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In Super-math it may be 32,000. But in regular math, it's 3,200.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.
Calvin and Hobbes II: Lost at Sea (a Script Fic that imitates a movie)
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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. It can also come from multiple writers not checking with each other, or screwups in the timeline.

Compare Soap Opera Rapid Aging Syndrome, Not Allowed to Grow Up, and Longest Pregnancy Ever, where the writers can do math — they're just intentionally fudging it. See also Sci-Fi Writers Have No Sense of Scale and Not Drawn to Scale. Possibly the root cause of Everybody Hates Mathematics. Might even involve E = MC Hammer. Artistic License – Statistics is a subtrope.

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A natural habitat of the MST3K Mantra and Fan Wank, as in many cases, these errors are not important for the plot (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 16 are 3.141592653589793. Also, the first thirty-two for the square root of pi are 1.7724538509055160272981674833411.


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Examples:

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    Anime & Manga 
  • 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, physically 18.
      Goten is 7 when we first see him, but just under 7 years went in-between the Cell saga and its Time Skip 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 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, Mai of the Pilaf gang, who 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.
  • Naruto has numerous inconsistencies with character ages compared to state time periods, mostly because these ages are only in the databooks, so the author either doesn't remember them or 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 Killer Bee is fighting Kisame there are some counting errors in the art: When he starts going into his 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 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 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 (Kakashi even outright stated this during the Team 7 bell test). The academy 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. And that's not taking into the account the fact that Konoha was involved in three other world wars and countless other conflicts (including the Uchiha Clan Massacre) that no doubt had taken out a large chunk of its ninja population...
    • Even disregarding the above, Konoha, with its several hundreds-odd non-high rise buildings until the Boruto series (since it's still technically, y'know, a village), doesn't seem to be the type of community that could support tens of thousands of commoners, let alone ninja, though this can be easily handwaved by thinking that Konoha ninja don't necessarily all come from the village and instead hailed from elsewhere in the Land of Fire.
    • 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 single 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.
    • It's mentioned that Naruto has failed the academy graduation test several times. This doesn't make sense because it's been shown he began the same age as everyone else. Naruto is actually several years younger than the rest of the Konoha 12.
  • In an episode of Digimon Savers, 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 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. Oops.
  • In the original version of Yu-Gi-Oh!, 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. This was corrected in the dub version.
  • In Yu-Gi-Oh! GX, 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.
  • Steins;Gate, 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 changing her child's sex from male to female. However, it's been established that one second on the Phone Microwave (name subject to change)'s timer corresponds to one hour back in time, and seventeen years is about is 150,000 hours. The microwave's counter 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 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 Black Butler 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 MegaMan NT Warrior, 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 Fairy Tail 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.
  • Rave Master:
    • 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 Quirky Miniboss Squad 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.
  • Bakuman。, or rather, 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 Assassination Classroom, 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 Fullmetal Alchemist Brotherhood Isaac Mcdougal says at one point that water is over 70% of his body. There is an in-universe formula for human bodyingredients  and according to this formula water is about 60% of human body.
  • In the H-managa Dulce Report II, a principle character is said to age at a rate of five times faster than a normal person due to LEGO Genetics. However, she appears to be a Second Year Protagonist and her conception happened five years ago not three. As there is no mention of her gestation taking longer or shorter the math doesn't agree with what is stated having her age at rate of around 3 times, give or take a few weeks, faster.

