Problem is, writer Creator/MarkMillar presents Peter as the result of a teen pregnancy. Which would make May less than thirty-five when Peter gets his powers, instead of being in her sixties (616 Universe) or fifties (Ultimate Universe). Maybe baby Peter spent thirty years as a HumanPopsicle?
* In ''The Order'' by Creator/MattFraction, Ezekiel Stane claims a trap is 'surrounded by [[{{Unobtanium}} Vibranium]] walls twenty feet thick'. Given the size of the room, that would mean over two hundred thousand cubic feet of Vibranium; enough to make a full-sized Vibranium model of the Statue of Liberty. There just isn't that much Vibranium on the planet. It can be reasonably assumed that it's actually Vibranium-reinforced concrete, as with Avengers Tower.
* In the ComicBook/{{New 52}}, Bruce Wayne has only been Franchise/{{Batman}} for six years. That he managed to have four Robins in that time is unreasonable, but not impossible. However, he was already Batman when he fathered Damian...who is twelve years old. They later attempted an AuthorsSavingThrow by establishing that Batman has been active for much longer than six years, but was only considered an {{Urban Legend|s}} prior to that.
* Similarly, ComicBook/{{Nightwing}} has historically presented a massive issue for DC timelines, being one of the few characters with a hard timeline. Becoming Robin at [[ComicBook/AllStarBatmanAndRobinTheBoyWonder age 12]], then Nightwing in his late teens, and is depicted as being in his mid- to late-20s in current stories. This, in turn, locks other characters' ages as follows:
** Batman had to have been at least nine years older to take him as a ward, and probably a little older to get all that training and establish himself as Batman first, probably putting Bruce in his early 40s, past his physical prime.
*** This is averted, however, with GreenArrow prior to New52, who was established to be in his early 40s and being inspired by Batman in his youth.
** By extension, Jason Todd is also firmly established as younger than Dick, but taken in by Wayne sometime after Grayson became Nightwing. Jason is visibly drawn in his early days as about the same age as Grayson was at the start of his career as Robin, but only a few years younger than Dick now -- meaning Jason's aged around ten years in about half that time.
** All of the original TeenTitans are approximately Dick's age or younger. This only really presents a problem with Roy Harper/Speedy/Arsenal, Green Arrow's sidekick. Harper canonically is a single father of Lian Harper from an [[DatingCatwoman affair with villain, Chesire]], born before Harper became Arsenal, led the Titans, joined the Outsiders, joined the Justice League, etc. By the time of New52, it was clear that the affair would have to have happened while Roy was a minor.
* Once Creator/DonRosa created a timeline for certain events in the ComicBook/DisneyDucksComicUniverse to establish the ContinuityPorn used in his ''ComicBook/TheLifeAndTimesOfScroogeMcDuck'', several fans did the math and determined that Huey, Dewey, and Louie would have been born when their mother was 17, which has fueled plenty of fan theories about why she has had no contact with her family ever since her brother adopted the boys.
* In an issue of ''[[Comicbook/{{Stormwatch}} Stormwatch: Team Achilles]]'' cyborg baddie Ivana Baiul says her brain is located inside her torso, surrounded by "eight inches of solid diamondsteel". Accounting for the space in the middle taken up by her brain, this would mean a block of armor at least 20 inches (or half a meter) across. You couldn't fit that inside the chest of a world-class bodybuilder, and Baiul's cyborg body is the size of an average woman.
* In ''{{ComicBook/Asterix}}'', the battle of Alesia, historically in 52 BC, takes place several decades before the main timeframe of the stories, but each book reminds us that the year is 50 BC or around then.
** In ''Asterix and the Roman Agent'', Convolvulus tells the legionaries of Aquarium that they outnumber the Gauls twenty to one. As the garrison of Aquarium seems to be staffed by only a single century of legionaries (they're headed by a ''centurion'', after all), and as a century was 80 legionaries, this puts the size of the Gaulish village at ''four people''. Even if Convolvulus meant the all four garrisons surrounding the village for a total of 240 legionaries, this still means there are only 12 Gauls in the whole village. If anything, based on group drawings of the village, the Gauls outnumber the Romans. It's even worse in ''Asterix and the Big Fight'', where Asterix declares the ratio of Romans to Gauls to be ''one hundred'' to one.

[[folder:Fan Fiction]]
* In ''Fanfic/LightAndDarkTheAdventuresOfDarkYagami'', a "sevensome" goes on between ''six people'': Sayu, Misa, Dark, [[BrotherSisterIncest Light]], [[ParentalIncest Light's mom]] and the girl from the bus.
* Exploited in ''Fanfic/GeorgeWeasleyAndTheComputationalError''. Because Creator/JKRowling is lacking in math skills and the universe knows it, it ignores those errors as a matter of course. Thus, it assumes that an extra duplicate (such as a long-range time traveler) of someone with a previously known duplicate (such as someone with an identical twin) running around is a [[TitleDrop computational error]] and not something to worry about.
* One of the few mess-ups in ''Fanfic/DeadGarden'' occurs when Mizuki is revealed to have been a former genin teammate of Sakura's father Takeru and well acquainted with her mother Amaya. In-canon, Mizuki is a colleague of Iruka and could be no more than a few years older than him at most. When Sakura was born (and her mother died), Iruka (and by extension Mizuki) was still a kid in the Academy. Since genin teams are made up of kids from the same graduating class, or at least roughly the same age, the two facts do not add up.
* This is the case in the ''FanFic/Gensokyo20XX'' series in that Amoridere isn't very good at math (she's noted this herself), explaining why it mostly measures by months, rather than years (i.e. "A few months passed), never at all giving the exact numbers, and mostly going on ComicBookTime. This can be seen with ages of the children, which is rather complicated, as Reimu's age-regression age is currently either seven or eight and she was supposed to be three if not four during the events of Gensokyo 20XXIII and 20XXIV, and it was noted that two years have passed between 20XXIV and 20XXV and Reimu's age-regression age then was supposed to be either five or six, which would probably make Yume Ni four and An three, leading one to question exactly how many years have passed in Gensokyo 20XXIV. On the note of Yume Ni, this is especially hard to figure out in that what is known is that Yume Ni was born some time before the nuclear war and the resulting winter, whereas An was born some time during the nuclear winter. This is referenced in-universe where Ren stated Yume Ni and An were two and three, when they are likely to be older than that and Reimu's age-regression age is stated to be either seven or eight, never exactly which. Thus, the exact estimate we get to that is that they're ages are vague. This is averted in one chapter of 20XXV, where the correct answer to 6x20 is stated to be 120.
* In Webcomic/KillLaKillAU, this is averted in the kids ages are correct, in that Satsuki is eleven, making her two years older than Nui, who is nine, which in turn makes a year older than Ryuuko, who is stated to be eight. However, one would have to wonder how old their parents are, seeing that Ragyo's mother's hair is grey when we first see her.
* ''Franchise/AceAttorney'' fanfic ''[[https://www.fanfiction.net/s/7269974/1/Her-Life-or-Mine Her Life or Mine]]'' gets about every canon date or relative age wrong.
** Fanfic takes place between Hazakura case [[labelnote: Note]]last case of third game[[/labelnote]] and [[spoiler: Phoenix's disbarment]][[labelnote: Note]]Which takes place in backstory of fourth game[[/labelnote]] and supposely starts in 2005. DL-6 incident canonically took place in 2001 and first game takes place ''fifteen'' years later.
** Events of the fic take place over 15 months. Considering that Phoenix is the same age during Hazakura case and when [[spoiler: he was disbarred]][[labelnote: Note]] he's 26 in Hazakura, and while his age during disbarrment isn't stated he's 33 during main story of ''Apollo Justice'' which takes place 7 years later. Do the math.[[/labelnote]] there is no way to squeze in over a year between them.
** [[OriginalCharacter James]] mentiones that Maya is a year older than him and he was fifteen during the events of the first game. During the first game Maya was 17.
** He also claims that Pearl was 8 during said events. Pearl was 8 during her first appearance in ''second'' game which canonically takes place a year after the first one.
** He says that Dahlia is about 7 years older than him. ''One sentence later'' he says that when they met first time he was 11 while Dahlia was 15.
* In ''Fanfic/CellarSecrets'' we have this initially the case with Satsuki, when the story stated that she was 21, when actually she was 20. This came from the authoress miscalculating 17.5 + 2.5 and thought it added up to 21, when it actually added up to 20, going back to change it.
* Another ''Franchise/AceAttorney'' fic ''[[https://www.fanfiction.net/s/9106855/11/The-Fated-Turnabout The Fated Turnabout]]'' takes place in 2018, and Lyn goes on a date with [[spoiler: Larry]] on sunday, April 18th. That date in 2018 was a wednesday.

* In ''Film/HomeAlone'', Kevin is 8 years old; in ''Home Alone 2'', Kevin is 10, the same age as actor Macaulay Culkin who plays him was at time of filming; that is, the sequel was made two years after the original. But it was ''set'' '''exactly''' one year later. Either his birthday occurs over the course of both movies (and nobody bothers to mention it), or he should be 9.
* ''The Heavenly Kid'' has the title character die in what is clearly the late '50s or early '60s. He's then brought up to ThePresentDay (1985) and discovers he sired a son, who's now in HighSchool. Apparently, his son had to repeat a few years.
* ''Film/ItsAWonderfulLife'':
** Clarence says that, in the altered reality, Harry Bailey died at the age of nine, but the gravestone ''right in front of him as he says the line'' reads "1911 - 1919", making him either 7 or 8.
** Clarence implies that he was a contemporary of Mark Twain, then later calculates his age as 293 ("next May"). That would have put his birth in 1653: many, ''many'' years before Mark Twain.
* ''Film/{{Pi}}'':
** Mathematician/genius Max Cohen tells the Kabbalists that he can't just tell them the 216 digit MacGuffin number because "You've already written down every 216 digit number and intoned them all and what has it gotten you?" To do so would, of course, take even a large group of researchers, such as the entire population of the Earth, significantly longer than the age of the Universe to do, and inconceivably more ink than there is mass in the universe -- indeed, even if only one electron were needed to write down each number, 10^100 universes would be ''much'' too small. Any mathematician should be well aware of this. Of course, [[MindScrew Max and reality don't always see eye to eye, especially considering he's having a schizophrenic breakdown at that point]].
** Also, the Kabbalists are after it because they're looking for a 216 character word. Since this would be in Hebrew, which has 22 characters, they actually want a number with roughly 290 digits. So Max probably doesn't even have what they want.
** Max also describes the golden ratio by writing a:b::a:a+b. He means a:b::'''b''':a+b; the version he wrote immediately gives b=a+b, so a=0. (Interestingly, this error isn't in [[http://www.imsdb.com/scripts/Pi.html the script]].)
* Played with in ''Film/StrangerThanFiction'': Harold is asked a complicated math question and can't think because of the narrator in his head. She tells him an answer, which he promptly says out loud. She then says that answer was wrong and gives another one, causing Harold to apologize and switch to the new answer. The first answer was the right one. This was intentional on the part of the writer.
* ''Film/TheWizardOfOz'': The infamous "Sum of the square roots of any two sides of an isosceles triangle is equal to the square root of the remaining side." mangling of the Pythagorean theorem, as said by the scarecrow after he got his brain. It should be, "The square of the hypotenuse of a ''right'' triangle is equal to the sum of the squares of the other two sides." (Of course, since the Scarecrow hasn't actually had any real increase in intelligence or learning, this could be intentional; he thinks he's now clever, so he says something that ''sounds'' clever). This is lampshaded in ''WesternAnimation/TheSimpsons'', where Homer says the exact same line in an attempt to sound smart after putting on Henry Kissinger's lost glasses, and a person in the bathroom yells out, "That's a right triangle, you idiot!" Homer then responds to this with [[CatchPhrase "D'OH!"]]. The French dub of the film (titled Le Magicien d'Oz) averts the mistake, where the Scarecrow says "La somme de l'hypoténuse au carré doit être égale á la somme des deux cotés opposés au carré", or "The square of the hypotenuse must equal the squares of the two other sides" in English.
* ''Film/TransformersRevengeOfTheFallen'': 5 Decepticons go into the water to revive Megatron. When they get down there, they kill one for parts and revive Megatron. When they go up, a sub commander says that six are going up.
* In ''Film/ForrestGump'', Forrest claims that Jenny died on a Saturday, and yet her gravestone says 22 March 1982, which was a Monday. Odd that Creator/RobertZemeckis would make that mistake, considering he so thoroughly avoided it in the ''Film/BackToTheFuture'' films.
* One scene in ''Film/StTrinians'' had ''Stephen Fry'' award points to a team for concluding that the volume of a sphere is πr^3. A fourteen-year-old could probably tell you that it's actually (4πr^3)/3. Clearly the writer extrapolated from πr^2 giving the area of a circle. Although he claimed in his biography to enjoy studying maths under his father, Stephen Fry is much better versed in humanities than mathematics, otherwise he might have spotted this one.
* In ''Film/NeverBeenKissed'', the geeky kids sell pies at a bake sale, with a sign proclaiming "pi = 3.1457" followed by some more digits to make it look sufficiently nerdy. Only the first three digits are correct; the rest is nonsense. Also, Josie's initial high school tenure is played against the backdrop of TheEighties, when, based on the dates and ages mentioned, they actually should have occurred in 1992, 1991 at the earliest. Instead of the soundtrack you'd expect to hear for a sequence set during the heyday of {{Grunge}}, Josie and her classmates are always shown cavorting around to Cyndi Lauper and Music/TheSmiths, music more apropos of what should have been their grade school years.
* ''Franchise/{{Terminator}}'':
** The Judgment Day was to occur August 1997. John Connor was born February 1985. ''Film/Terminator2JudgmentDay'' shows him at the age of ten being attacked by the Terminator. ''Film/Terminator3RiseOfTheMachines'' then {{Retcon}}s his ''T2'' age to thirteen. The problem is that he wouldn't turn thirteen for six months after the bombs supposedly fell in Kyle Reese's timeline.
** In the second movie (set in 1995), Dr. Silberman explicitly refers to Sarah as 29 years old. In ''T3'', the gravesite indicates that she was born in 1959, which would have made her 36 in that year, and 24 or 25 in the first movie, where she is stated to be eighteen.
** Kyle Reese questions a policeman at the beginning of the first film about the date, and gets the response "12th! May! Thursday!" However, that date in 1984 was a Saturday. It would have been the correct weekday in 1983, which was when the film was originally supposed to be made, but it was postponed due to Arnold Schwarzenegger having other commitments.
* Alex O'Connell's age in ''Film/TheMummyReturns''. He's eight in 1933, so he'd have to have been born in 1925. Rick and Evy met in 1926. Neat trick, Alex. The writers for ''Returns'' appear to have missed the fact that the first film has a time skip of a couple years between O'Connell's first appearance and him meeting Evey.
* In ''Film/{{Roxanne}}'', a modern-day remake of ''Theatre/CyranoDeBergerac'', C. D. Bales agrees to make twenty jokes about his own nose, in what qualifies as a Crowning Moment of both [[CrowningMomentOfAwesome Awesome]] and [[CrowningMomentOfFunny Funny]]. Apparently he and the rest of the bar patrons lost track. He actually did twenty-five jokes. (WordOfGod says the bar knew and just wanted C.B. to do more insults.)
* In the ''Film/JamesBond'' movie ''Film/{{Goldeneye}}'', the BigBad seeks revenge against the British government for betraying his parents at the end of World War II (leading to their deaths), then figuring he would be too young to remember. Seeing as how he's roughly the same age as Bond (somewhere from mid-30s to early 40s), he's too young to ''exist'' before then.
** This was averted in the 2010 [[VideoGame/GoldenEyeWii Wii remake]] of [[VideoGame/GoldenEye1997 the original game of the movie]]: since the game is set in the present day, said BigBad's motivation is changed to [[spoiler:outrage over the 2008 Financial Crisis and the complicity between his former employers and the bankers that caused it]].
** This is a misconception; the villain's parents survived Stalin's executions and his father killed his mother in a murder-suicide out of survivors guilt; however, it is never stated ''when'' the father did this or the guilt was too much for him, and could have been years or even decades later, by which time the BigBad could indeed have been born.
** It should be noted that the character was originally written as a mentor figure to Bond, with Creator/AlanRickman and Creator/AnthonyHopkins both considered, who would have both been the right age.
* In ''Film/MeanGirls'' Cady is supposed to be a mathematical genius, so the writers used really overcomplicated explanations of how to do simple things like working out percentages, but seem to be okay in terms of accuracy. However, Cady [[ObfuscatingStupidity intentionally]] makes mistakes to help her crush/tutor feel smart, leading to moments like this little exchange:
--> '''Aaron''': ...sometimes the product of two negative integers is a positive number.
--> '''Cady''': Yeah, like negative four and negative six.
* In ''Film/NightAtTheMuseumBattleOfTheSmithsonian'', an Einstein bobblehead (supposedly as smart as the real Einstein) claims that pi is ''exactly'' 3.14159265. Pi is an irrational number, meaning that no matter how many digits you use, you can never get to the exact value.
* ''Film/KellysHeroes'', a UsefulNotes/WorldWarII film, features a [[TheCaper bank heist]] of 14,000 bars of NaziGold supposedly worth $16 million in 1944 dollars. No matter how you do the math, these figures cannot be reconciled with (a) the number of shares, (b) the observed weight and size of the bars, (c) the number of boxes. See the Headscratchers.KellysHeroes page for all the gory details.
* ''Film/MammaMia'' has a real doozy; it is set in the modern era, as the clothing of the main characters and a line about a "web site" would indicate. At the ''earliest'' it would have to be set in about 1998, when advertising your business via the Internet became a thing. The film revolves around a 20-year-old girl trying to find out which of three men is her birth father, meaning she would have been conceived, again, ''at the earliest'', in 1978 (but probably as much as a decade later, as nothing indicates the film isn't set in the same time period as when it was released, in 2008). However, many lines of dialogue, and one song, indicates that her mother met these three men during the early to mid-sixties (Creator/PierceBrosnan's character dressed like a hippie when younger, plus Stellan Skarsgaard's character out-and-out states that "those crazy years, that was the time of the flower power"). This is also consistent with the fact that Meryl Streep, Christine Baranski and Julie Walters play "childhood friends" who were apparently also a short-lived singing group ''in the sixties'' meaning that they would have had to be at least in their late teens by then, and all three of them (and all three of the potential fathers) appear to be somewhere in their mid- to late-fifties. Not just appear; they refer to each other getting "old", and at one point Baranski refers to Walters as a "senior citizen". Okay, so maybe Streep's character was impregnated later in life. Nope; repeated dialogue has her in her late teens when she got pregnant. So, to recap: Streep, as a young girl in her late teens in the early to mid-sixties, was in a singing group at the time, and met three men, one of whom impregnated her...with a daughter who is still twenty years old in either the late 90s, or (more likely) somewhere around 2008!
* In ''Film/XMenFirstClass'' there is a scene with Charles Xavier as a child which is set in 1944, while the bulk of the story takes place in 1962. However, the two actors are credited as playing "Charles Xavier: 12 years" and "Charles Xavier: 24 years."
* The prologue of the original ''Film/{{Halloween|1978}}'' takes place in 1963 and Michael is explicitly six years old. The rest of the film takes place in 1978, and yet the credits list Tony Moran as playing "Michael Myers (age 23)." He should, of course, be 21.
* ''Film/{{Entrapment}}'': Catherine Zeta-Jones needs ten extra seconds after midnight in order to use a computer program to steal billions of dollars from an international bank. After 11pm, a device she set up "steals" 1/10th of a second every minute until midnight, which will total 10 seconds by midnight. But that only equals 6 seconds, which is 4 shy of the required 10.
* ''The Odd Couple II'' is an absolute mess of chronology. The script is never sure how long this film takes place after the original: 30 years (which was the real-time length between the films) or 17 years (because the plot revolves around the marriage of Felix and Oscar's children, neither of whom look much older than 30). The opening caption states "30 years later", but dialogue throughout the next few scenes keep insisting it to be 17 years. And then near the end, Felix and Oscar are confronted with their ex-wives, both of whom they separated from during the events of the first film. Oscar's ex tells him he hasn't changed in 30 years, and then Felix tops it by declaring that he hasn't spoken to his ex in 50 years (!), which would be impossible without their daughter being well into middle-age. What happened, Neil Simon?
* In ''The Man in the Moon'', a boy is taking the oldest daughter to a school dance. The dance ends at 11:00, so Dad demands that his daughter be home by 11:30. The problem is that the school is near 30 miles away. That would require going almost 60 mph on back roads. Dad does interrupt the boy's answer with a possible ConjunctionInterruption; we don't know what the boy was going to say, but it could have been to note that fact.
* Judge Dredd gives the crime rate in Mega-City One in ''{{Film/Dredd}}'' as "Twelve serious crimes reported every minute. Seventeen thousand per day." This is obviously meant to sound astonishingly high to the audience, but at the same time the city has a population of over ''800 million''. Doing the math, that means about 780 "serious crimes" per 100 000 residents per year (which is a standard method of expressing crime rates). In comparison, the violent crime in New York city was considered high in the 1980s, that number hovered around 900-1100, while 2010 had a "historical low" of 581. Of course, we do not know what exactly is considered a "serious crime" in Mega-City One or the number of crimes that just go unreported, which seems rather high based on the comics.
* In ''Film/SuperMarioBros'', Spike, after being turned super-intelligent, asks Iggy what the square root of 26,481 is, while delivering the answer immediately: 191. The thing is, 191 is actually the square root of 36,481.
* At the end of ''Film/SummerSchool'', the students' final grades in Remedial English are recounted in front of their teacher and two school administrators. Apparently the ''vice-principal'' could use some Remedial Math, because the average he cites for the class as a whole (63%) isn't the actual mean of the grades reported (43, 51, 74, 38, 75, 59, 70, 82, 91).
* In ''Film/RushHour'', the kidnappers demand fifty million dollars in ransom: 20 million in fifties, 20 million in twenties, and 10 million in tens. That adds up to ''two million, four hundred thousand'' separate bills, and yet all that money apparently fits in two ordinary briefcases, which the villain attempts to escape with in the end. Those briefcases would weigh over ''five thousand pounds''.
* ''Film/PhoenixWrightAceAttorney'': In the present day, Prosecutor Mandred von Karma hasn't lost a case in 40 years. Phoenix says that Gregory Edgeworth found it suspicious that he hadn't lost a case in 40 years... but Gregory was killed 15 years ago, which means von Karma's streak was 25 years at the time.
* ''Film/ASeriousMan'': When Larry scrawls the equations of [[https://en.wikipedia.org/wiki/Uncertainty_principle the uncertainty principle]] on a chalkboard, he miswrites one of the equations as "Δp = √(<p>^2 - <p>^2)", making the equation [[DivideByZero equal the square root of zero]]. The correct equation is "Δp = √(<p^2> - <p>^2)".

[[folder:Film - Animated]]
* A definite example exists in ''Disney/BeautyAndTheBeast'' at the beginning of the film, the enchanted rose is explicitly stated to bloom until he was twenty one years of age. It has already started to wilt and lose its petals because this is the final year. The song "Be our Guest" has Lumiere state that they've been cursed for ten. It's very clear that the prince is running out of time to break the spell, but it also means that he was eleven years old at the time he was transformed into the Beast. True to the trope, he looks and acts far older in ''Disney/BeautyAndTheBeastTheEnchantedChristmas'' which depicts the night he was transformed. He certainly doesn't sound eleven and he hardly looks prepubescent.

* An OlderThanPrint example: In the ''Literature/{{Nibelungenlied}}'', Siegfried and Kriemhild have a son who is born in the tenth year of their marriage. Shortly after that Siegfried is murdered by Hagen. Kriemhild then spends three and a half years mourning for him before accepting Etzel's proposal. Twelve years into her second marriage she invites her brothers for her party of revenge. So the second half of the epic takes part more than 25 years after the first part (from Siegfried's arrival at Worms to his and Kriemhild's wedding), but characters don't age accordingly. Giselher, the youngest of the brothers is still referred to as "the child", while Siegfried's son [[WhatHappenedToTheMouse disappears from the narrative without explanation after Siegfried's death]] [[NotAllowedToGrowUp even though he should be about sixteen, grown up by medieval standards, by the end]]. Hagen's feat of single-handedly sinking Siegfried's gigantic hoard (more than 1000 wagonloads) in the Rhine is, shall we say, highly improbable, as was his later feat of ferrying the Burgundian train (10,000 men) across the Danube in one day with just one boat.
* An OlderThanPrint aversion in ''Literature/TheCanterburyTales'' in which the Host (correctly) guesses the height of the sun based on the height of a tree and the length of its shadow.
* In ''Literature/ArtemisFowl'' the titular character's bodyguard, [[BattleButler Butler]] stands at almost seven feet tall, has "a barrel chest full of scars and hard muscle", hands that are "the size and approximate shape of spades", and is frequently referred to as a "man mountain" by other characters. However, in ''The Eternity Code'' he's described as a "ninety kilo [200 lb] dead weight." A near-seven foot tall man at that weight would be as thin as a rake, while a man of Butler's proportions would weight ''at least'' 350 lbs [~160 kilos].
* In ''Literature/RainbowSix'', we are told a group of terrorist is composed of 15 people. However, there's three trucks with three terrorists in each (9), five in the hospital (14), the boss (15), and his second (16). Furthermore, we are told only six of the fifteen (well, sixteen) survived, which is not true: four of the hospital group surrendered, the boss was captured alive, as was one of the truck drivers. Furthermore, an entire truck was flashbanged, and all three of its occupants were captured, which would make for nine prisoners, not six.
* The ''Literature/HarryPotter'' series has many examples, generally called "oh dear, maths" moments after the World Book Day interview, where Creator/JKRowling admitted she's not good at mathematics (though her [[Literature/CormoranStrikeNovels detective novels]] are better about it):
** In ''Literature/QuidditchThroughTheAges'', it says that the first ever World Cup was in 1473, with a match being held every four years. Yet the World Cup in ''Goblet of Fire'', set in 1994, is number 422. There can't be 422 world cups in 521 years with a four-year gap in between[[note]]There are tourneys [[http://en.wikipedia.org/wiki/Copa_América#Results which had erratic patterns before getting into regular intervals]], but that's a detail[[/note]]. Calculated correctly, the World Cup that the Weasleys, Hermione, and Harry attend is actually the 131st, and it would have been held in 1993.
** Then you have Tonks and Teddy. There is time for the pregnancy, but it's really squeezed in there. Tonks was either pregnant when she got married(which is not unlikely, given that she and Remus were apparently together -- and presumably intimate for at least part of the time -- from before the beginning of ''Half-Blood Prince''), or very soon after, and behaves as though she's aware of the pregnancy as soon as it would have started.
** Dudley has a UsefulNotes/PlayStation in the fourth book, which would have taken place in 1994, before the [=PlayStation=] was even released in Japan, let alone Europe. Rowling admitted she got it wrong with that one.
** The most commonly noted example: It's implied (but never explicitly stated) that students are divided more or less evenly into houses. There are 5 Gryffindor boys in Harry's year, as well as 5 named Slytherin boys. That suggests there are roughly 40 students in Harry's year -- and J.K. Rowling even [[WordOfGod has a notebook listing them]]. If we assume this is a normal year... we are led to the conclusion that there are no more than 280 students attending Hogwarts. J.K. Rowling has stated that she had just been so proud to have 40 rounded-out characters that she didn't do the math. She envisions Hogwarts to have somewhere around 750 students; and there is a line about "200 students in green" during one of the Quidditch matches, supporting the view of a larger student body. It's even more egregious when you take into account that Houses are usually separated for most classes; the films even had to combat this by showing all Houses having classes together so as not to show a class full of just ten people.
** Another problem with the "large Hogwarts" view: there are fourteen subjects, just one teacher for each (so says WordOfGod, with the exception of Divination after the events of the fifth book) and on several occasions it's mentioned that there are 20 students in each lesson. If there were 750 students, either the day would be two-thirds free periods or the teachers would all have to be using Time Turners to teach three classes at once.
** The matter of Ron's older brothers, Bill and Charlie: originally, Rowling stated that Charlie was two years older than Percy, and Bill was two years older than Charlie. However, Percy is in fifth year in ''Philosopher's Stone'', meaning that Charlie should have either been in seventh year, or just graduated. She later corrected this to Charlie being three years older than Percy -- which is still impossible, as the Gryffindor Quidditch team has allegedly not won the Cup since Charlie stopped playing for them, and the period of time since Gryffindor has won is given in "Prisoner of Azkaban" as having been seven years, coming up on eight (or four years before the start of the first book). Charlie would have had to have left the team in his third, or possibly fourth, year for his age at three years older than Percy to be plausible -- unlikely, since he was Quidditch Captain and "could have played for England". Bill was born in 1970 and would have finished in 1987 (four years before PS, not 8), Charlie was born in 1972 and would have finished in 1989 (2 years before PS not 8), Percy in 1976, Fred and George in 1978, Ron in March 1980 and Ginny in August 1981.
** In ''Chamber of Secrets'', Ginny mentions wanting to attend Hogwarts ''since Bill came''. Bill went to Hogwarts a year after Ginny was born (and that's without the earlier dates from the paragraph above). So Ginny wanted to go to Hogwarts ''since she was one''? Or ''before she was born''? It was also unnecessary because she has 4 older brothers she would've been able to bond with before they went off to Hogwarts. (Of course, she wasn't exactly thinking clearly at the moment.)
** Then, of course, there is the number of wizards and witches in Great Britain, which Rowling puts at around 3,000. That's all fine and good until you start wondering how they support ''multiple'' professional, regional Quidditch teams, among other things, with a population that small. And that about a third of the population is apparently at Hogwarts for most of any given year. There also seems to be a rather oversized governing and law enforcement body for such a small community. Towns with many more than 3000 inhabitants generally merit a small town council and a single police station (and often not even that these days), not a large government with an expansive bureaucracy and extensive law enforcement with special forces and intelligence sections. It seems the entire wizard population must either be government, Quidditch players, or in school.
** In the ''Philosopher's Stone'', we are told the Nicholas Flamel is 665 years old. The book is actually set in 1991-92, making Flamel's birth 1326/1327. However, Flamel was a real historical figure born in 1330.
** The Black Family Tree has plenty of errors:
*** Sirius Black mentioned once that Bellatrix Lestrange was in the same social group as Severus Snape at Hogwarts. However JK Rowling has said that Snape was born in 1960 and according to the Black Family Tree that she drew, Bellatrix was born in 1951. This means that she must've left two or three years before Snape was even a first year.
*** Even ignoring the family tree dates, Bellatrix is the oldest of three sisters. Her younger sister Andromeda was Tonks's mother. Tonks was in her early-mid 20s throughout the series making Andromeda a very young mother. If we assume Andromeda didn't have her child until she graduated Hogwarts and that Bellatrix was at least a year older than her, Bellatrix would still have to have been a sixth or seventh year when Snape was a first year, which would be strange if they were part of the same social group.
*** Another mistake is that the Black sister's father would've been about 13 when he had Bellatrix and 17 when he had Narcissa. Walburga's father also would've been 13 when he had her.
** Presumably Harry's paternal grandparents (i.e. James' parents) are dead by the time he's orphaned. Seeing as James was 21 when he died, his parents were probably no older than 50 or 60. So either they were killed by Voldemort, which you'd think would get mentioned at some point; or they ''both'' died of some kind of accident or illness before age 60, which seems unlikely; or JKR envisioned that they died of natural causes despite wizards' natural lifespans appearing to be upwards of 100 years, and just didn't do the math.
** Actually, James Potter's parents have been stated to have been old 'even for wizards' when they had their only child, meaning that they both died of old age before James and Lily's death. This assumes that witches either don't have menopause like muggle women, or go into menopause much later (James's mother being around eighty when she gave birth) and with a much shorter period between infertility and end of life expectancy BUT there's nothing to suggest it isn't true or possible. This was probably one of Rowlings many afterthoughts, but at least it explains how Harry has no living wizarding family (any of James's uncles and aunts could also be dead of old age before his death) and how he's absolutely loaded.
** Chalk this up to calendar fail. Every September 1, the students arrive at Hogwarts and the classes start the next day. However, in ''Order of the Phoenix'', September 1 was on a Friday and classes started the next day. So either they started classes on Saturday or Rowling just didn't think of this.
** In addition, although this may just be because of the [[CommonKnowledge general misconception]] that the Matter of Britain took place during medieval times, Merlin is described as going to Hogwarts. Merlin was alive in the sixth century, and according to the fluff Hogwarts was founded in the tenth, so in order to go to Hogwarts Merlin would need to have gotten education 300 years after he supposedly assisted Arthur. Of course, if there's one fictional character who can justify using knowledge before he learned it it's [[MerlinSickness Merlin]].
** The Slytherin Quidditch captain Marcus Flint is still at Hogwarts in Harry's fourth year when he should have graduated the year before. JK Rowling herself said "either I made a mistake or he was held back a year. I think I prefer Flint making the mistake."
** ''The Cursed Child'' reveals that [[spoiler: Bellatrix and Voldemort have a daughter. As Bellatrix was freed from Azkaban only midway through the fifth book and is still actively fighting with the Death Eaters for most of the seventh, it gives a very narrow window for her to have conceived. It had to have been at some point in the sixth book where there's less of her]].
** For someone who apparently has dyscalculia, Rowling talks percentages a lot. She said she "made up 95% of the magic" in the books, by which she probably means the pseudo-Latin formulas and their effects. She also claimed that Snape was "about 80-85%" her old chemistry teacher, and ten or so percent a sadistic teacher she had in primary school, and the rest a third, unnamed person who is theorized to be herself.
* ''Literature/TheBabySittersClub'': The number of bedrooms in Watson's house never seems to add up. Kristy says his house has 9 bedrooms, which should mean one each for Watson and Elizabeth, Kristy, Sam, Charlie, David Michael, Karen, Andrew, Emily Michelle and Nannie. However, in another book Kristy says that each of her brothers could have a whole suite of rooms if they wanted, and occasionally they've had entire families stay over with no discussion of people moving or sharing rooms. However, possibly the "9 bedrooms" refers only to the bedrooms on the first and second floors. It's mentioned that there is a third floor and an attic that are never used (which is most certainly not because the ghost of Ben Brewer haunts them), so her brothers could ''have'' suites, but would have to move to the upper floors.
* ''Literature/TheGiver'' has ridiculously strict population control methods doomed to fail. Even with a completely cooperative populace, it will still fail because of math.
** Each family unit is allowed a maximum of 2 children, the same number of children are born each year and they are all assigned to a family unit. Not all adults have children, and not all family units have the maximum of 2 children.
** Birth mothers, the only job that allows giving birth, are only allowed to have 3 children each before they become laborers. This would require that at least 2/3 of all women become birth mothers to maintain a stable population, but this doesn't happen at the beginning of the book as the administration is handing out jobs to graduates.
* The people of ''Literature/{{Wool}}'' have population control laws such that only lottery winners can have a single child. Only lottery winners who naturally conceive twins can have two children. Somehow, the population keeps growing.
* There's a children's book titled ''Brog the Stoop'' in which the race of Stoops are restricted to '''one''' child per family. The author really should have noticed that this would lead them to die out very quickly, each generation being at most half the size of the previous one.
* A plot point in ''The Power of Un'', where the TimeTravel MacGuffin has to accept its figures as the number of minutes to be rewound -- so, of course, the hero gets his math wrong and accidentally goes back to the beginning of the previous day. However, the author gets his math wrong ''twice''; first of all, the time he ends up at is not consistent with his answer, and, when Rainy is asked to provide the correct answer (much to her bemusement, since to her, it's just a random, spur-of-the-moment multiplication problem), she gets a result which is ''still'' incorrect.
* In ''Literature/TheLegendOfRahAndTheMuggles'', Stubby aged from five to fifteen over the course of twenty-two years.
* Timeline difficulties are very common in Literature/{{Tortall|Universe}}. Some fans have spent [[http://www.geocities.com/f4_soujiro/timeline.html a lot of effort]] trying to make sense of it all. This is because Creator/TamoraPierce actually has dyscalcula, which is like dyslexia with numbers.
* Rick Cook's fantasy novel ''[[Literature/WizBiz The Wizardry Compiled]]'' contains this fantastic explanation of the concept of "fencepost error" by a supposedly guru-level programmer:
-->'''Master''': Yeah. Look, say you've got a hundred feet of fence to put up and you need to put a post every ten feet. How many posts do you need?
-->'''Pupil''': Ten, of course.
-->'''Master''': Nope. Eleven. Unless you string your fence in a circle. If you put the posts in a closed figure, you only need ''nine'' because you start and end on the same post.
-->'''Pupil''': And how am I to know such things?
* ''Literature/ASeriesOfUnfortunateEvents'' has quite a few ages and timelines that don't seem to fit together. Then again, the BackStory is laden with unreliable information and all sorts of things which make very little sense.
* In the Henry Reed series of books, it may look this way. Aging naturally for the first four books, then rebooting back for the fifth written much later. In reality it was probably a case of NotAllowedToGrowUp. Who cares about sixteen-year-old protagonists when you can contradict your own rules and make him thirteen again?
* Stephen Erikson has some issues with timelines in ''Literature/MalazanBookOfTheFallen''. While, at first glance, everything seems to function fairly well, many dedicated fans of the series trying to put together a timeline of events quickly realized that for the books' narrative to make sense, some events would have had to happen almost a decade after the time they were stated to take place, while others would have to happen before events that chronologically occurred later and, in one case, a particularly important event would have to occur before the events that lead to it. It's quite telling that the books after ''House of Chains'' don't include the date that they take place, because the timeline is a mess. In particular, ''Toll the Hounds'' features a child who is 5 years old and was conceived during the events of ''Memories of Ice'', despite the fact that no more than 3 years have passed during the intervening books.
* Creator/StephenKing
** According to the last couple of volumes of ''Franchise/TheDarkTower'', in which King uses himself as a character, Stephen King was 22 in 1977, despite having been born in 1947. Possibly justifiable in that parallel worlds are of extreme significance in the story, and it's quite possible that the Stephen King of "Keystone Earth" was born in 1955.
** In ''Literature/PetSematary'', Louis Creed is stated to be 35 years old. Later, however, he reminisces about last flying a kite at age 12, "nineteen years ago," which would make him 31. Rachel, meanwhile, is said to have been eight in 1965, 18 years before the beginning of the novel, by which time she and Louis have been married for ten years. That'd mean she got married at 16. Seeing how her father was opposed to the wedding, it seems improbable that she got married before turning 18.
* ''Literature/{{Discworld}}''
** The series intentionally avoided a precise timeline for a long while, meaning that the course of events in the series looked occasionally like a horrible mess, and readers have gone to elaborate lengths to construct a [[http://www.co.uk.lspace.org/books/timeline/dw-timeline-intro.html working timeline]]. Creator/TerryPratchett eventually paid more attention to the timeline, and shrugged off inconsistencies as [[AlternateUniverse alternate pasts via the "Trousers of Time"]]. Eventually, he got right down to handwaving the inconsistencies in ''Discworld/ThiefOfTime'', which established that time has been "broken" before and fixing it all together [[TimeyWimeyBall didn't go as well as hoped]].
** At the climax of ''Men At Arms'', the Gonne fires seven times without a reload despite being established as only being able to hold six shots.
* A case of Editors Cannot Do Math: a line in one edition of ''Literature/GoodOmens'' reads "Sable signed for it, his real name--one word, seven letters. Sounds like examine." Sable's real name is [[HorsemenOfTheApocalypse Famine]], which generally has six letters, not seven. The line reads "one word, six letters" in the original MS, and in all other editions, but somehow ended up as seven in the Corgi edition.
* The three Creator/JulesVerne novels ''Literature/TwentyThousandLeaguesUnderTheSea'' (set in 1866-1867), ''Captain Grant's Children'' (1862-1864) and ''The Mysterious Island'' (1865-1869) take place in the same 'verse, the latter being a sort of sequel to the former two. However, in the latter book, Verne states that the story takes place 20 years after ''20,000 Leagues'', and 12 years after ''Captain Grant's Children''. He even makes up entirely new dates for his previous novels.
* ''Literature/TheNameOfTheWind'' is usually very good with mathematical consistency, but apparently Rothfuss dropped the ball when he was writing the scene where Kvothe takes his University entrance exam. The mathematics master asks for the length of the third side of a triangle with a sixty-degree angle between sides of 3 feet and 7 feet. Kvothe's answer, "Six feet six inches, dead even", is accepted as correct... except that the answer is actually the square root of 37, which is slightly less than six foot ''one'' inch. Even given that he's doing it in his head, he really should have known the answer was closer to 6 feet than 6.5 feet. Since the square root of 37 is irrational, there's no possible way for "six feet six inches" to be exactly correct, unless they use some strange sort of inch that's an irrational multiple of a foot. This was corrected in later editions.
* If you look at the family tree in the last chapter of ''Centennial'', you'll notice that Prudence Wolf (1866-1936) was the mother of Pale Star Zendt (1874-1939).
* Diane Setterfield's ''Literature/TheThirteenthTale'' is an otherwise superb, captivating story. Until, that is, [[InsufferableGenius two highly intelligent characters]] (Setterfield says explicitly that these two are brilliant and gives [[ShownTheirWork numerous legit examples]]) notice a geometric shape in a topiary and argue about whether it is a tetrahedron or a dodecahedron. Setting aside the fact that these are obviously different shapes (tetra = 4, dodeca = 12), the author then mentions that the topiary in question has ''six sides'' and the characters agree it's a tetrahedron!
* Creator/MercedesLackey's ''[[Literature/BardicVoices The Eagle and the Nightingale]]''. Early on, when Nightingale is hired for a job and informed that payscale varies depending on popularity, she's told that the highest payrate anyone's ever earned is a half-royal, equivalent to five gold pieces, and that this is jaw-droppingly impressive. Later, at the same job, she's given a payraise to ''five'' royals.
* Creator/MercedesLackey's ''Literature/HeraldsOfValdemar'' series has some problematic timelines.
** The Tedrel Wars, for example. According to Exile's Honor (p. 68, in the Daw Books paperback) Jadus was a "older than Alberich, approaching middle age" when Alberich arrived in Valdemar. Alberich must then have been at least 25, maybe even 30, seeing as he had been selected at the age of 13, his training in the Karsite military Academy had lasted "long years", and after his training he had spent seven years in active duty in the mounted troops (p. 12-14, 73, 99 in the Daw Books paperback) before he arrived in Valdemar. Therefore, Jadus would have been at least 40, possibly 50, when he fought in the Tedrel Wars some 5-10 years later. In the Arrows Trilogy, he dies of old age. Considering that Healers are readily available, that can't have been before he was 60, making the Tedrel wars 10-20 years ago. Potential problem? Elspeth was born fairly exactly 2 years after the Tedrel Wars, because Selenay married close to the end of her year of mourning after Sendar's death, and conceived very soon after having married. Elspeth is a ''small child'' (based on her general behavior in Arrows of the Queen, maybe 5 or at most 8) when Jadus dies. So "approaching middle age" in Valdemar would be similar to what we mean with "middle age" in our world with modern medicine, and Elspeth should be a teenager or young adult in "Arrows of the Queen", unless Jadus did go to war at the ripe age of approximately 55.
** Another problem comes when you consider Skif. His mentor, Bazie -- who fought in the war -- says that "Wuz back yon twenny yearn, easy, mebbe thutty" (page 104 in the Daw paperback of ''Take a Thief''). A few years later, Skif goes to the Collegium. At this point it's probably about 25 years after the wars, by what Bazie said. Problem? Skif gets to the Collegium before Talia arrives. When Talia arrives, Elspeth is a "small child". Again, she'd be a young adult by that point, and we know that Bazie could count, because he taught all his boys the three basic Rs. Considering Talia is 13 herself and Talia is supposed to bring discipline to Elspeth's life, Elspeth's age really does not add up at all.
* Creator/LoisMcMasterBujold's math is usually spot on, but ''Literature/MirrorDance'' seems to have been shifted from two years after the previous book to four years after late in production. This caused attendant chronological confusion throughout the novel.
* Most of the times and dates discussed in ''Literature/AroundTheWorldInEightyDays'' add up just fine. But in the first chapter, when Mr. Fogg asks Passepartout what time it is, he says it's twenty-two minutes after eleven. Mr. Fogg says that he is four minutes too slow--it is, in fact, twenty-nine minutes after eleven. Where did the other three minutes go?
* Creator/FScottFitzgerald made several errors with the timeline for ''Literature/TheGreatGatsby'': basically whenever a character mentions a number of years, it adds up a different way. The mystique and uncertainty behind Gatsby's past [[AWizardDidIt only partly accounts for it]].