    Comic Books 
  • The Flash 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 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.
  • Justice Society of America member Stargirl is explicitly stated to be sixteen years old early in the book's run, and is still that old later on. Then, 52 and One Year Later happen as a Time Skip 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. 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 Wonder Girl. Possibly subverted with Tim Drake (Robin), 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 Ultimate Fantastic Four 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 X-Men, 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.
  • ElfQuest's timeline is by now properly beyond all help, because of too many authors Running the Asylum. Particularly Mantricker's timeline, the era between Goodtree's rule and Bearclaw becoming chief, makes no sense whatsoever anymore.
  • Superman demonstrates "Super Math" in this comic panel, but the writer is 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 Tintin book 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 Canon Discontinuity miniseries Trouble purported to reveal that Aunt May was actually Peter Parker's biological mother. Problem is, writer Mark Millar 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 Human Popsicle?
  • In The Order by Matt Fraction, Ezekiel Stane claims a trap is 'surrounded by 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 New 52, Bruce Wayne has only been 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 Author's Saving Throw by establishing that Batman has been active for much longer than six years, but was only considered an Urban Legend prior to that, but even that was proven false with Scott Snyder's "Zero Year" arc. Then it was just implied that Damian had accelerated aging.
  • Similarly, Nightwing has historically presented a massive issue for DC timelines, being one of the few characters with a hard timeline. Becoming Robin at 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 Green Arrow prior to the New 52, 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 Teen Titans 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 affair with villain, Chesire, born before Harper became Arsenal, led the Titans, joined the Outsiders, joined the Justice League, etc. By the time of New 52, it was clear that the affair would have to have happened while Roy was a minor.
  • Once Don Rosa created a timeline for certain events in the Disney Ducks Comic Universe to establish the Continuity Porn used in his The Life and Times of Scrooge McDuck, 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 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 Astérix, 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 legionariesnote , this puts the size of the Gaulish village at four people. Even if Convolvulus meant 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.
  • The Flash created a huge problem for itself with Wally West II. Originally, Wally II was the New 52 Wally West, the thirteen year old son of Rudy and Mary West and nephew of Daniel West, the Reverse-Flash. Then Rebirth happened and brought the original Wally back, retconning Daniel into being Wally II's dad while also giving Wally II an Age Lift so that he's sixteen. The problem is, a key part of Daniel's backstory is that he's a Cosmic Plaything, and he explicitly states that he was caught by the Flash on his eighteenth birthday, which meant he was tried as an adult. He spent five years in prison, and when he's released, he becomes the Reverse-Flash not long after, and current stories took two years to play out. Unless it took years for Daniel to be convicted of robbing a bank, he'd have had to conceive Wally II as a child.
  • Wonder Woman: In Issue #96, Angle Man traps Wonder Woman inside a Time Machine and sends her to the year 4457 but later says he sent her 2700 years into the future. By that math, he sent her from the year 1757.
  • In the DC Rebirth era, it's explicitly stated that Kate Kane is 27 years old and has been Batwoman for only two years. However, since Rebirth is a continuation of the New 52 and Kate herself was not rebooted with the New 52, this causes some problems. Since Kate appears both at the start and tail end of the New 52, that would require the entire New 52 to happen in two years, which is simply not possible. It also requires her to be de-aged at least 5 years, which conflicts with a scene of her attending the Waynes' funeral; Bruce is 8 in that scene, and Kate seems about 5 or 6 and cannot be older than he is.
  • Black Canary is sometimes treated like a Parental Substitute towards Roy Harper. This made sense pre-Crisis, when she was in her 40s while Roy was a teenager, but doesn't work post-Crisis. Dinah was aged down a good 20 years, meaning that the two are less than a decade apart.
  • Rorschach from Watchmen was born in 1940. His police folder includes a school report he wrote when he was 13 but it's dated 1963 when he would have been 23.

    Comic Strips 
  • The Dick Tracy 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.
    • Presumably the writer forgot that there were 12 inches to a foot, not 10.
  • 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.

    Fan Works 
  • In Light and Dark The Adventures of Dark Yagami, a "sevensome" goes on between six people: Sayu, Misa, Dark, Light, Light's mom and the girl from the bus.
  • Exploited in George Weasley and the Computational Error. Because J. K. Rowling 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 computational error and not something to worry about.
  • One of the few mess-ups in Dead Garden 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 Gensokyo 20XX 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 Comic-Book Time. 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 Kill la Kill AU, 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.
  • Ace Attorney fanfic Her Life or Mine gets about every canon date or relative age wrong.
    • Fanfic takes place between Hazakura case Note  and Phoenix's disbarment Note  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 he was disbarred Note  there is no way to squeze in over a year between them.
    • 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 Cellar Secrets 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 Ace Attorney fic, The Fated Turnabout takes place in 2018, and Lyn goes on a date with Larry on Sunday, April 18th. That date in 2018 was a Wednesday.