* This is common in the later works by Creator/HarryTurtledove, as noted [[http://turtledove.wikia.com/wiki/Inconsistencies_in_Turtledove%27s_Work here]].
* Creator/IanFleming apparently did not take into account the weight of a bar of a gold, as Literature/{{Goldfinger}}'s plan in his namesake book involves robbing Fort Knox blind (after using an atomic bomb to break open the vault) in just a few minutes. TheFilmOfTheBook thankfully lampshaded this problem, and solved it in a fairly clever way. (Namely, Goldfinger's actual plan is to irradiate all the gold so it's too dangerous to handle. This will take all the Fort Knox gold off the market, causing the price of gold to go up. Goldfinger has a personal stash of gold outside Fort Knox, so he'll benefit a lot from the price increase.)
* Len Deighton ''deliberately'' does this in ''Bomber'', a fictionalised account of a British night-bomber raid in [=WW2=] gone terribly wrong, and the fates that befall the various characters. He sets the action on the night of "June 31st 1943" in order to remove the events of the novel from historical reality, and not only hangs a lampshade over it but practically smashes the lampshade over the reader's head.
* The "Coruscant Nights" trilogy in the Franchise/StarWarsExpandedUniverse has a lot of this. The author intended for it to take place shortly before the original trilogy, but the people in charge decided at the last minute to change it to shortly after the prequel trilogy without bothering with much editing, making many references to past events almost twenty years off.
* At the beginning of ''Literature/SoonIWillBeInvincible'', Doctor Impossible says that there are 1,686 persons with superpowers on Earth and then gives a breakdown by type which sums to 1,778. It's possible there's intended to be some overlap, however.
* In ''Literature/CharlieAndTheGreatGlassElevator'', there are 150 people in the Transport Capsule. Twenty-four are eaten by Knids, and the letter at the end says there are 136 left. This should be 126.
* In Buzz Aldrin and John Barnes's ''Encounter with Tiber'', it's stated that the hexadecimal system counts from 1 through E. Hexadecimal uses the digits 0 through 9 and the letters A through F. One assumes the error was Barnes'; with the computer systems of the 1960s, it's very likely that astronauts would've had to learn hexadecimal. The writers also failed to notice that 4097[[note]]17*241[[/note]] is not a prime number.
* In Greg Bear's ''Literature/{{Eon}}'', the protagonists find a source of an "inverse-square force." A couple of pages later, the force is described as increasing in strength as one got farther from it.
* A calendar hiccup in ''Literature/RemoteMan'' by Elizabeth Honey, features Thanksgiving approximately three-fifths of the way through the book, but sets the climax on November 30th, by which point several weeks have gone by.
* In the ''Literature/InheritanceCycle'', if you bear in mind that Eragon is sixteen when Murtagh tells his back story, then you'll notice that a year disappears in the midst of the same exposition it was mentioned in. Of course, you also have to know that [[spoiler: the two share a mother, meaning that if it was three years after Murtagh's birth that their mother ran away to hide her pregnancy from Morzan, then Eragon couldn't possibly be only two years younger,]] since Murtagh mentions that his most recent birthday was when he turned eighteen. In fact, you may be losing two years in there, but it could be due to {{Retcon}}.
* The narrator of Creator/FrederikPohl's "Day Million" is aware that his listeners are from around "the six or seven hundred thousandth day since Christ." He then identifies Day Million as "ten thousand years from now." Even assuming that his earliest estimate is correct (which would be well before the story's 1966 publication), that makes only forty days to a year. Granted, it could be just the impatient LemonyNarrator's carelessness, but you would think at least that fellow author and praising commentator Creator/RobertSilverberg would have something to say about it.
* There's a glaring example in the ''Weather Warden'' book series by Rachel Caine. The lead character, Joanne, has a supernatural adult daughter named Imara, who technically doesn't age. In the fifth book, Firestorm, a character comments to Joanne that she is "plenty old enough" to have an adult daughter. Joanne's character is ''twenty-eight'' years old, there's no way she could have an adult daughter. Suppose Imara is twenty years old; that would mean Jo had her at eight years old. Granted, girls as young as five giving birth have been documented, but the clear implication of the above statement is that Jo is old enough to have had a child at a typical age long enough ago that that child would be an adult.
* ''Threshold'' by Caitlín R. Kiernan contains a rare attempt of an author to include mathematics higher than arithmetic, but unfortunately falls headlong into this trope. The book lists a regular heptagon (a seven-sided polygon with all sides and angles the same) as an {{Alien Geometr|ies}}y based on the fact that a regular heptagon is not constructible. However, in geometry, "not constructable" means "cannot be drawn with only a straight edge and compass." It does not mean "cannot be made with any tool known to man" (you can draw a regular heptagon just fine if you have an accurate protractor and ruler) and most definitely doesn't mean "cannot exist in nature" or "seeing one will cause you to GoMadFromTheRevelation."
* In ''Literature/LeMorteDarthur'', [[Myth/KingArthur Lancelot]] faces a dozen armored knights while unarmored himself. He kills one of them, takes his armor, then kills "the remaining twelve." Malory takes the trouble to name each one individually, so you'd think he'd have remembered to decrement the count.
* In ''The Poisoned Chocolates Case'' by Anthony Berkeley, a character enumerates twelve conditions the criminal must fulfill, and states: "The mathematical odds against their all being fulfilled in one person are... 479,001,600 to 1. And that, mark you, is if all the chances are even ones." Two errors here. Firstly, 479,001,600 is 12 factorial, but he should be calculating two to the twelfth power -- 4,096. Secondly, those are the odds against ''any particular'' person fulfilling all the conditions, which is completely irrelevant -- after all, assuming he's correct in saying that the crime must have been committed by someone fulfilling all twelve conditions, the probability that ''someone'' fulfills all the conditions is 100%! The question should be, "What are the chances that, given that a particular person fulfills all the conditions, that person is the criminal?" -- and the answers to the two questions will not, in general, be the same. [[ProsecutorsFallacy This particular fallacy]] is common with real-world prosecutors too. "The chance that the defendant's DNA would match that found on the crime scene by pure chance is less than one to a million" sounds much more convincing than "The defendant is one of ten or twenty people in the New York metro area whose DNA match".
* The framing story of the ''Literature/ArabianNights'' is stated to take place "during the time of the Sasanid dynasty" -- that is, no later than the 7th century A.D. Many of the internal stories that Shahrazad tells take place during the reign of the caliph Harun al-Rashid, more than a century after the collapse of the Sasanid empire.
* "Lord of the Wolves" by Creator/AlexandreDumas is a horror story about a man who is granted unholy powers. However, the first time he uses them, one hair on his head turns fire red. The second time, it happens to two hairs, the third time, to four hairs, and so on. At one point in the novel, it is stated that more than half of his hairs are red. He proceeds to use his powers a few times more, and by the end of the book, only one single hair on his head remains normal. The problem is, if you add 1 + 2 + 4 + 8... together, the number of red hairs almost exactly doubles with every use of the power. So if it is stated that more than a half of his hairs have been turned "evil", he gets one more use of the power ''at most'', and no hairs on his head would remain unchanged. This is especially jarring as it would not impact the plot in any way if the amount of hairs changed into red mid-novel was realistic -- not all uses of the character's powers are listed explicitly, all that matters for the purpose of the plot is the single remaining hair by the end.
* In Creator/LouisSachar's ''Literature/WaysideSchool'' series, Wayside School has thirty classrooms, but the total number of students is given as ''4500''. That would be an average of 150 students per classroom, and since we know that the 30th classroom has 29 students...
* In ''Literature/EndersGame'', Bonzo Madrid commands Salamander Army for the entire time Ender spends at Battle School, which lasts about three and a half years. This requires either that Bonzo made commander impossibly early (younger than Ender himself does), or that he is long overdue for graduation when he fights Ender in the shower (which Graff explicitly denies is the case just a few pages earlier).
* Creator/LewisCarroll was one author who was actually very good at maths: he was a maths teacher at Oxford. A lot of logic puzzles were worked into his two most famous books.
* Although a scientist, Creator/IsaacAsimov clearly didn't do the math when it came to Trantor, the planet covered by one city in the Literature/{{Foundation}} trilogy (and the inspiration for Coruscant in ''Franchise/StarWars''). Trantor's population at its height is given as over 40 billion in a single city covering all 75 million square miles of the planet's land area: assuming 45 billion people, this works out to 600 people per square mile, or roughly equivalent to the United Kingdom instead of a city like Manhattan (which has more than 65,000 people per square mile). However, the city is also explained to go a mile down: the available area increases significantly. If there are only 100 levels underground, actual population density drops to 6 per square mile. The problem with Trantor isn't overcrowding, it's finding someone else to talk to. Maybe he used the [[http://en.wikipedia.org/wiki/Long_scale long scale]]? Even with other planets being used to supply Trantor with food (and probably remove the garbage) there have to be some pretty sizable facilities for processing, transporting, and disposing of everything. Most major cities try to locate as many of the power plants and water treatment centers outside city limits, but they still take up room somewhere. Even if every inch of the planet is covered in buildings, its impossible for anywhere near 100% of them to be residential structures. The prequel books indicates that relatively large areas of the planet ''are'' taken up other things than residential structures -- power plants, yeast-food production, infrastructure, etc. The Psychohistorians itself gives three examples of relatively large, sprawling non-residential complexes: the University, the Palace and the spaceports (those giant food-transports have to ''land'' somewhere, after all!). Still, there doesn't seem to be enough to bring Trantor up to city-level population density.
* Quentin Compson's age in ''Literature/AbsalomAbsalom'' From ''The Sound and the Fury'', we know that he commits suicide in 1910. So when Rosa Coldfield first tells him the story, shortly before he goes to Harvard, the year must be 1909. The narration says that Quentin is 20 at the time. But in the appendix, there's a timeline with the birth and death dates of major characters, which says that Quentin was born in 1891 (and corroborates the date of 1910 for his death). For his roommate, we get the birth year of 1890. "Shreve was nineteen," the narration says (which is possible), "a little younger than Quentin" (which is not).
* The 14th century English monks of Crowland Abbey successfully fended off another abbey's attempt to acquire some of their landholdings in court, presenting as evidence a large book alleged to document their historical claims to the property. Apparently the Crowland monks had succumbed to temptation, and to this trope, because the book has since been recognized as a fraud, not least because some of the senior monks mentioned in its history were alleged to have served at the monastery for as long as ''148 years''.
* Faye Kellerman's Peter Decker series has been playing a bit loose with Decker's age in order to keep him out of retirement. In the first book, which was published in 1986 and presumably takes place no later than that year, Decker was described as 38-years-old and a Vietnam vet. Rina's two sons are seven and eight. By the 2010 book ''Hangman'', the sons are still in college and Decker is just turning 60. You do the math [[note]]It is 24 years between 1986 and 2010 which would make Decker 62, close to the age given, the real issue is that the sons would be 31 and 32 respectively, or when factoring in the two year dilation, 29 and 30.[[/note]].
* A failure to account for the SquareCubeLaw resulted in some ships in ''Literature/HonorHarrington'' of the stated mass and dimensions being about as dense as smoke. The stated dimensions were cut by about 2/3rds in later editions to correct for this.
** In ''Echoes of Honor'', a velocity is given as "about four thousand KPH [kilometers per ''hour''] -- make it sixty-seven KPS[kilometers per ''second'']" -- oops!
** One source puts missile acceleration figures as x-thousand [=KPS2=]. It's g's, not [=KPS2=], and the conversion factor is not even close to 1. A really bad mistake, as the missiles would come close to the speed of light with those acceleration figures, and the whole MDM technology would be ''utterly'' redundant.
** In the same book, a more subtle error is in the missiles which "accelerated at four thousand gravities." That means they fly a distance of 20km in the first second. They are locked-on manually, and there are six of them in the air at the same time. Assuming launch intervals of only two two three seconds ("Target Two up!" -- "Launch Two!" -- "Two away!" is spoken), that's at least ten seconds between the first missile and the sixth. And a distance of 2000km assuming constant acceleration. Even more importantly, an impact velocity of 400km/s, which would make them effective kinetic weapons -- although Weber writes that they are not. (Certainly not at peak efficiency, but equally certainly effective.)
** In ''Mission of Honor'', 9000 treecats (and quite a lot of humans) are killed, which is represented as "close to 1% of twelve million." It is stated twice, and it's a plot point. 90,000 would be reasonably accurate (though rounding up quite a bit), but 9000 is less than 0.1%.
* Most of the dates in the journal entries of Bram Stoker's ScrapbookStory ''Literature/{{Dracula}}'' make no sense when compared with characters' descriptions of events in the text.
* In ''Literature/{{Helm}}'', there are two notable inconsistencies with ages:
** Marilyn de Noram is first described, through Leland's eyes, as a young woman who "couldn't have been much older than Leland" (two years older, it is later revealed). Later, Dulan de Laal says that Dillan de Laal is "fifteen years older" than Marilyn. In the family tree at the beginning of the book, Leland is 17 and Dillan is 27.
** It is said that when Dulan was 25, Dillan was 2 and Dexter "a slight swelling in his mother's figure". Dillan is in fact listed as three years older than Dexter (27 and 24), but Dulan is listed as 52 -- two years older than this would imply.
* O. Henry's "Literature/TheGiftOfTheMagi" begins 'One dollar and eighty-seven cents. That was all. And sixty cents of it was in pennies.' That leaves $1.27 containing no pennies. There were also two-cent and three-cent coins, which were more recent than the half-cent and thus more plausibly still found in circulation.[[note]]The half-cent was minted until 1857, the two-cent until 1872, and the three-cent until 1889; the story was published in 1905[[/note]]
* Deliberately invoked in the Literature/DoctorWhoNewAdventures novel ''Conundrum'', which is set in a fictional pocket dimension. The Doctor is playing Scrabble and his opponent makes an excellent move which, as the Doctor points out, ''cannot be made on a standard Scrabble board''. And then glares at the 'writer' for making a mistake.
* ''Literature/FiftyShadesOfGrey'':
** Ana graduated on Thursday, May 27, 2011 (according to various emails, although in the real world, May 27, 2011 was a ''Friday'') and then had interviews four days later on Monday, May 30. 27 + 4 =/= 30 in base 10. Monday would have been May ''31''--Memorial Day, a federal holiday in the United States on which most business offices would be closed.
** There's simply no way that Ana can interview Grey on Monday, May 9, 2011 (the date given in ELJ's short story ''Meet Fifty Shades''), have five days pass, meet Grey in the hardware store in which she works on Saturday (which would be May 14), have "several weeks pass"--so three weeks at the very least--have a week of finals and then graduate on May 27. Any way you look at it, you can't squeeze five weeks between May 9 and May 27 without a time machine.
** The date of the interview changes in ''Grey'', which is ''Fifty Shades of Grey'' from Christian Grey's point of view. The book's chapters are dated and Chapter One, the interview chapter, is titled "May 11, 2011." Why the date was changed is unclear, as it gives events even ''less'' time to occur and makes the still-canonical five-day gap between the interview and Grey's visit to Ana's place of employment on Saturday, May 14, 2011 impossible.
** In ''Fifty Shades Freed'', Grey refuses to marry Ana any later than one month after his birthday (his birthday being on June 18, so the deadline for the marriage would be July 18). Since he nearly always gets his way (and has terrible temper tantrums when he doesn't), it seems likely that they married on July 18, if not before. Yet Ana can't remember how long she's been married. She mentions multiple times on the same day that she has been married for two weeks, three weeks, and a month. Even a week after this, when their honeymoon has ended and Grey and Ana are back in Seattle, Ana still insists that she has only been married for three weeks...as if time itself had stood still.
* ''Literature/ASongOfIceAndFire'':
** George R. R. Martin often creates a one-year confusion by using the “in his Xth year” formulation.[[note]]Technically, a person’s 17th year is the year they are 16--the year ''leading up to'' their 17th birthday--but in current usage it rarely means anything other than that the person is ''now'' 17.[[/note]] For instance, Jaime Lannister is claimed to have been elected to the Kingsguard in his 15th year. However, whenever his age is referred to, the book clearly says 15.
** Martin also [[http://www.westeros.org/Citadel/SSM/Entry/Size_of_Westeros/ intentionally avoids]] being specific about distances because he knows he would get the math wrong and readers would complain. He still seems to fail a bit on SciFiWritersHaveNoSenseOfScale as he talks about large, heavily burdened groups (armies, the royal convoy, etc) covering "thousands of leagues" (1 league = 3 miles) in a matter of days; at a slow walk on horseback thousands of leagues should take months.
** InUniverse, Samwell Tarly points out that the books in Castle Black are all suspect about their historical accuracy, as the kings in them rule for hundreds of years and they talk of knights centuries before the Andals came to Westeros.
* In ''Literature/SkulduggeryPleasant'', Valkyrie ages by one year each book for the first few books. In books 1 to 5 she ages from 12 to 16, (the third book specifying she's has ''just'' reached 14) but each book lasts a period of less than a month, and the gap between each book is often less than a year. Some specific examples were mentioned; the gap between books 2 and 3 is 6 months, 3 to 4 is 11 months, and 4 to 5 is 5 months, meaning Valkyrie aged from approximately "13 and a half" to 16 in a period of 22 months.
* In ''Literature/TheFaultInOurStars'', Hazel incorrectly believes that the infinite set between zero and two is larger than the infinite set between zero and one. However, WordOfGod states that it was intentional, as he didn’t want his characters to always be right. Also, Creator/JohnGreen is so inept at mathematics that he has a ‘resident mathematician’, Daniel Biss, whom he calls -- sometimes in the middle of filming -- to clarify an equation.
* In the ''Literature/NightHuntress'' series by Jeaniene Frost, Annette says she was 14 when she was forced into an arranged marriage, and met Bones "several years" after. If we conservatively call "several" three, she was 17. She conceived a child ''after'' that, as she states that the father could have been either her husband or Bones. So we have her giving birth at probably 18 or older. She describes being ill for months following the breech delivery, during which time Bones helped her recover. Then she relates his being sent to Australia and returning 19 years later to make her a vampire. So she was ''at least'' 37. But the same book states her age as being 36 when she was turned. This works only if we take "several" to mean "two." Which it really doesn't.
* Though details of character ages are mostly left vague in ''Literature/ChroniclesOfMagravandias'', there are clues. And those clues don't always line up with the explicitly stated ages.
** At one point Almorante is stated to be thirty-six. Context clues would put his younger brother Bayard at thirty-five or so and at best Bayard and Mante have one (two if you count the son that died) brother between the two of them.
** Where exactly does Bayard fall in the line of succession? Without any other princes dying, he's sixth in line in the first book and fourth in line in the third.
** Linnard's age makes no sense. In ''Sea Dragon Heir'' Tatrini explicitly states that Gastern is not yet married. By ''The Way of Light'', four years later, he is married with a child, only Linnard is written as being of an age with his eleven-year-old uncle.
** The number of the emperor's sons never seems to change, even though in the beginning of ''Sea Dragon Heir'' when they were first mentioned, the youngest ones wouldn't even have been born yet.
* Averted in Creator/GregEgan's works, which shouldn't come as any surprise given that he holds a [=BSc=] in mathematics. Stripped of plot and characters, ''Literature/{{Diaspora}}'' would make a fairly good introduction to topological groups.
* In ''[[Literature/MaryRussell The Beekeeper's Apprentice]]'' by Laurie R. King "[[Franchise/SherlockHolmes Mr Todd]]" is told he's a shilling short in payment and counts out "three pennies, a ha'penny, and six farthings". Three plus one half plus six quarters equals five, but there were 12 old pence in a shilling. Fixed in later editions, where it's ten pennies instead of three.
* In the Bone Chillers book ''blowtorch@psycho.com'', main character Jason is a leapling, born on February 29. Multiple characters, Jason included, mention how Jason's "lucky thirteenth" birthday is in a leap year, so he could celebrate on his actual birthday. Apparently, no one in this book has any idea how a calendar works; a leap year occurs every four years, so a leapling's thirteenth birthday would fall in a common year.
* ''Literature/TheAdventuresOfArchieReynolds'' throws out lots of numbers, measuring the number of minutes that an action was performed, the exact size of something, etc. However, the numbers don't add up. Characters have celebrations that last minutes or even hours, characters stand around and watch people for minutes instead of seconds, and objects are sized very oddly.
* ''Literature/{{Twilight}}'' has a bad case of this. The most prominent example is the author appearing to have no idea how long driving from one place to another would take. There is an attempt to justify it by establishing that Edward DrivesLikeCrazy, but even then there are moments that are suspect. The most egregious example would be the claim that Edward and his brothers drove from Forks, Washington to Alaska in 16 hours, which would not only require them to be driving at ludicrous speeds without stopping for gas or anything, but is likely not even possible given the very nature of the main highway. The road to Alaska is so long, treacherous, and remote that getting there requires going through checkpoints, where they'll send somebody to look for you if you don't reach the next checkpoint in time.
** In Breaking Dawn, Carlisle states that Renesmee's growth seems to be slowing down after she is born. This is a child that spend a month in the womb, thus gestating at nine to ten times the rate of a human baby; then, three to four months after she is born, she apparently looks about five. That means that after she was born, she grew at twelve to fifteen times the rate of a human child.
* In ''Literature/TheHungerGames: Catching Fire'', Katniss describes the Cornucopia as being 40 yards away from the launch platform, which is located in a circular lagoon. There are twelve spokes of land separating the 24 tributes, and Katniss is equidistant from the land strip and the adjacent tribute platform. If you do all the calculations, it turns out that Katniss is about seven yards from the nearest land strip. Katniss has to swim this distance, and describes it as "a longer distance than [she's] used to swimming" back in the lake outside District 12.
* in ''Literature/LadyOfTheLake'' when Logde of Montecalvo votes whether or not [[spoiler: let Ciri see Geralt]], before Filippa gets to vote one of the sorceresses says it's a draw. Actually counting the votes show that it's not, there were 5 votes for and 4 against.

[[folder:Live Action TV]]
* ''Series/BuffyTheVampireSlayer'': Creator/JossWhedon has stated that he sucks at math. Among other things, Spike has miraculously managed to become younger with each passing season:
** In season two, he is stated by Giles to be "barely 200." In season four, Spike tells Willow that he's "only 126." Finally, in season five, the flashback episode "Fool for Love" established Spike as having been changed into a vampire by Drusilla in 1880. As the episode was made in 2000, this would make him 120 in vampire years. We don't know precisely how old he was when he was vamped, but it's more than six and less than eighty.
** In Season 1 and 2, Angel is mentioned as being 240 and 241, respectively. Those seasons took place in 1997 and 1998, meaning he was born between 1756-1758 (depending on when his birthday is). However, the flashback in Becoming: Part II shows him being sired by Darla in 1753.
** Buffy herself has at least three different birth dates, although this is more about continuity than math. In a season 1 episode, we see her school details on a computer screen, with two different birthdates, in 1979 and 1980 (the screen display changes between cuts). Then her gravestones (in the season 1 Nightmares episode, and at the end of season 5) show her birth date as 1981. Besides this, she also said in a season 4 episode that her astrological sign was Capricorn on the cusp of Aquarius, which puts her birthday on or soon before January 19 (which does not fit either of the season 1 birthdays).
** In the third season episode Anne, Buffy is taken into a hell dimension where time passes very swiftly. The demons who run the dimension kidnap people from Los Angeles, and put them to work in the hell dimension. After many decades of work, the workers, aged beyond recognition, are returned to L.A., where they have only been missing for a day or two. We see maybe two dozen human workers in the hell dimension, and if each lasts (generously) about two days objective, the demons have to be kidnapping at least six people a day, and dumping about the same number of bodies. Unless there are multiple feeder sites for the hell dimension, which the evidence in the episode does not support, people are going to notice 6 people a day disappearing, even in L.A.
** In season 7, the episode "Conversations With Dead People" dates itself as November 12. The next three episodes each pick up exactly where the last ended, and we only go through a couple of days, yet in the fourth of this series it's suddenly December.
** In "After Life" Spike tells Buffy she's been gone 147 days, or about 5 months. In later episodes, however, there are numerous references to her only having been gone about 3 months.
* It happens with the ages of the Series/{{Friends}}. For example, Ross's birth date doesn't match with his purported age and his birth date changes throughout the series. The same problem appears when the matter of who is older ensues.
** Rachel's LongestPregnancyEver also counts.
** Possibly the funniest is that Monica and Rachel were stated to be twenty-six in the pilot, but they didn't turn thirty until season seven.
* ''Series/GameOfThrones'':
** In the interest of epic battle scenes, the number of people killed on-screen may not match up with statistics about the battle:
*** The Season 4 battle at Craster's Keep was against eleven mutineers. Jon Snow personally kills eight, Ghost another, and Locke another. Apparently the rest of the Watchmen only kill one mutineer between them?
*** The episode "The Watchers on the Wall" features a battle between the Wildlings and the Night's Watch. The previous episode states that there are only 102 watchmen in Castle Black. There seem to be considerably more depicted in the episode. To wit, a conservative count shows 41 watchmen killed on-screen. This assumes that no watchmen died on the ground while the cameras were focused atop the wall, or while Slynt was running to the pantry, or during Alliser's duel with Tormund, etc. It also assumes Ygritte missed every shot that didn't cut to her target getting hit, which was most of them. It's ultimately subverted; a later episode establishes that they indeed lost fifty men, including most of their dedicated warriors, utterly devastating them as an organization.
** Cersei and Jaime's age is inconsistent. Tywin Lannister was Hand to King Aerys II for 20 years before Robert's Rebellion, but Cersei, who became queen at 17 following the rebellion, remembers when he was appointed. In Season 4, Cersei says she has been queen for 19 years, which added to 17 would make her 36, but her twin Jaime was said to be 40 in the season premiere.
* ''Series/{{Heroes}}'': Adam was around thirty when he was seen in 1671, which would make his birth year around 1640. But in a season 1 episode, "Takezo Kensei's" date of birth is given as 1584. Even accounting for the fact that Adam was a bald-faced liar, no one in their right mind would have mistaken him for an 87-year-old man. Especially since he didn't know yet that he didn't age. Of course, the season 1 thing could be hand-waved as an in-universe historical mistake, since Takezo Kensei is a legendary figure and since he was actually a cowardly English con-man (while everyone thinks he was a brave and magical Japanese warrior), the real details of his life were never known. There's also the point that it's implied that the majority of the Kensei stories never really happened, but were instead made up by Yaeko to create a StableTimeLoop. Within this context, it would probably make sense for her to backdate the events slightly to avoid awkward questioning of the legend. However, if this was true, Hiro would never have expected 1671 to be Kensei's time in the first place.
* ''Series/ThirtyRock'': Liz somehow aged from 35 to 37 between two birthdays.
* ''Series/StargateSG1'':
** Catherine Langford says she was twenty-one in 1945. This would make her four in 1928, yet ''Film/{{Stargate}}'' shows her to be much older (probably about twelve) in that year. Of course, this is hardly the only inconsistency [[AlternateContinuity between the film and the series]].
** In the episode "Between Two Fires", Carter (of all people) calculates that they'll need 38 Ion Cannons to defend the planet without any blind spots. While 38 would definitely get the job done, you can eliminate all the blind spots on a sphere with as few as 4 viewpoints.
* ''Franchise/StarTrek'':
** There is an official mathematical formula for calculating how fast warp speeds actually are (different ones for TOS and TNG eras). However, if you look at the instances where distance, warp factor and time to arrival are all mentioned within the various series, it seems like [[TravelingAtTheSpeedOfPlot none of the writers bother with the formula]]. One of the more glaring examples is the ''Series/StarTrekEnterprise'' pilot "[[Recap/StarTrekEnterpriseS01E01E02BrokenBow Broken Bow]]", where the ship is said to be limited to warp 5 but can reach the Klingon homeworld in a week, which ought to put Qo'noS somewhere in the Sol system's Oort Cloud by the TNG scale. (It's further but still way too close to make sense by the TOS scale.)
** ''Series/StarTrekTheOriginalSeries'':
*** In "[[Recap/StarTrekS1E20CourtMartial Court Martial]]", Kirk sets the computer to increase sound by a degree of "one to the fourth power." He, of course, presumably meant to say "one '''times ten''' to the fourth power", or possibly, "ten" ''instead of'' "one": "ten to the fourth power" (either of which is obviously better than simply saying "ten thousand"). ''One to the fourth power'' equals... one.
*** In "[[Recap/StarTrekS1E23ATasteOfArmageddon A Taste of Armageddon]]", the power of a weapon is given as "Decibels - 18 to the 12th power". Setting aside the usual objections about sonic weapons in space (since Decibels can be used to measure any sort of power, and 'sonic' could just mean low frequency), we are left with the observation that not only has the writer bizarrely switched to base 18 (we'd usually say four times ten to power 22), but the writer is apparently unaware that decibels is a logarithmic scale. We have a power multiplier of 10 to power ((18 to power 12) / 10), which is a number far too big for the average scientific calculator, and vastly more power than the entire luminosity of our galaxy.
** ''Series/StarTrekVoyager'':
*** ''Voyager'' should have run out of torpedoes way before the end of the show based on the few times there was an inventory count mentioned in dialogue, but they somehow were able to keep firing them. They never seemed to run out of shuttles either: In one late season, Chakotay states that they have a full complement of shuttles despite at least three getting destroyed on-camera. Though it's implied by the construction of the Delta Flyer that the crew was rebuilding shuttles and likely torpedoes offscreen, and the ''Star Trek TNG Writer's Technical Guide'' states that ships have on-board industrial replicators to create standard parts of this nature.
*** Even worse, and crossing into ArtisticLicenseBiology, is the Ocampan reproduction system. Each female can become pregnant and give birth once in her life, and every birth we know of was single, no twins triplets etc... Even if every single female succesfully conceived and delivered a baby at that time, they'd still have a radically declining population. Which, coupled with an Ocampan generation being about 3-4 years, means that with those numbers the entire Ocampan race should become extinct in about the life span of an average 24th century human.
* In the first series of the new ''Series/DoctorWho'', Rose travels back to November 1987, where we see her as a baby of about six months old (according to series 2's "Rise of the Cybermen") -- except there are repeated references to her being 19 in her first season, which starts in March 2005.
** The Doctor's own age, on the rare occasions he mentions it, frequently changes by implausible increments (and at least once went ''down'', between the last time it was mentioned in the classic series and the first time it was mentioned in the revived series). Steven Moffat, the man in charge from 2010, has openly admitted that "in his mind," the Doctor has lost count and says 900 (bumped up to 1200 during the Eleventh Doctor's run) because it sounds coolest. Also from Moffat, "this is a man who logically should have no idea how old he is."
-->'''The Doctor''': Uh, I dunno. I lose track. 1200 and something, I think, unless I'm lying. I can't remember if I'm lying about my age, that's how old I am.
** In the classic Doctor Who story, [[Recap/DoctorWhoS6E2TheMindRobber The Mind Robber]], after hearing that a man wrote 5,000 words a week for 25 years, Zoe exclaims "but that's over half a million words." Technically, it is though, by 6 million.
** Going to the very first episode of the series (1963's [[Recap/DoctorWhoS1E1AnUnearthlyChild An Unearthly Child]]), what is clearly supposed to be the quadratic formula is seen on a chalkboard in the background. However, the denominator is written as 2ab instead of the actual 2a.
** In a kind of cross between this and ArtisticLicensePhysics, during [[Recap/DoctorWho2005CSTheChristmasInvasion The Christmas Invasion]] the Doctor's hand gets cut off. He can still regenerate it though, because he's still within the first fifteen hours of his regeneration cycle. Except that he arrived in London on Christmas Eve, while it was still light, and his hand gets cut off the next day, also during daylight hours. Christmas is only a few days after the winter solstice, and the night lasts longer than fifteen hours in London at that time.
* Ron Moore's [[WatsonianVersusDoylist standard explanation]] for chronological inconsistencies in ''Series/{{Battlestar Galactica|2003}}'' is that he's bad at math.
* ''[[Series/TwentyFour 24]]'': The first season takes place "two years to the day" after Jack Bauer led a covert strike in Yugoslavia during the 1999 Kosovo War. It is also a presidential election year. [[note]]Presidential elections in USA are held four years apart, and the count started in 1788. You can't ''have'' a presidential election in 2001; the writers either missed the 2000 elections or anticipated the 2004 ones. Or, like ''Series/TheWestWing'', ''24'' takes place in an alternate timeline in which the elections occur on a different schedule.[[/note]]
* ''Franchise/{{Degrassi}}'', in all its incarnations, is ridiculous when it comes to this:
** In the 7th episode of the first season of ''Series/DegrassiJuniorHigh'', Wheels is said to be 14. He has a birthday in the 12th episode of that season. In the first episode of the 3rd season, he is said to be "almost 15", and stays that way until a month after the 11th episode of that season (which was most of a year after the first).
** Spike has baby Emma at the end of the second season of ''Series/DegrassiJuniorHigh'', which is the end of grade eight for Spike. So, when Spike graduates, Emma should be approximately four. At Spike's ten-year reunion in the first episode of ''Series/DegrassiTheNextGeneration'', Emma is only twelve. In fact Emma should have been ''five'' when Spike graduates, because of the extra year (below).
** In the first episode of ''Series/DegrassiTheNextGeneration'', the class reuniting is said to be the class of '91 -- even though the classes reuniting (yes, there are two classes reuniting for some reason) should be the classes of '92 and '93, respectively. The writers seemed to have based this off when ''Series/DegrassiHigh'' ended, not taking into account that it ended with the characters in years ten and eleven.
** At the time the original series was made, Ontario schools had an extra year in the college-preparatory track. This explains why most characters in the "School's Out" special are identified as 19, while [[spoiler: Caitlin]], who graduated a year early, is 18. The writers promptly forget this detail as Spike talks about Emma entering Junior Kindergarten, making her 4 while her mother is 18.
** After [[spoiler:J.T.]]'s death, he is said to have been born in 1990, making him sixteen at the oldest. He was in year twelve, in which you are normally seventeen or eighteen.
* Certain aspects of ''Series/TheMiddleman'''s timing are... odd, though probably not outright contradictory. Consider the following:
** The show seems to be set in 2009. Middleman '69 says he's been in cryo for forty years. Also, Wendy and Lacey have known each other for five years and met as freshman, and Wendy watched Voyager 2 pass Neptune (in 1989) when she was three, which would likely put her in the college class of 2008.
** The Middleman was on his high-school football team in 1991. Presumably he was at least sixteen then, so he's at least 34 now.
** Sensei Ping first defeated a hundred men when he was twice the Middleman's age. So he's at least 68 (and defeated those hundred men when he was at least 68; given how casual he is about the idea now, there's a decent chance he's a lot older). This is kind of weird on its own, especially since he doesn't look anywhere near that old, but maybe that's why he doesn't want people asking about his age. However, he's also been training in martial arts for "two of [Wendy's] lifetimes", and she's 23. He must therefore have been an adult ''before'' he started training.
-->'''The Middleman''': Never ask Sensei Ping [[PlayingWithATrope about his age,]] the [[ChekhovsGun wrestler mask]]...
-->'''Wendy Watson''': Or the clan of the pointed stick, [[SchmuckBait I know.]]
* ''Series/TheOC'': In season one, Marissa's little sister Kaitlin is referred to by Seth as a fifth-grader, yet when [[PutOnABus the bus returns]] in season three, she's already in eighth grade, and looks even older, though strangely enough for a series heavy with DawsonCasting, ''she wasn't'' -- the actress turned fourteen shortly after her first episode aired.
* On ''Series/AllMyChildren'', Kendall Hart was introduced in 1993 as Erica Kane's 16-year old daughter, who Erica gave birth to at nearly 15 years old. Erica and her mother, Mona, placed Erica's baby girl for adoption to the Harts. Since the storyline established Kendall as 16, this would've made her mother, Erica, in her early thirties. However, Erica had been older than that for at least a decade. Once the writers were called out on this, they quietly {{Ret Con}}ed Kendall's age from 16 to 22/23 years old some time later -- which was still pushing things, but [[WillingSuspensionOfDisbelief somewhat acceptably so]] (nonetheless, this didn't stop the writers from continuing to write Kendall like a bratty teenager who practically hugged her dolly at night). It also led to the classic example of Inverse Dawson Casting: The change meant that 16-year old Sarah Michelle Gellar was playing a twenty-something. However, all this rapid aging was undone when the character returned to the show in the form of Alicia Minshew six years later and Kendall's birth year was reverted back to what it originally was when she first appeared as a 16-year old girl in 1993.
* ''Series/CriminalMinds'':
** In one episode, Aaron Hotchner recollects meeting his wife when she was a tenth grader and he a junior. The impetus for his memory is a yearbook: "Reflections 1987." If Hotch were a seventeen-year-old junior, that would make him born in 1970, and thus approximately 35 at the time of the episode. Previously, viewers were told that Hotch had been a prosecutor before joining the FBI. So, if he graduated high school at eighteen, then college at 22, then law school at 25, and immediately became a prosecutor, then maybe he could join the Bureau at 27. That gives him eight years to not only be promoted to the BAU, but to become the Unit Chief. Considering how hard the BAU is to get into, a fact which the show points out, that seems... unlikely.
** A year later, Agent Rossi is introduced. It's said that he last worked for the BAU ten years before, and that Hotch was on the team with him. Meaning that Hotch would have had to join the ''BAU'' at age 27, and thus the FBI itself decidedly earlier, meaning he would have to... oh, we give up.
** In a later episode, Hotch's medical chart lists him as being 43, four years older than his yearbook leads us to believe. Or maybe three years older, if it was his ''wife's'' yearbook.
* In ''Series/KathAndKim'' flashbacks show Kath being pregnant with Kim in the seventies, while Kim, Sharon, and Brett are teenagers in the eighties. Considering the show (aired from 2002) was set in the present day, Kim ought to have been born around 1978 and met Brett in the mid nineties. Rather than actually failing at math, the writers probably just thought the eighties were a better source of jokes (regarding fashion and whatnot) than the nineties.
* You think a show that relies so heavily on {{Flashback}}s and [[TimeShiftedActor Time Shifted Actors]] as ''Series/ColdCase'' would be free of this, right? Wrong! The conflicting data about the age of the most senior detective, Will Jeffries, was eventually {{lampshade|Hanging}}d in sixth season episode "November 22nd":
-->'''Will:''' [talking about the day Kennedy was assassinated] I was playing touch football at recess.\\
'''Scotty:''' Recess? I thought you were, like, forty-five when that happened.\\
'''Lilly:''' No, you're thinking of when Lincoln was shot.\\
'''Will:''' Keep it up. See what happens.
* In ''Series/VeronicaMars'', Logan Echolls finds out that his late mother's trust fund is running low unexpectedly. He's told that it's going to run out in fourteen months at this rate, but it turns out that it's only losing ten thousand dollars a month more than expected. The idea that his losing one-hundred and forty thousand dollars means he'll be broke in a little over a year doesn't mesh well with his continuing stereotypical rich-kid lifestyle nor the subtext suggesting that he noticed the missing money because he's actually being financially responsible.
* ''Series/{{Bones}}'':
** In one episode, it's revealed that Brennan had a relationship with her advisor in Chicago when she was 24. In another episode, she's said to have been born in 1976, and been working at the [[FictionalCounterpart Jeffersonian Institute]] since 1998 (when she would have been 21 or 22). In another episode, she talks about identifying bodies after the Branch Davidian siege. Which means that she was at least 23 by 1993.
** In another episode, Angela kept asking her co-workers to donate money to save a cute piglet from becoming bacon. She claimed doing this would cost $1500, yet if buying and rearing pigs cost that much, pork would cost a ''lot'' more than it does. A whole pig that's already dead costs [[http://www.obriensfamilyfarm.com/prices.html about half that]].
* Johnny Drama's age in ''Series/{{Entourage}}'' rises and falls between episodes. In some, he was in high school with Vincent, his younger brother, putting him at about three years older; in others he could drive and legally buy liquor while his brother was still in grade school.
* ''Series/{{NCIS}}'' is pretty bad for this. Gibbs's backstory features a hilariously implausible timeline and Tony's age changes every other time it's mentioned. In ''Series/NCISLosAngeles'', G. Callen was in foster care from a very young age until, presumably, he was eighteen. During that time he was in 37 foster homes. All right. However, the longest he ever stayed in any home was three months. Even if he stayed in the other 36 homes for two months and 29 days each, that still doesn't come anywhere close to a minimum of thirteen years. And it's specifically mentioned that he usually only spent a few weeks to a matter of days in each place.
* ''Series/{{Eureka}}'' has time travel between 2010 and 1947. The time travel is explicitly said to be possible only when an eleven-year solar flare cycle is at its peak. 63 years are between the two points, too many for five cycles but not enough for six. Solar cycles average at around 11 years. Six cycles happening in 63 years is not out of the question. That being said, it was still wrong. There was a peak during 1947, but 2010 had a low sunspot activity.
* ''Series/{{Charmed}}''
** The show has a demon who appears every [[ArcNumber 1300 years on Friday the 13th (who conveniently shows up in the thirteenth episode of the series, looking to kill thirteen unmarried witches)]]. But in the seventh century AD, when he would have last appeared, our currently-used Gregorian calendar wasn't even a twinkle in Pope Gregory XIII's eye; in fact he wouldn't even be born for another 900 years or so. Was the demon's last appearance on the day that people at the time would have called Friday the 10th, or does he adjust his date of appearance to conform to the currently extant calendar (in which case he could theoretically be beaten by changing to a 31-month calendar in which every month has only twelve days at most)?
** The family tree seen in "Pardon My Past" states that the sisters' grandmother was born in 1937 and their mother in 1950 - meaning that Penny somehow had a daughter when she was twelve. There's also the episode "Witchstock" which shows a youthful Penny in 1967 (going by the family tree, that makes her thirty, which is okay) - but "That 70s Episode" showed her looking quite elderly in 1975.
** Just narrowly avoided with Leo's past life in the same episode. He's shown to be P. Baxter's lover in the 1920s (or at least Anton pretends to be him) when Leo's birth date is given as 1924. So Leo's past life has to have died and then been reborn pretty quickly. Possible but just barely.
** Paige's birthday is listed wrong on her gravestone in the alternate reality of "Centennial Charmed". The same episode hangs a lampshade on another maths related goof; Cole is retconned into turning a hundred, when a Season 3 episode alludes to him being 115. A demon serving his birthday cake says "I thought you were 117" - and gets blown up for it, implying Cole is sensitive about his age.
** Penny Halliwell's love life gets forgotten about by the writers. She's been engaged six times and married four. Her first husband was the one shown in Woodstock. Despite the many flashbacks to the sisters' childhoods and teen years, there's never any reference or sight of the five other suitors Penny had.
* ''Series/BoyMeetsWorld'' begins in the fall of 1993. Cory is 11 and in 6th grade, his older brother Eric is 15 and in 10th grade, and their little sister Morgan is 5 and in kindergarten. Next year/season, Cory is 12 and in 7th grade, Eric is 16 and in 11th grade, and Morgan is 6 and in 1st grade. So far, so good, right? Not quite. Towards the end of the second season, Cory is suddenly 13 and presumably in 8th grade, considering final exams were taken in a second season episode way before the finale. When the third season begins, Cory and his friends are 14 and in 9th grade, although Eric's aging process is still consistent (17 and in 12th grade). When Morgan suddenly re-appears, she's 8 and in 3rd grade. At the end of the third season, Cory, Shawn, and Topanga end the school year as 15-year-old 10th graders. Eric's age and grade, however, are still consistent (he graduates high school at 18, as he was supposed to). The fourth season begins with Cory, Shawn, and Topanga as 16-year-old 11th graders. Eric is an 18-year-old college reject who's trying to find his place in the world. Morgan's age and grade are ambiguous. The fifth season begins, and the aging process is fluid once again. Cory, Shawn, and Topanga are 17-year-olds in 12th grade, and Eric is a 19-year-old college freshman. Next year/season, Cory, Shawn, Topanga, and (new cast member) Angela are 18-year-old college freshmen, and Eric, Jack, and (new character) Rachel are college sophomores. The year/season after that, however, Eric, Rachel, and Jack are college seniors. Also, at the beginning of the seventh season, Morgan is suddenly thirteen and dating boys.
* ''Series/{{Glee}}'' has an episode ("Acafellas") in the first season where Kurt drives himself, Mercedes, Tina, and Rachel to see Vocal Adrenaline perform. In Ohio, teenagers can get their permit at fifteen and their license at sixteen, and can't drive more than one other person until they're eighteen, which is pretty consistent with most states. Of course, it's possible that Kurt's breaking the law, but given [[SpringtimeForHitler his idea of chaos]]...
** Another episode ("Night of Neglect") has Will Schuester telling the kids they need to sell taffy to raise money. He reasons that, in order to raise $5,000, if each taffy is 25 cents, they need to sell 20,000. He writes it as "5000 x .25 = 20,000." However, one of the producers did later say that the math was intentionally terrible because they thought it would be funny.
** Finn's father apparently died in Operation Desert Storm, when Finn was a baby. However Finn was a sophomore in the 2009-2010 school year meaning Finn was born at the earliest 1993, Desert Storm ended in 1991. It turns out she did lie, as she later reveals Finn's father came back from Desert Storm with PTSD, a drug problem, and an abusive personality. [[FridgeHorror This would be when Finn was conceived]].
** Rachel says in the episode "Dreams" that she was born in December of 1994, meaning when she graduated in Spring of 2012 she would have been 17. Rachel also planned on getting married before graduated without her parent's permission, even though in the state of Ohio (and most others in the country) you need to be 18 to marry without parental consent.
* ''Franchise/PowerRangers'' has screwed up a couple of times. Tommy was seen graduating high school as part of the Class of 1997 at the start of ''Series/PowerRangersTurbo''. By ''Series/PowerRangersDinoThunder'', he's got a [=PhD=], and is a teacher at another high school -- where his students have a prom at the end of the season -- for the Class of 2004. It's impossible to get that qualification, have time to do the research which [[NiceJobBreakingItHero led to the creation of the bad guys]], then become a teacher, in only seven years. Then in ''Series/PowerRangersSamurai'', [[ThoseTwoGuys Bulk]] is shown bringing up teenager Spike, the son of his best friend [[Series/MightyMorphinPowerRangers Skull]]. He's about 14 or 15, which would mean he was born during ''Series/PowerRangersZeo'' or ''Series/PowerRangersTurbo''. Wasn't mentioned at the time!
* In the first episode, of ''Series/YoungBlades'', [[HistoricalDomainCharacter Louis XIV]] is stated to be 15 years old. However, a later episode gives the date as 1652. Since Louis XIV was born on September 5, 1638, he would be either 13 or 14 in 1652.
* ''Series/TheGoldenGirls'' was notoriously bad for this, especially regarding the women's ages. Fanon has tried to gloss over the worst of it by simply saying the women compulsively lied about their ages.
** The worst was regarding Dorothy and her first child. It was repeatedly mentioned that Dorothy had a shotgun wedding at 17, was married for 38 years, and divorced two years before the show began. While all this adds up to her age being fifty-seven with at least one child over 40. However, Dorothy was consistently "in her 50s" during the show's run (at least one time saying she was 55), and neither of her two children were ever shown at being anywhere over 30.
** Rose held together pretty well. In an early episode Dorothy says Rose is 55 and Rose said she was married for 32 years. Since she married at 18, things worked well (born in 1930, married in 1948) until another episode said that her husband had been dead for 15 years, which would have made her 65 when the show began. They were only one digit off (had they said 5 years, it would have worked.) So close, yet so far.
** Blanche was the most consistent, purely by accident. Blanche was obsessively protective of her actual age, so there were very few contradictory ages and birthdates given to the most concrete one. In a flashback, her mother mentioned that she ran off to marry an older man at 17 on Christmas Day 1949. This would mean she started the series at 53, lining up pretty well with an early episode where she begins to experience menopause.
** Sophia says in an early episode that "I've lived 80, 81 years," suggesting she was born in 1906. However, in other episodes, she says she's been walking since 1904 and had romantic trysts between 1914 and 1920, when she would have only been between the ages of 8 and 14. This is usually chalked up to the fact that Sophia had memory problems from a stroke and was possibly senile.
--> '''Sophia:''' I'm 80. I'm supposed to be colorful.
* ''Series/HowIMetYourMother'' had a notable mistake in one episode, where Ted is haggling with a homeless man, trying to buy back some of Marshall's charts after the homeless man took them from the garbage. The homeless man won't accept any price other than a million dollars, so Ted promises him that he'll give him a dollar a day for a million days. The homeless man points out that that's twenty seven thousand years. He added a zero- one million days is actually twenty-seven ''hundred'' years. (This has been corrected on subsequent airings.)
* Averted on ''Series/{{CSINY}}'' where the writers realized that making Christine's brother Mac's Marine buddy would not have worked with her being in her 40s. Mac is about 56 and would have been through basic training in the mid 70s, so she'd have been a small child then. They made him a police partner of Mac's instead.
* In ''Series/TorchwoodMiracleDay'' when the characters are calculating how fast Earth's population is increasing now that [[DeathTakesAHoliday no one can die]], they count the dead people twice.
* Not so a mathematic mistake so much as a slip in research:
** The ''Series/{{Elementary}}'' episode "Solve for X" is about the unsolved [[https://en.wikipedia.org/wiki/P_versus_NP_problem P versus NP problem]] and the real-life million-dollar prize for its solution. A mathematician character correctly exposits that (in a nutshell) P-versus-NP is about whether or not any problem whose solution can be quickly verified by a computer (NP-type problems) can also be quickly solved by one (P-type). A tech CEO correctly explains how it's relevant to cyber-security because encryption involves creating NP-type problems.
** However, both characters imply that "solving" P-versus-NP would result in the ability to quickly solve NP-type problems (thus filling in large swaths of mathematics and ending cyber-security as we know it), which is far from correct. It's possible (in fact, likely) that P and NP are simply not the same set; any mathematician who proved this would still win the million (and some people's relieved thanks). Or maybe P and NP are the same, but proving it would only ''suggest the existence'' of a universal problem-solving algorithm, not necessary create it. Further, even if they found such an algorithm, it only need run in polynomial time. If the time it takes is proportional to the size of the problem raised to the millionth power, it's polynomial time, but no less computationally intractable.
* ''Series/{{Warehouse 13}}'': Claudia is 19 in Season One. It's mentioned that she was 10 when her brother vanished, and that he was missing for twelve years. See the problem here?
* ''Series/{{Justified}}'': Protagonist Raylan's birthdate is given as 1970, yet he supposedly crippled high school baseball rival Dickie Bennett twenty years ago. Assuming that the show takes place during the same year it aired (2011) this would make Raylan twenty-one in high school, which given that he's been a Marshal for nineteen years (requiring him to have a college degree) seems unlikely. ''Justified'' is the name of the series. This is not a JustifiedTrope.
* ''Series/{{Supernatural}}'''s sixth and eighth season premieres both feature one year long {{Time Skip}}s that are frequently not accounted for whenever a date is mentioned on the show.
* ''Series/NickyRickyDickyAndDawn'': In "The Quadfather" (eleventh episode), the four quads were stated to be having their tenth birthday. However, it had been previously stated that they were in fifth grade, meaning they should have been celebrating their eleventh birthday or they should have been in fourth grade. It would be highly doubtful that quadruplets would have all skipped a grade.
* Series/TrailerParkBoys: The episode "Halloween 1977" implies the eponymous main characters are pushing 50 years of age. The actors who portrayed them were all age 34-38 at the time.
* Series/{{Andromeda}} once used the term "nano-millennia" to describe how long the ship's AI was trapped in a box. It was apparently meant to convey a great deal of subjective time based on how fast a computer processes things. However, the prefix nano means one billionth. From that, one "nano-millennium" is only about 31.5 seconds.
* ''{{Series/Merlin}}'' reveals two illegitimate children from Gorlois's wife Vivienne. The first of whom is Morgause, who was smuggled out of Camelot and declared stillborn to be kept secret. The second is [[spoiler:Morgana herself]] and Uther is the father, which poses problems since she and Arthur are roughly the same age -- and Uther either cheated on Igraine while she was pregnant with Arthur or else used magic to conceive Arthur almost immediately after his affair with Vivienne. Morgause was kept secret, which is considerably harder for the ''mother'' to do, and requires her husband to have been away from the kingdom for long enough for Vivienne to have her affair and carry the pregnancy to term. All the while Gorlois was away for long enough not to notice any of this -- and [[spoiler: Morgana's]] conception has to have happened recently enough before his return that the child could be passed off as his.
* A case of Techs Cannot Do Math: A 1963 telecast of ''Series/ThePriceIsRight'' had a contestant, Richard Darling, returning as champ with $10,118 won the week before. At the end of his next show he has won an additional $6,670 in prizes, which would have brought his two-week total to $10,788. The tote screen showed it as $10,778.