    Film — Animation 
  • Beauty and the Beast:
    • 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 Perspective Flip novel 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.

    Films — Live-Action 
  • π:
    • 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, 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 the script.)
  • In Captain America (1990) the boy who would become The Red Skull is kidnapped by government agents to make him a super soldier, it is stated that seven years pass when Captain America comes to rescue him by this point he appears to be in his mid-late twenties, this doesn't add up at all because if he was abducted when he was 10 the oldest he'd be is 17.
  • Judge Dredd gives the crime rate in Mega-City One in 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.
  • Aliens:
    • There are several problems with the Director's Cut, which restores several scenes. The first is that there are only about 150 colonists on the planet, which means a maximum of about 150 aliens (it's unclear how many colonists were not successfully impregnated and died other ways). This isn't too bad a problem with the theatrical cut, but the Director's Cut includes scenes of 4 Sentry Guns with 500 rounds apiece blasting away at the aliens when they attack in a Zerg Rush, with the camera showing scores of aliens killed. There are also plenty of aliens killed throughout the rest of the movie by the Marines. And yet, when attempting to escape, the motion trackers light up with what looks to be 50-100 aliens at least converging upon them.
    • Also, the same scene that introduces the Sentry Guns also shows the remaining marines only have about 50 rounds apiece in their rifles, yet they clearly fire way more than that when they try to rescue Ripley from the Med Bay and in the subsequent base assault and retreat through the air shafts.
    • Both versions of the film also have the alien attack on their sealed base, while Hudson is reading the distance to the closest target. When he reaches 6 meters, they start arguing because they realize that the aliens would be inside the room at that point. Problem is, Hudson keeps counting down the distance before they get their realization that the aliens are coming from above and/or below them, getting down to 3-4 meters. The marines then spend a good 10-20 seconds realizing what's up and figuring out a way to take a look in the shaft above the ceiling. Apparently, the aliens decided to be good sports and stopped moving while they were discussing matters, or the writers didn't think that anything less than 2 meters is basically within touch range and Hicks wasn't going to get a chance to look above the ceiling tiles.
  • 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.
  • In Forrest Gump, Forrest claims that Jenny died on a Saturday, and yet her gravestone says 22 March 1982, which was a Monday. Odd that Robert Zemeckis would make that mistake, considering he so thoroughly avoided it in the Back to the Future films.
  • The prologue of the original Halloween 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.
  • The Heavenly Kid has the title character die in what is clearly the late '50s or early '60s. He's then brought up to The Present Day (1985) and discovers he sired a son, who's now in High School. Apparently, his son had to repeat a few years.
  • In Home Alone, Kevin is 8 years old; in Home Alone 2, Kevin is 10, the same age as actor Macaulay Culkin, who plays him, was at the 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.
  • It's a Wonderful Life:
    • 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.
  • In the James Bond movie Goldeneye, the Big Bad 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 Wii remake of the original game of the movie: since the game is set in the present day, said Big Bad's motivation is changed to 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 Big Bad could indeed have been born.
    • It should be noted that the character was originally written as a mentor figure to Bond, with Alan Rickman and Anthony Hopkins both considered, who would have both been the right age.
  • Kelly's Heroes, a World War II film, features a bank heist of 14,000 bars of Nazi Gold 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.Kellys Heroes page for all the gory details.
  • Mamma Mia! 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 1976 (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 (Pierce Brosnan'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's character, 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!
    • Bad, but not quite that bad. The problem comes from trying to make a film in 2008 based on a play from 1999, based on music from the late 1970s. The three women were in a group in the 70s, supposed to be based on the Grrl Power movement. It would have been better if they were playing instruments; there were many female singing groups before that, but still a lot of prejudice against women who played their own instruments as seen in The Runaways. As to what Brosnan was wearing, he looked more like a hippie but lots of people identified with and wore clothes from an earlier generation. The problem is the song "Our Last Summer"- it was about 1967 or 1968 (the time of flower power) and released in 1980; it would have fit in perfectly about a young couple in their late thirties talking about their early twenties.