[[folder:Mythology and Religion]]
* The people of the northern [[Literature/TheBible Kingdom of Israel]], who were scattered by the Assyrians and disappear from the historical record after that, are popularly known as the "Ten Lost Tribes." The only problem is that the Northern Kingdom consisted of only ''nine'' tribes -- Reuben, Issachar, Zebulun, Dan, Naphtali, Gad, Asher, Ephraim, and Manasseh. The most likely explanation is that somebody subtracted the two tribes of the Southern Kingdom, Judah and Benjamin, from the traditional twelve without realizing that the tribe of Simeon had disappeared from the census at this point; and the priestly tribe of Levi (which by law had no land holdings) was spread out through both kingdoms. The math was always a bit fuzzy anyway, since Ephraim and Manasseh were actually ''half''-tribes (being descended from Joseph's two sons) and the other tribes would sometimes kick Dan off the list for its wickedness (having slaughtered and resettled in a defenseless town in the book of Judges).
* In the Christian Bible, a temple includes a sea (large bowl) of "cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits high. It took a line of thirty cubits to measure around it," implying that pi is equal to 3 and not 3.14159. However, the sea is also mentioned as being a "handbreadth" thick. Taking the thickness of the sea into account, [[http://www.purplemath.com/modules/bibleval.htm the numbers match quite accurately.]]

* The song/story "A Billion Baseballs" by the Green Chili Jam Band does multiple calculations related to these baseballs and gets almost all of them wrong. For example, it says that this many baseballs placed on the ground would take up a giant square "eighty miles around." Since baseballs are three-inch diameter objects, a square of 31,623 by 31,623 baseballs would have a perimeter of under six miles.
* Foxy Brown's verse on The Firm's "Affirmative Action" contains this horrible bit of addition:
-->We gotta flee to Panama, but wait it's half-and-half\\
Keys is one and two-fifth, so how we flip\\
Thirty-two grams raw, chop it in half, get sixteen, double it times three\\
We got forty-eight, which mean a whole lot of cream\\
Divide the profit by four, subtract it by eight\\
We back to sixteen, now add the other two that 'Mega bringin' through\\
So let's see, if we flip this other key\\
Then that's more for me, mad coke and mad leak\\
Plus a five hundred, cut in half is two-fifty\\
Now triple that times three, we got three-quarters of another ki
* The Shooter Jennings concept album "Black Ribbons" is set in a not-too-distant future dystopia. The narrator, the Will 'o the Wisp, makes reference to a real book published in the 1970s, stating it was written forty years ago, putting the date around 2010, when the album was released. This could be a case of a changed past, but then he mentions Obama's election and says everything went to seed after that. Either Obama's term was cut short, or the math is wonky. This is made worse by the fact that Creator/StephenKing wrote the narration.
* The Music/RageAgainstTheMachine track "Down Rodeo" includes the classic hook: ''So now I'm rollin down Rodeo with a shotgun / These people ain't seen a brown-skinned man / since their grandparents bought one.'' Even if the song is describing a 1960s Black Panther, which the lyrics seem to suggest, that's over a century since the end of slavery, making it extremely unlikely that anyone there would have been old enough to see one purchased. That lyric is obviously not meant to be taken literally.
* "The Doctor's Wife" by TheClockworkQuartet magnificently details an ApocalypticLog by a doctor obsessed with curing his wife of a serious illness. The only trouble is, the dates at the beginning of each verse conform to no known calendar.
* In the Vietnam War protest song "I Was Only 19" by Redgum is the line ''And Frankie kicked a mine the day that mankind kicked the moon / God help him, he was going home in June'' which implies that Frankie was about to go home when he was killed by a mine. But the moon landing didn't happen until July - which would mean Frankie still had almost an entire year of service to go.

[[folder:Newspaper Comics]]
* The ''ComicStrip/DickTracy'' story "The Man of a Million Faces" features a string of bank robberies committed by celebrity lookalikes -- or is it a single master of disguise? The story makes a big deal of using known heights of objects to measure (they mean "calculate") the perpetrator's height, which turns out to be a consistent 5'11". Yet a previous diagram shows a line labeled 69.9" going over his head with room to spare.
** Another ''Dick Tracy'' story involves thieves stealing small-valued coins from parking meters. Now, $2 in nickels is only 40 coins, far less than the large handful shown, whereas when Larry throws $20 in pennies onto his mother's stomach, the size of the bag pictured is about right, but that would ''seriously'' hurt.

[[folder:Tabletop Games]]
* In the ''TabletopGame/{{Warhammer}}'' setting, different factions use different calendars, which contain references to the standard Imperial Calendar to allow for calibration by sufficiently interested fans. Unfortunately, when the same events are compared in different calendars, the dates are all out by one year, as the writers forgot that the first year of a reign starting in, say, 2000, is 2000, not 2001.
** In the current Codex for the Black Templars space marine chapter in ''TabletopGame/{{Warhammer 40000}}'', the introduction states that the whole chapter is divided into "crusades", of which there are "usually no more than a few", comprising fifty to several hundred marines. This would be fine if the Templars were a chapter of one thousand, following the Codex Astartes, but the same page -- nay, the same paragraph -- says that there are between five and six thousand Templar marines. The numbers just can't work with only a "few" crusades, unless a "few" is pretty large or each is over a thousand strong.
** It does work out if you interpret "crusades" as meaning "in active combat". There could be any number of Templar companies doing routine garrison duties or recruitment.
** And after the Horus Heresy, the ten remaining Space Marine Legions were split into a thousand chapters, so each Legion would (on average) be split into a hundred chapters. In the same book, the Ultramarines Legion is claimed to have by far the most offsplit chapters, at ''twenty-three''.
*** Post Horus Heresy there were actually nine remaining legions, and the thousand chapters is both an approximation, and valid for "current" time in the 40k universe (M41), not immediately post Horus Heresy (M31). There have been loads and loads of foundings of new chapters in the intervening 10,000 years.
*** This is backed by Codex Grey Knights as the other chapters noted its oddness as to their number (666) despite only a few hundred chapters having been founded.
*** Plus although the legions had a theoretical strength of 100,000 very few of them were actually up to full strength, especially after taking heavy casualties during the Heresy itself. Additionally the list of Second Founding chapters is not complete, many of the chapters have been destroyed and their name lost to history.
** Space Marine chapters, famously, are composed of a thousand marines each (not counting casualties). Which makes sense -- there's ten battle companies, each composed of ten squads of ten men each, for a thousand marines... plus the captains/chaplains/command squads (7 per company, or an additional 70 marines), the Chapter command (roughly 15 marines, counting the honour guard), the armoury, the apothecarion, the librarius (cumulatively another 70 marines), plus the vehicle crew, starship commanders, and pilots. In all, "a thousand" marines, is actually at least 1350 and could potentially be upwards of 1600.
** The ''TabletopGame/RogueTrader'' RPG's writers apparently forgot about the square-cube law when giving the size and weight of the starships. The smallest vessels are slightly denser than balsa wood, while cruisers and battlecruisers have roughly the density of smoke.
** The explosives in the Inquisitor Handbook of ''TabletopGame/DarkHeresy'' have some... weird blast radius. Promethium, especially, is ridiculously volatile. During a session, supertanker filled with five hundred millions liters of promethium (that is surely a lot, but, again, this capacity falls easily in the modern super tankers range) blew up. The player asked the Game Master if they were safe at the other side of the harbor, so he made a couple of counts to find it out: imagine the hilarity when they found out that, according to the manual, the resulting explosion had a radius of 1.6 millions kilometers (almost a million miles). To give an idea of the scale, the fireball is about twelve times the size of the sun. Somebody should inform the High Lords Of Terra that the conventional Exterminatus methodologies are largely outdated: why waste an expansive cyclonic torpedo when you can go supernova with a simple ship filled with cheap promethium?
* For the "Ace In The Hole" miniadventure included with the ''Star Ace'' GM screen, the [=PCs=] are supposed to rob a casino blind as revenge for the casino owner putting a bounty on one of your [=NPC=] buddies. You're also supposed to leave 5000 chips (game currency equivalent to $5 million US) behind to cover the gambling debt that started this whole mess. The scenario uses random rolls to determine just how much money is in the casino at any given point, but if you assume maximum rolls there's only 700 chips in the whole joint. You can't even make up the other 4300 chips by robbing the 1d10x100 customers, because all gambling is done with house scrip instead of coins. Also, the casino owners have put a 1000 chip bounty out on that [=NPC's=] head. It's fairly simple for the [=PCs=] to bluff their into the casino office by producing fake evidence that they'd just earned the bounty... which the casino owner isn't able to pay because he doesn't have that sort of cash on hand. The ''Star Ace'' game assumes that all currency is "hard" currency; computer credits and the like aren't used.
* In one edition of ''TabletopGame/WarhammerFantasyRoleplay'', it attempts to make the point that magic users are rare by claiming 1 in 1,000 people have some magic ability, 1 in 1,000 of those are true wizards, and out of ''those'', only 1 in 10,000 are cut out to be battle mages. That means a planet with the population of ''modern'' Earth would probably have ''one'' at most. It seems unlikely a medieval setting would have even that many.
* Speaking of which, using the completely bonkers equations given in ''TabletopGame/RoleMaster'''s first companion to determine one's character's height, weight, bust size, waist size and shoe size (you know, in case you're a very, very anal GM and your dungeon has Boots of Speed in size seven -- this is RoleMaster, after all, the ''VideoGame/DwarfFortress'' of pen and paper [=RPG=]s) you would always end up with a monster who had feet twice as long as his waist or somesuch.
** Likewise, the original 1st Edition AD&D tables for character height and weight failed to link these two characteristics, meaning the shorter your PC was, the fatter they were, and tall characters were built like string beans, if not dental floss. Furthermore, the weight tables for demihumans were way, way too extreme, meaning your dwarf hero could've had the approximate density of osmium.
* ''TabletopGame/DungeonsAndDragons'':
** Several ways to hypothetically gain infinite currency involve buying items and selling their parts for more than the initial item was worth. For example, in 3.5E a 10ft ladder could be purchased for 5 copper pieces, split into two 10ft poles, then sold for 1 silver piece per pole.
** In the game ''In The Labyrinth'', a full wineskin costs $2, while an empty one costs $3. Bottoms up!
** The numbers for the fireball spell were a little off. The shape was controlled by the caster and the volume was fixed, and the resulting blast tended to be the size of Pennsylvania.
** Old-school [=D&D=] generally had horrible math. The way "create food and water" spells scaled, a high level cleric could easily clear a dungeon by flooding it with water, since he would create tens of cubic meters per cast.
** In the [=D&D=] world, pi is apparently 4, given how radius of spells like fireball is determined in squares. [[DiagonalSpeedBoost And diagonal movement is the same as horizontal, so sqrt(2) = 1.]] Math in Greyhawk must be really, really screwy. It's a bit better in version 3.5, where sqrt(2) = 1.5. As later editions starting with third at the latest emphasized miniatures tabletop play more and more over the more abstract "theater of the mind" style[[note]]that's a fancy way of saying "everything just happens in the players' and DM's shared imagination"[[/note]], eventually ''something'' had to give, and the already somewhat spurious notion of tracking imaginary movement and the various geometries of assorted similarly imaginary effects with {{ludicrous precision}} was it.
** A potion has no appreciable weigh, neither does acid, holy water or [[GreekFire alchemist's fire]]. But a potion vial (the sort of thing that they are in) does. Therefore liquids in [=D&D=] have negative weight.
** A case where it was applied to the mechanics underpinning an entire class: the difficulty a truenamer must beat to use their powers goes up ''at least'' twice as quickly as their actual rank in the Truename skill does -- it goes up by 2 per hit die of the target opponent, hit dice are usually equivalent to levels when calculating encounter difficulty but can be higher, and the truenamer can only add one rank of the Truename skill per level. Meaning that by level 20, a truenamer needs to make up a deficit of twenty skill ranks with magic items and stat increases (in other words, +5 to the key stat for levelling up, +5 to that stat from a really expensive magic item, and then another magic item granting Truename +15) to have the ''same chance'' of their power working on a level 20 monster as a level 1 truenamer would when targeting a 1 HD monster. And then, when they do use a power successfully, the difficulty goes up. There's a reason optimisers tend to dismiss the truenamer as utterly useless.
** To join the Fists of Hextor in the early 3E splatbook Sword and Fist, you have to kill a member of that organization. Apparently membership numbers of that organization can only decline. (The Sith have a similar problem)
* Some of the early ''Franchise/{{Star Wars|Expanded Universe}}'' tabletop RPG material, namely the Imperial Sourcebook, refers in much detail to the Order of Battle for starships. One of these configurations is called a Fleet Bombard, which would include two System Bombards, which in turn include three Bombard Squadrons, which in turn would include two Torpedo Lines, which each usually consisting of two Torpedo Spheres. That means a single Fleet Bombard should have about 24 Torpedo Spheres. Later in the book, however, they talk about how there are only six Torpedo Spheres in operation in the entire fleet.
* Considering the giant pile of bile that is ''TabletopGame/{{FATAL}}'', it should be no surprise that randomly generated body parts can have negative proportions. There's the particular case of the success rolls. First you roll percentile dice to find the number to roll against then roll for success to see if you get a higher number. Someone must have though the extra roll would add randomness. The result is that the odds are always 50.5%.
* In ''TabletopGame/WerewolfTheApocalypse'', when a Garou and their kinfolk partner conceive, the likelihood that they will produce a Garou child is only 10%, compared to a 90% likelihood that they will produce a kinfolk child. That means that ''each'' Garou-kinfolk couple would have to have ''at least'' ten children to keep the Garou population stable!
** In universe there is a lot of discussion about watching over kinfolk communities is a major duty of the tribes. This implies that the majority of Garou are born to kinfolk couples rather than Garou parents. The math still implies a much larger kinfolk population that the fluff supports, but the Garou population isn't supposed to be kept stable by direct siring.
* In ''TabletopGames/IronKingdoms'', casualty figures for Cygnar indicate that its entire population has been wiped out. Twice. Most nations only manage it once.
* ''TabletopGame/BattleTech'' has mostly avoided this trope due to placing a moratorium on providing hard numbers on things like the energy output of lasers but it still has some issues. For example, the Avalon class Warship's stated dimensions are large enough that assuming its armor has the density of steel, it would have to be the thickness of a Mylar balloon.

* ''Theatre/ThePhantomOfTheOpera'' takes place in 1881. Its sequel, ''Theatre/LoveNeverDies'', takes place ten years later, in 1907. ''Phantom'' itself has had its share of chronology issues -- the dates of the prologue, the principal action, and the death of Christine's father have shifted several times since the show's inception, and trying to reconcile all three dates with each other has resulted in headaches for many a phan. A brief discussion on the subject can be found [[http://www.phantomoftheopera.com/modules/article/view.article.php/c6/11 here]].
* ''Theatre/ThePajamaGame'' has a song named "Seven and a Half Cents" involving the singers detailing what they could buy with that raise over a given number of years. For the last figure for ten years, they forget to carry when multiplying, resulting in the wrong answer.
* The stage version of ''Film/{{Hairspray}}'' starts on a Monday in "early June", 1961. It ends on June 6th, 1961. However, around 10 days pass between the beginning and ending scenes. This problem is compounded by the fact that the first Monday in June, 1961, was the 4th.
* In ''Theatre/FiddlerOnTheRoof'' after a TimeSkip, Tevye says Tzeitel and Motel have been married for two months. A scene or two later (with no time skip), they have a baby. Either Tzeitel had the world's shortest pregnancy or she somehow had no full belly when she was seven months pregnant at her wedding.
* ''Theatre/CharlieAndTheChocolateFactory'' falls afoul of this in Act One with regards to Veruca Salt finding her Golden Ticket. In the IAmSong "When Veruca Says" her father claims that his workers were "shelling" Wonka Bars "for forty days and forty nights", but the contest was only announced the previous day. (Granted, it might have ''felt'' that way since they're dealing with [[SpoiledBrat Veruca Salt]] here.) This might be a matter of the book and the lyrics being penned by different writers.

[[folder:Video Games]]
* ''Franchise/{{Halo}}'':
** According to ''Literature/HaloTheFallOfReach'', 33 [[SuperSoldier Spartan-IIs]] survive the augmentation process in the year 2525, of which 28 survive to 2552, of which 25 were available for Operation: RED FLAG. However, the numbers in media released since ''[=TFoR=]'' don't add up to this at all: Three Spartans go MIA in ''VideoGame/HaloWars'', two more are revealed to have been MIA in ''Literature/HaloGhostsOfOnyx'', seven die in ''Anime/HaloLegends'', two more die in [[AllThereInTheManual supplementary material]], and three of the supposed 25 [[ComicBook/TheHaloGraphicNovel were]] [[Literature/HaloGlasslands deployed]] [[VideoGame/HaloReach elsewhere]] during the preparations for RED FLAG. This means there only could have been 13 Spartans available for RED FLAG in 2552. This took ten years to be rectified, until "[[VideoGame/HaloReach Dr. Halsey's journal]]" (co-written by ''[=TFoR=]''[='s=] author) revealed that the gaps (and then some) were filled by [[NotQuiteDead secretly resuscitated Spartans]] (not part of the original 33 graduated ones) who were presumed dead or crippled in augmentations. This allows for up to 37 "washouts" to have also become Spartan-[=IIs=] by 2552; the protagonists of ''ComicBook/HaloBloodLine'' are implied to be among this number, and Red Team (the ''Halo Wars'' Spartans) were outright confirmed to be so in ''VideoGame/HaloWars2''.
** Dr. Halsey's journal, included with the special editions of ''VideoGame/HaloReach'', has some confusion with Halsey's pregnancy. It's implied she became pregnant on November 17 2524, but her daughter Miranda was born on February 28th 2525. In other words, Halsey's pregnancy apparently only lasted three months?
* In ''VideoGame/KirbySuperStar'' and its remake, there's a sub game called "Megaton Punch" which has Kirby compete with several other characters in a planet cracking contest. During the game, if Kirby gets a perfect strike like [[https://www.youtube.com/watch?v=5lxNNlQYttU like shown here,]], the game states the force is... 201 MT. Now 201 MT may seem like a big number, but in actuality, that would only be enough force to level a city on Earth. Now even if one assumed that Popstar is more fragile than Earth, the level select map in ''VideoGame/Kirby64TheCrystalShards'' shows an Earth-Esque planet of similar size to Popstar. And since it just so happens that it requires over '''''50 QUADRILLION''''' megatons (>50,000,000,000,000,000, on paper) to bust the Earth, saying HAL's token number is too low would be an '''understatement'''.
* In ''VideoGame/PokemonRubyAndSapphire'', the Pokemon "Wailord", the largest Pokemon in the game, has a weight that doesn't seem to match it: Wailord is 14 metres high, and weighs 398 kilograms. Both these numbers are ''big'', but it's weight isn't ''nearly'' as high as it should be. As it's official description states, it's roughly the height of a 5 storey building, but seeing as [[https://en.wikipedia.org/wiki/Human_body_weight the average human weighs 62 kg,]] it weighs less than a group of 7 people. Actual whales are smaller yet weigh ''at least'' a few tonnes.
** This may be intentional, Wailord is based on a blimp and as such has high HP and low defense so it would make sense that his weight is far smaller than his size, he's a baloon.
* In ''VideoGame/DeusEx'':
** One ([[TakeYourTime supposedly]]) timed event gives you 24 hours to live. A helicopter takes you from one location (Liberty Island) to another (Hong Kong) in a trip that is based on context to be less than eleven hours (23 hours left before the flight, twelve hours have passed a decent amount of time after it). Google Maps gives the distance between the two at 8,047 miles, and the max speed ever recorded on a helicopter was 249.1 mph. To make the trip the helicopter in question would need to go over 730 MPH (almost three times the record) without stopping.[[note]]In the real world opinions are divided on whether this would actually be physically possible, even given superior materials like Deus Ex nanotech; if it is, the helicopter wouldn't look anything like the relatively-conventional Dibbuk.[[/note]]
** There are so many Writers Cannot Do Math moments with dates in Deus Ex that it's difficult to tell when it's supposed to be. Guesses have ranged between 2045-2065. 2052 does seem to be the most consistent, however, and is the one used by the sequel.
* ''VideoGame/JakXCombatRacing'' confirms that [[TheHero Jak]] and [[WrenchWench Keira]] are only one year apart in age. So, [[spoiler: young Jak would have had to be at most one year old when he and young Samos went back in time. However, Baron Praxis was in charge of Haven City for at least two years, so Jak would have to have been at least that old by the time he went back in time]]. A common fan theory was that Keira was adopted, but that was debunked once Samos mentioned that she was "just like her mother." The new theory is that Keira's mother was single and married Samos. If she is indeed Samos's biological daughter, as the series seems to treat her, then it falls under this trope.
* In ''Franchise/TheSims 2'' & ''3'', there are a lot of these. For example:
** ''The Sims 2'' & ''3'' made Michael Bachelor into Bella Goth's older brother, but in the first game she already had a child, while he was just out of college. And the Sims 3 was supposed to be about 25 years before the first game, yet Michael is a 20-year-old man.
** Dina Caliente in the second game has a memory of having her first kiss with Michael Bachelor, despite the fact that she married him when he was an elder, which would mean her first kiss was with a middle aged man.
** Mortimer and Cassandra's memories say that she was almost, but not yet, a teen when Alexander was born, and therefore only twelve years older than him. But if she's a kid in [=TS1=] and there's 25 years between the two games, she must be pressing thirty by [=TS2=], and Alexander should at least be in his late teens, not a child as he's presented.
** Kaylynn Langerak shows up in [=TS3=] as a child about the same age as Mortimer Goth. There's fifty years between [=TS3=] and [=TS2=], and Mortimer is fittingly an elder by that time. So why is Kaylynn barely into adulthood?
** Brandi Broke starts [=TS2=] pregnant with her third child by her late husband, who has her husbands genetics and is recognized by the game as his. Yet her husband died before her second child was born, meaning he somehow sired the third one after he died. In-game, the third child isn't actually his son. The baby is always a boy because Brandi is pregnant with herself, and a character who is pregnant with themselves always has an opposite-sex child.
* Sierra's ''VideoGame/PoliceQuest'' has a very confused time line. The game was made in 1987 and is apparently supposed to take place in 1983, but there are some references to 1986, such as Hoffman's gun, which was reported stolen three years after his arrest. ''Police Quest 2'' then makes this worse by taking place one year after the original, but mostly seems to refer to 1987 (although there are a few references to 1984 in there). Then in ''Police Quest 3'', the computer records indicate Sonny Bonds was hired by the LPD in 1985, which is ''after'' the date that ''Police Quest 1'' was supposed to take place, and is even weirder considering that in ''Police Quest 1'', it was stated that Sonny was already a fifteen year veteran on the force!
* ''VideoGame/TeamFortress2'':
** Various items and upgrades in Mann Vs. Machine have descriptions saying it does an action (attacking, switching weapons, revving up a minigun) some % faster or slower, which means the time it takes to complete that action should be divided by the sum or difference of 1 and a hundredth of that percentage (for example "50% speed increase" would mean dividing the time by 1.5, "20% speed decrease" would mean dividing the time by .8). However, those numbers are instead what percentage of the original time the difference in time is (so "50% speed increase" means multiplying the original time by .5 and "20% speed decrease" means multiplying the original time by 1.2). The confusion comes from describing a change in time (as the numbers show) as a change in speed (as the terminology suggests); speed is related to time, of course, but inversely, hence the need for division. Basically the math is correct, but it should have said "50% less time" rather than "50% faster," which makes this instead a possible case of..."Can't Speak Their Own Language"?
** The Heavy's [[MemeticMutation famous line]] in [[http://www.teamfortress.com/classes.php?class=heavy#movie "Meet The Heavy"]] that his gun "fires two hundred dollar, custom-tooled cartridges at 10,000 rounds per minute," so firing it for 12 seconds costs $400,000. This isn't wrong in itself; but in-game, the gun fires 4 bullets every one-tenth of a second, or 2,400 rounds per minute. The $200 bullet cost is referenced in-game by the Scout, so it seems that firing the gun for 12 seconds costs a mere $96,000. And then the achievement for firing $200,000 worth of ammo in one life is even slower: it counts each ammo expenditure spent as costing $200 (even though the gun shoots four bullets for each), meaning 12 seconds of firing only costs $24,000.
* The Time of Troubles in the ''TabletopGame/ForgottenRealms'' setting for ''TabletopGame/DungeonsAndDragons'' caused dating issues for a couple of games based on the setting.
** The ''Franchise/BaldursGate'' series is centered around the story of the mortal children of the god Bhaal, who foresaw his own death during the coming Time of Troubles and produced a number of mortal children to ensure his resurrection through them. In the last installment, ''Throne of Bhaal'', you learn that an important Bhaalspawn character, who is known to be about twenty-one at this time, was being held as a baby by a cult of Bhaal worshippers who intended to sacrifice Bhaalspawn children to raise Bhaal or something. This all makes perfect sense until you remember that the Time of Troubles was given as having been about a decade ago. This means that the cult was operating about ten years ''before'' Bhaal died, which makes its actions nonsensical or at least unexplained.
** Funnily enough, the first ''VideoGame/BaldursGate'' game acknowledged this trope exists, in your journal entry for completing the side quest "A Rogue Ogre".
---> "One dead ogre equals 95 gold pieces. Unshey claims to be a writer, but it sure is hard to argue with her math."
** A similar PlotHole pops up in ''VideoGame/NeverwinterNights2: Mask of the Betrayer'', where part of Myrkul's plan in creating the Spirit-Eater Curse was [[spoiler:to ensure his immortality by abusing the ''TabletopGame/ForgottenRealms[='=]'' GodsNeedPrayerBadly rule (i.e. as long as there's a Spirit-Eater, there's always going to be someone who believes in him, thus he can't truly die)]]. However, [[spoiler:the heretic whom he punished by turning into the Spirit-Eater]] is said in-game to have rebelled hundreds of years ago. Again, the Time of Troubles, after which GodsNeedPrayerBadly was established by the Overgod Ao, took place in 1358, and the game takes place in 1374.
* Two examples in ''VideoGame/NoMoreHeroes2DesperateStruggle'':
** After becoming ranked 23rd in the UAA, Travis is told by Sylvia about a battle royale between him and ten other assassins, and if he wins by killing them all, he will be 10th. But if ten opponents face him, then he should remain in 13th at most. Granted, when he arrives the battlefield, [[spoiler:Dr. Letz Shake]] gets rid of all of the opponents so Travis only has to fight him; but even if he was the one ranked 10th, positions 11th and 12th are still empty.
** After becoming ranked 7th in the UUA, Travis's brother Henry awakens from his coma and reveals via a telephone message that he had already beaten three more assassins for him. As a result, Travis's ranking drops to ''5th'', instead of 4th. The only way this can make sense is if one of those fights was a Rank Defense match similar to the fight with Kimmy Howell, but it's never stated in any way.
* The intro to the ''VideoGame/{{X}}-Encyclopedia'' says that it is designed to set the canon in stone. It does that for the most part but introduces a couple new problems. For example, page B-29 says that the [[RingworldPlanet Torus Aeternal]] was blown up in February 2948, then ''the next gorram page'' says the gate network shut down in December '''2947'''. So either the Argon Fleet can teleport, or somebody got a date wrong. Couple that with, ''X3: Albion Prelude'' takes place ''after'' the Torus went up, and the date in-game is ''2949'' after you convert from the Argons' AlternateCalendar. [[SciFiWritersHaveNoSenseOfScale And let's not even begin discussing about the other colossal absurdities in mathematics that plague the rest of the series's aspects...]]
* According to the manual for the medieval simulation game ''Lords of the Realm'', the designers meant for flocks of sheep to grow in size more rapidly than herds of cattle, even though cattle calve every season and sheep only lamb in the Spring. And, indeed, assuming sufficient pasture land and adequate herdsmen for both, a flock of 100 sheep will produce more lambs in the Spring than a herd of 100 cattle will produce that same Spring. Unfortunately, either the manual writers or the programmers or both failed to understand the concept of compound interest. By analogy, which bond would you rather hold: the one according to which you are owed a principal of $100 plus 5% interest, compounded yearly, or the same principal plus 3% interest, compounded quarterly?[[note]]Hint: the latter will be worth $106.09 after only two seasons.[[/note]] Of course, what that meant is that your herds of cattle would tend to grow much faster than your flocks of sheep, which meant that you would tend to devote more of your finite pasture land to cattle than to sheep, which would in turn tend to make your herds grow faster still relative to your flocks....
* Colton from ''VideoGame/{{GUN}}'' is an adult. According to characters his adopted father was nearly died in the Civil War, afterwards he found Colt. With all the information Colton cannot be older than twelve but he's obviously an adult. To make matters worse he says twelve years ago he was attacked by a cougar, and he's clearly still the same age in the flashback.
* Trying to determine the age of Big Boss from ''Franchise/MetalGear'' is a bit of a nightmare thanks to [[SeriesContinuityError inconsistent dates and ages]]. ''VideoGame/MetalGearSolidPeaceWalker'' in particular has one character, as he's threatening to kill Big Boss, claim he will be "dead at 39, just like [[UsefulNotes/CheGuevara El Che]]". This would place him as being born in 1935, which is a problem because Big Boss was previously established as being a Korean War veteran ''and'' in the Green Berets before The Boss took him under her wing (even if he lied about his age to enlist, that wouldn't work for a special forces unit). Before that came commentary and promotional material for ''VideoGame/MetalGearSolid3SnakeEater'', which established him as being in his 30s in 1964, which would be a bit more believable -- except it was ''also'' stated early in ''VideoGame/{{Metal Gear Solid 2|SonsOfLiberty}}'' that he was in his late fifties when [[CloningBlues the Les Enfantes Terribles project]] was underway, which was in 1972, just eight years after ''[=MGS3=]''.
* In ''VideoGame/AVeryLongRopeToTheTopOfTheSky'', the God's Eye can be clearly seen to have nine saecelium crystals. After [[spoiler:Raccoon]] takes one crystal, [[spoiler:Rutger]] is left with... seven, somehow. (This is fixed in the Major Update.)
* The ''VideoGame/{{Warcraft}}'' franchise has had some awkward moments in its timeline, even ignoring intentional {{RetCon}}s.
** The Worgen began as humans from the nation of Gilneas, who sealed themselves behind a great wall after the Second War. The Worgen curse spread sometime after that point, and their isolationism wasn't broken until the Greymane Wall was shattered by the Cataclysm. Somehow, despite this happening in less than a year, the Worgen can be found all over the world in Cataclysm's new questing experience, often times with roles that imply they've had a long history.
** The questline involving the Worgen Fiona and her friends in Eastern Plaguelands does this with more than just the Worgen.
*** The relationship between Fiona and her companions (using such phrases as "her boys") imply a long term surrogate family relationship, but the Worgen hadn't been outside of their home for even a year at the time. Similarly, Tarenar, the elf, reminisces about killing zombies in his homeland as a kid while Gidwin, the dwarf, reminisces about the Argent Crusade inspiring his childhood as a paladin, despite the first thing not being able to have happened more than eight years ago, and the latter ''one'' year ago. While it's possible that they're young enough to pretend those things were old to sound older and more mature, it doesn't explain everything.
*** Argus Highbeacon is assumed to have been in the Argent Crusade for a long time due to his age, despite the Argent Crusade only being formed the previous year. This is taken to the extreme in the quest "Argent Call: The Trial of the Crypt". Maxwell Tyrosus says that joining the Argent Crusade is joining a family with a long line of fallen ancestors. Even if you count its predecessor, the Argent Dawn, you're still talking about something formed some time within the last eight years. Managing to make it even worse, the trial is carried out by the ghost of Lord Raymond George, one of said ancestors, and explicitly said to be Maxwell's predecessor. Considering Maxwell was a ''founding member'' of the Argent Dawn, it's impossible for Raymond to have come before him, let alone any sort of long line before ''that''.
* In ''[[FireEmblemTellius Fire Emblem: Radiant Dawn]]'', we hear a bit of exposition regarding a ruler who was cursed. Said curse killed one of his subjects, then the next day killed two subjects, the next day three, and so on. It is said that the curse was lifted on the one hundredth day, and that by this time half the ruler's subjects had fallen to the curse. One hundred days of such a curse would kill 5050 people, so if this is accurate then the kingdom of [[spoiler:Kilvas]] had somewhere around 10100 citizens at the time - which is a preposterously low number for the population of a country.
** To hammer it home, at one point in the dialogue it's mentioned that 10000 soldiers are guarding a fortress, and that this is very low, showing that one nation having 10000 citizens in its ''military alone'' is preposterously low.

[[folder:Visual Novels]]
* ''VisualNovel/{{Narcissu}}'' and its sequel, ''Narcissu ~ Side 2nd'', have trouble keeping Setsumi's age straight. In ''Side 2nd'' (which takes place during the summer of 1999), Setsumi is referred to as being an Aquaries (thus born in late January or February), and it is alternatively claimed that she is fifteen years old, or that it is her fifteenth summer (which would make her fourteen). The original game (taking place in late January and early February of 2005), claim that she is 22, but adding the years up from her claimed age in ''Side 2nd'' indicate that she should be within a month of either her 20th or 21st birthday, depending on whether one uses the "15th Summer" claim or the "15 years old" claim. Also, in the prologue of ''Side 2nd'' (which takes place between the two stories), Setsumi makes a remark about how she's been hospitalized on and off for a decade. The main story indicates that she was first hospitalized sometime in April 1997, thus making it impossible for the claim of a decade to be correct.
* In ''VisualNovel/HigurashiWhenTheyCry'', Hinamizawa has a population of roughly 2000, yet there are only 20 pupils in the village's only school. Realistically, around one ''tenth'' of a population would be of school age. (The TIPS say that half the children in the village go to school in Okinomiya instead, which helps a little, but isn't nearly enough.)
* Early into ''VisualNovel/SuperDanganRonpa2'', Monokuma reveals that [[spoiler: the students lost two years of their memories]]. If one however factors in all the cumulative time periods, it actually more than likely twice that number.
* Some times in ''Franchise/AceAttorney'' don't match.
** In last case of ''Trials and Tribulations'' it is stated that Phoenix dated "Dollie" for 6 months, when it was actually almost 8 months[[labelnote:Note]]From August 27th to April 11th following year[[/labelnote]].
** Phoenix is 26 in ''Trials and Tribulations'' and 33 in ''Apollo Justice''. Shadi Enigmar's case happened in backstory of ''AJ'', 7 years prior to game events, which would place it on the same year as ''T&T''. Enigmar's case happened in April, so it would have to happen before the T&T cases, earliest of which(excluding flashback cases) happens in October, but that's not possible because [[spoiler: Enigmar's case resulted in Phoenix's disbarment]]
* ''VisualNovel/ZeroTimeDilemma'' deals with lot of science and math, both basic and advanced (mostly done by [[BrainyBrunette Akane]]), and most of the time gets it right, but one mistake managed to slip in. At one point Akane says that probability of getting 3 ones by throwing three dice at once is 1/216 (which is correct) but attempting it three times would give 1/72 chance, which is close but not entirely correct. Probability of getting at least one success with three attempts is 1 minus probability of failing three times in a row, in this case it's 1-(215/216)^3 or more precisely 139321/10077696 which is slighly lower than 1/72.

[[folder:Web Comics]]
* Averted in ''Webcomic/SchlockMercenary'' [[http://www.schlockmercenary.com/2005-06-04 here]]. The author even accounted for the equal amount of regular matter that would be converted to energy when taking 320 milligrams of anti-matter and converting to the equivalent explosion powered by TNT. ([[http://www.wolframalpha.com/input/?i=13.75+kilotons+of+TNT Quick link to the maths]]). Schlock's [[ViewersAreGeniuses readers]] can do math as well: the writer infamously challenged them to, given a few distantly-related numbers, calculate the height of the "Hellavator" lunar space elevator, only for several readers to send in accurate calculations and numbers, and show their work.
--->[[http://www.schlockmercenary.com/2001-01-23 Schlock fans get an A+. You are all far, far smarter than I gave you credit for.]]

[[folder:Web Original]]
* ''WebAnimation/HomestarRunner'': In Coach Z's music video "Rap Song", a featured guest singer proclaims, "[[InCaseYouForgotWhoWroteIt My name is Tenerence Love]], plus [[RunningGag my name is Tenerence Love]], divided by [[RuleOfThree my name is Tenerence Love]], equals [[OverlyLongGag my name is Tenerence Love]]...remainder 3." Depending on how the operations are grouped, the value of "[[TitleDrop my name is Tenerence Love]]" could be -1[[note]](x+x)/x = 2x/x = 2 = x+3[[/note]] or it could not exist at all[[note]]x+(x/x) = x+1 = x+3[[/note]]. [[note]]Of course, RuleOfFunny kicks in to defend the Chaps.[[/note]] If we let "my name is Tenerence Love"=x, we have (x+x)/x=2=x+(3/x), since "remainder 3" means the undivided portion of the fraction. Rearranging, we get the statement x^2-2x+3=0, and by using the quadratic equation we find the value of "my name is Tenerence Love"=1+sqrt(2)i or 1-sqrt(2)i.[[note]]But then again, each of us has an imaginary part...[[/note]]
* The ''{{Creepypasta}}'' story ''The Russian Sleep Experiment'' starts out with five Nazi prisoners and has three by the time they leave the facility, yet still manages to include death scenes for four or five after that.
* WebVideo/TheNostalgiaCritic, in his ''Film/EndOfDays'' review, as part of a long string of math equations, infamously uttered that "9+9+9=21". That's about as basic of mathematics as one can get and [[TheDitz he screwed it up]]. He later apologized for it in one of his "Fuck ups" specials.
* ''LetsPlay/MarioPartyTV'': One comment pointed out that Steeler miscalculated the odds during the Pagoda Peak playthrough. The probability of rolling 4 of the same number is not 1/10,000. Since the dice blocks are numbered one to five, and there are 5 possible ways to get all 4 numbers being the same, the probability ends up being: 5/(5^4) = 1/125 (about the same as a golden with 1-10 blocks)

[[folder:Western Animation]]
* ''WesternAnimation/AvatarTheLastAirbender'':
** In season 2, Azulon was said to have ruled for 23 years, making Ozai the Fire Lord for the last 6-7 years of the war, and Sozin for the first 70 years and possibly before. Then, during the third season, the website states that Sozin died at the age of 102, even though he's clearly older than 32 when he starts the war in "The Avatar and the Fire Lord". WordOfGod then stated that [[RetCon Sozin ruled for the first 20 years of the war, Azulon the next 75 years, and Ozai the last 5]].
** The ''other'' side of the Fire Nation Royal Family doesn't have enough generations to have possibly spanned the 100 year war: Roku, the Avatar before Aang, turns out to be the grandfather to Ursa, Zuko and Azula's mother, the latter being 14 at series start. Roku died about 12 years before Aang was frozen (and the War began), so 112 years before the series's beginning. ''[[ComicBook/AvatarTheLastAirbenderTheSearch The Search]]'' shows Roku to be Ursa's maternal grandfather, with Roku's daughter and Ursa's mother being a woman named Rina. Even if Rina was born right before Roku died, she and Ursa must have given birth at the age of ''49'' years at the very least. When you also take into account how Roku and his wife were quite old when he died (they had a ChildhoodFriendRomance, so they're about the same age) and that Ursa is clearly younger than 50 during the flashbacks to Zuko's childhood, there's no way Rina could have possibly given birth to Ursa before the onset of menopause.
** Similarly, Shyu (who was 60 during the show) mentioned that his grandfather knew Avatar Roku. We later see that his grandfather Kaja was the Great Sage when Roku was about 26 and looked to be at least in his 50s. This would make Kaja at least 140 (probably more) years older than his grandson, and Shyu seems to imply that he personally knew his grandfather.
** Koh the Face Stealer mentions stealing the face of an Avatar's lover 800-900 years ago. We later learn that the Avatar he was talking about was Kuruk, who was only born less than 400 years previously. Possibly a retcon.
* In ''Dr. Quantum in Flatland'', Dr. Quantum attempts to demonstrate how a 3D object projected into a 2D plane would confuse those who inhabited a 2D world because they would not perceive three dimensional depth. However, the graphics depict Flatland as being 3D and having depth, instead of being purely 2D.
* In ''WesternAnimation/HeyArnold'', Grandpa Phil once mentioned that his grandfather lived in 1830-1921. In the same episode, Phil turned 81, implying he was born in 1915 at the earliest (if the show was set the year it premiered) meaning that his grandfather would've died when he was 6, yet we see a flashback in one episode where his grandfather was shown to be alive and well when Phil was about 9-10. We are also told that he was alive in 1926 (five years after his supposed death). It's likely that he got some years mixed up though.
** In the movie Phil mentions that his grandfather participated in the Tomato Incident which took place in the 1770s-1780s.
** Minor example, but he also mentioned that his father won the boarding house in a card game in the 1890s. In all the flashbacks we see of Phil's childhood in the 1920s, his father looks no younger than his 40s.
* The ''WesternAnimation/AmericanDad'' episode "The Kidney Stays in the Picture" has Stan and Francine go back to the year 1996 to ensure that their daughter Hayley is conceived. The problem occurs up when you realize that the episode aired in 2012. This would make Hayley '''16 years old'''. Seeing as how she's a married college student, that doesn't seem likely. Especially since the episode's plot is kicked off by her binge-drinking at a restaurant with her mother.
* ''WesternAnimation/FamilyGuy'':
** Quagmire was stated to be born in 1946. This is a deliberately implausible retcon that's played for laughs; in "Fist Full of Meg", he stated he went to high school in 1986, when he would be at least forty. On top of that he's shown, in a previous episode, to be an older adult in 1988.
** In "Back to the Pilot", pairs of Brian and Stewie arrive via time travel and vote on 9/11. Before the vote, the [[BehindTheBlack on screen]] crowd appears too small to make up the final tally of 99; after the vote, the crowd appears over twice as large as the number of votes counted, meaning out of a much larger crowd, not everyone voted. They question why the total number of votes was an odd number (Peter would make the number odd anyway, but Peter votes yes and no, cancelling his own vote); out of fifty pairs who voted, one Brian got killed, as if there were only one hundred pairs present. Could be [[HandWave handwaved]] by the number of Stewie and Brian pairs continuously time-travelling in during the vote and being counted in the spur of the moment.
* ''WesternAnimation/CatDog'': In the episode "Smarter than the Average Dog" when Cat becomes a genius he exclaims "Circumference equals Pi radius squared!" Pi radius squared is the area of a circle, not the circumference.
* The TimeTravel episode of ''WesternAnimation/DarkwingDuck'' has the eponymous hero go back to the 1950s, when he was in elementary school. A different episode seems to depicts him attending high school in the 1970s, if the clothes and hairstyles of the students are any indication.
* In an episode of ''WesternAnimation/ThePowerpuffGirls'', the girls traveled back in time to the 1950s and met [[EveryoneWentToSchoolTogether The Professor, Ms. Kean, and Sara Bellum in elementary school]]. Since the show was at various points indicated to take place around the same year it was made (1998-2005) that'd make those characters in their mid-to-late fifties, and they just don't look like it.
* Mostly {{averted|Trope}} in ''WesternAnimation/{{Futurama}}'', where several of the writers have [=PhDs=] in mathematics. Hell, they'll take breaks at some points in the DVD commentaries just to talk about math.
** Notably averted in ''The Prisoner of Benda'' when one of the writers ended up ''proving a new math theorem''. See [[http://www.geekosystem.com/futurama-prisoner-of-benda-theory/ here]]
** [[RunningGag Constantly]] [[ParodiedTrope made fun of]] with Bender's composition materials. He often remarks how he's 30 or 40% of something (Iron, Titanium, Scrap Metal, Lucky Horseshoes, Film/{{Dolemite}}, Zinc, etc.) which accumulatively sums up to between 150% and 330% or more!
* The citizens of Mainframe in ''WesternAnimation/ReBoot'' exist inside a computer and, as such, live their lives at a much faster rate than we do; i.e., a nano spent in Mainframe is like a minute/hour spent in real life, a second is comparable to a day, a minute to a month, etc. However, time runs faster inside the Games, which is how Enzo and [=AndrAIa=] could [[PlotRelevantAgeUp grow up]] in Season 3. So... how can the User play games so quickly? Shouldn't games change time in the exact ''opposite'' manner?
* In ''Disney/BeautyAndTheBeast'':
** According to a lyric in "Be Our Guest", the castle has been under the Enchantress's curse for 10 years. Since the rose stopped blooming once the Beast turned 21, this would mean that he was 11 years old when he was cursed. This does not match up with the stained glass windows in the prologue or the portrait of his human form in the West Wing, which show him as a young adult (not to mention that the curse comes off as a lot crueler if he was a child when he was affected).
** Another issue up for debate is the span of time over which the main events of the movie take place. The movie appears to start in autumn ("Belle"), then quickly goes into winter (the "Gaston" reprise). The famous title song dance scene takes place on a warm night (complete with crickets chirping), yet that same night after Belle is released, there is still a foot of snow on the ground. ''Later'' that same night, there is a torrential thunderstorm, suggesting that it is spring, which means [=LeFou=] would have been waiting for Belle and Maurice to come home for the entire winter.
** Maurice sets out for the castle to save Belle when the Beast is still animalistic and unrefined. When Belle looks into the mirror and sees him out in the woods, the Beast has become gentler and has fallen in love with Belle. Does that mean Maurice was out in the woods for weeks or months on end, or was the Beast reformed in the span of one or two days?
** The various direct-to-video films and other follow-ups don't help with this issue. Enough time passes in the castle that they celebrate Christmas, for instance. The PerspectiveFlip novel ''[[Literature/ATaleOf The Beast Within]]'' scraps the movie's implication that the Beast was cursed when he was only eleven years old, but keeps the condition of the curse becoming permanent when he turns 21. But it's not clear at all how much time passes over the course of the story -- he is old enough to be engaged when he's cursed, several months pass as the curse begins to take effect, and years pass after that. Thus the Beast's age remains in doubt.
* ''WesternAnimation/BatmanBeyond'' originally took place in the year 2039, being referred to as taking place forty years after the end of ''WesternAnimation/BatmanTheAnimatedSeries'' (1999). Later on, the [[WordOfGod creators of the show]] announced that the show takes place fifty years after the end of ''WesternAnimation/JusticeLeague Unlimited'' (2006), meaning that would [[RetCon place the date at 2056 instead]]. However, the characters make explicit references to events that happened in the previous series [[SeriesContinuityError as being no more than forty years ago]]. [[AllThereInTheManual Certain sources]] even give Terry [=McGinnis=] a birthdate of 2023. And now, the 2010 ''Batman Beyond'' comic series [[FlipFlopOfGod once again confirms the date as being 2039 and thus only forty years passing]].
** For a lesser example, Batman Beyond 2.0 issue #16 has Barbara expressing her belief to Dick that he's held Sam against her for twenty years [[note]]both are in their mid-late sixties at this point[[/note]], but the flashback to the day of Barbara's wedding depicts both characters looking as they did in the 90's cartoon, when they were (presumably) in their early-mid 20's. Could be a case of them [[OlderThanTheyLook still looking young for their age]] in the flashback, but still worth noting -- especially since Commissioner Gordon is shown as alive.
* ''WesternAnimation/DextersLaboratory'':
** When Dexter has to pay off a $200 million debt to NASA in "Dexter's Debt", he gets one dollar and then says he only has $199,9'''00''',999 to go. Someone forgot two nines.
** In "Nuclear Confusion", Dexter tells his computer to decipher a clue Dee Dee left to find something she stole from him, namely "r squared". The computer then figures it meant to check the pies his mother made, because [[{{Pun}} pi(e)]] equals r[[superscript:2]]. That's not true; it was probably supposed to be how pi '''times''' r[[superscript:2]] equals the area of a circle--the correct formula was even shown on-screen.
** "Ice Cream Scream" centers on Dexter trying to buy ice cream from a vendor [[BadHumorTruck that hates him]] for buying a ridiculously expensive item [[PayingInCoins with pennies]], [[DisasterDominoes indirectly ruining his life]]. Him counting the pennies at an "average human rate" took about five-and-a-half hours, and the on-screen price for the items was $16, thus 1600 pennies. That would mean the ice cream man was counting at the ridiculously slow pace of about ''12 seconds'' per penny--it would have taken less than an hour even if took two seconds each, which is still fairly slow.
* It appears the ''WesternAnimation/TotalDrama'' writers have problems with basic counting in some instances: for example, whenever Chris has to count the amount of campers left during a challenge (in the second episode of ''Island''). Or, when they said the tenth camper to arrive on the island was "contestant number nine", which may be the root of the Trent problem from season two, either that or Chris lost track of the head count. They also can't seem to figure out exactly how much time passes between episodes. Sometimes, the characters say it was a week since the last episode, which would require ''Island'' to last 24 weeks, not eight. It's usually said that there are three days between challenges, though, which still means about 72 days, or about ten weeks. For that matter, the time counter in the second episode means that that episode's challenge lasted for three and a half days, and that some of the campers slept continuously for most of that.
* Jane from ''WesternAnimation/TheJetsons'' is thirty-three, and her oldest child is seventeen. Unless adopted, she had her at [[TeenPregnancy sixteen years old]]. We doubt it was intentional, since the series is from the '60s.
* Three Creator/FrizFreleng cartoons from the [[WesternAnimation/LooneyTunes Warner Bros.]] stable have this problem.
** In ''Boulevardier From The Bronx'' (1936), Dizzy Dan's team the Giants is already up 2-0 when they score two additional runs (on an inside-the-park homer and a four-base error) which made the score 4-0. But in the bottom of the ninth, where pitcher Dizzy Dan intentionally walks the bases loaded just so he can strike out hayseed Claude (who winds up hitting a grand slam), the scoreboard reads 3-0.
** In 1946's ''Baseball Bugs,'' In four innings the Gas House Gorillas score 96 runs against the Tea Totallers. Enter Bugs Bunny, assuming all nine positions for the Tea Totallers and scores 96 runs himself. However, the score in the bottom of the ninth reads Bugs Bunny 96, Gorillas 95.
** In "The Wabbit Who Came To Supper", going by the deductions as listed in the special delivery letter, Elmer is actually left with a final balance of $902,934.04, rather than owing them $1.98.
* In Creator/ChuckJones's 1945 cartoon ''Hare Tonic'', Bugs asks Elmer a couple basic multiplication questions. When asked to multiply "3 x 3", Elmer replies "6." Bugs does not call him out on this.
** He didn't have to. He was just making Elmer think he was a rabbit because he was "multiplying."
* Frank Tashlin's "Porky Pig's Feat" (1943) shows Porky and Daffy's hotel bill, which is totaled at $152.50. A second look at the bill and adding the items all up ($65 room, $20 bath, $32 bed, $15 air, $12.50 sunshine, $17.50 goodwill and $10.50 extra goodwill) shows an actual total of $175.50.
* In ''WesternAnimation/SamuraiJack'', the bounty that Aku places on Jack's head is a "googolplex" of whatever currency he uses. This is impossible, no matter what the value is of that standard of currency. A "googolplex" is a number used to express metaphysical ideas, as is described as a one with a "googol" of zeros after it. First of all, a "googol" is a one with a hundred zeros after it, and even ''that'' number is so large that ''nothing'' exists in such a quantity. Even if all the atoms of every molecule in the universe were counted, it wouldn't equal a googol. As for a googolplex, simply writing out such a number would require more space than the universe has available and more time than its age. So it is safe to say that Aku's bounty is absurd.
* ''WesternAnimation/{{Animaniacs}}'':
** In a ''WesternAnimation/PinkyAndTheBrain'' short called "Puppet Rulers", the eponymous mice are living presumably in the 50s and the Brain frequently states that they will freeze themselves for forty years, though later on a caption reads "Thirty Years Later" and the Brain correctly acknowledges them as being in the 90s. (Maybe it was 1959, and Brain just rounded down.)
** In another ''Pinky and the Brain'' short entitled "Brain Meets Brawn", Pinky accidentally shrinks the Brain four times with his repeated apologies, then restores him to his normal size by hitting (and thus angering) him only three times, though it's possible that some instances shrink or grow him moreso than others, supported by the fact that Pinky's final apology at the end of the episode shrinks the Brain all the way down to the size he was after Pinky had apologized four times.
* ''WesternAnimation/DefendersOfTheEarth'' featured the 27th [[ComicStrip/ThePhantom Phantom]] in the year 2015. The show was made in 1986, and at the time the present-day Phantom was stated to be the 21st in line. The mantle of The Phantom is usually passed on from father to son, which would be quite a feat to do six times within 29 years. A later animated spinoff, ''{{WesternAnimation/Phantom 2040}}'' was more reasonable about this with its main character being the 23rd Phantom [[CaptainObvious (in the year 2040)]].
* In ''WesternAnimation/TheSimpsons'', Homer quotes the Scarecrow attempting to describe the Pythagorean theorem in ''Film/TheWizardOfOz'', when a man in a bathroom stall corrects him with, "That's a right triangle, you idiot!" Because the original quote uses "square roots" instead of "squares", and does not correctly describe a right triangle or an isosceles triangle, the man's correction is still incorrect.
* In the ''WesternAnimation/XMen'' episode "Beyond Good and Evil", Cable and his team infiltrate the evil immortal mutant Apocalypse's secret temple in Egypt. Cable notes that Apocalypse has spread death and destruction for over 5000 years. Then he notes that they found his lair after 500 centuries of research (50,000 years).
* A ''WesternAnimation/TotallySpies'' episode implies the high school aged protagonists were tweens in TheEighties. The show takes place in the mid 2000s.
* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'':
** The series frequently refers to moons as a period, but no instantiation of the period makes any sense whatsoever. For example, if placed at a month the Apple Family Reunion, which takes place every 100 moons, would only take place every eight years, despite far less time taking place since the last reunion, while the magic mirror in Equestria girls only opens every 30 moons, which is ridiculously short for any reasonable time frame for the family reunion.
** How much time the train takes to get from Ponyville to Canterlot is also wildly inconsistent.

--> ''"80% of you have no understanding of percentages!"''
--> ''"We aren't even that many..."''