  • 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 Conjunction Interruption; we don't know what the boy was going to say, but it could have been to note that fact.
  • In Mean Girls 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 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.
  • Alex O'Connell's age in The Mummy Returns. 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 Never Been Kissed, 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 The '80s, 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 The Smiths, music more apropos of what should have been their grade school years.
  • In Night at the Museum: Battle of the Smithsonian, 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.
  • 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?
  • Ace Attorney: 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.
  • In Roxanne, a modern-day remake of Cyrano de Bergerac, C. D. Bales agrees to make twenty jokes about his own nose. Apparently he and the rest of the bar patrons lost track. He actually did twenty-five jokes. (Word of God says the bar knew and just wanted C.B. to do more insults.)
  • Scanners: Darryl Revok reveals himself to be Cameron Vale's older brother, then tells him that one of them was born in 1943, the other in 1948. Earlier in the film both characters are stated to be thirty-five years old by Dr. Ruth. Either their birth dates are incorrect or one of their ages is.
  • A Serious Man: When Larry scrawls the equations of the uncertainty principle on a chalkboard, he miswrites one of the equations as "Δp = √(<p>^2 - <p>^2)", making the equation the square root of zero (which is zero). The correct equation is "Δp = √(<p^2> - <p>^2)".
  • Played with in Stranger Than Fiction: 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.
  • Marvel Cinematic Universe:
    • A line in Thor: Ragnarok ("We were eight at the time.") hints that Thor and Loki might have been raised as twins, and the Minor Kidroduction at the beginning of Thor shows them looking the same age (both actors were 11). However, while Thor shows that the battle against the Frost Giants was in 965 (which is also likely Loki's birth year), 1053 years before the events of Avengers: Infinity War, in this film Thor states that he is 1500 years old.
    • The opening scene where Toomes is cleaning up the wreckage from the Battle of New York is stated to take place eight years before the rest of the scenes in Spider-Man: Homecoming. However, this is impossible. The Battle that was shown in The Avengers (2012) occurred in 2012 (as confirmed in Agents of S.H.I.E.L.D.), after the May 2011 Stark Expo (as seen in "Fury's Big Week"). And main events of Homecoming take place in 2016, a few months after Captain America: Civil War, before the second and third acts of Doctor Strange (2016) and before the events of the fourth season of Agents of S.H.I.E.L.D.. In Civil War Vision makes a reference to Tony Stark revealing himself as Iron Man to the world eight years ago, and Iron Man was released in 2008 and has been understood to take place in either 2009 or 2010. To complicate the matter futher, Aaron Davis is mentioned to be 33 years old in Homecoming, and his criminal record states a birth date of April 1984, which would set the rest of the movie in 2017 rather than 2016. The "Eight years later" thing was admitted to be an error.
  • One scene in St. Trinian's 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.
    • The scene has three characters make the same mistake: the contestant (a student at a presumably top school), the bursar (a numbers man), and Stephen Fry. It's...odd, to say the least.
  • At the end of Summer School, 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 Super Mario Bros., 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.
  • Terminator:
    • The Judgment Day was to occur August 1997. John Connor was born February 1985. Terminator 2: Judgment Day shows him at the age of ten being attacked by the Terminator. Terminator 3: Rise of the Machines then Retcons 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.
  • Transformers: Revenge of the Fallen: 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.
  • The Wizard of Oz: 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." This is lampshaded in The Simpsons, 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 "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.
  • In X-Men: First Class 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".

    Music 
  • 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 Stephen King wrote the narration.
  • The Rage Against the Machine 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 The Clockwork Quartet magnificently details an Apocalyptic Log 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.

    Myths & Religion 
  • The people of the northern 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, the numbers match quite accurately.

    Pro Wrestling 
  • Scott Steiner's infamous promo for a match against Samoa Joe and Kurt Angle in TNAnote :
    -> "You know they say all men are created equal, but you look at me and you look at Samoa Joe and you can see that statement is NOT TRUE! See, normally if you go one-on-one with another wrestler you got a fifty/fifty chance of winning. But I'm a genetic freak, and I'm not normal! So you got a 25 percent at best at beating me! And then you add Kurt Angle to the mix? You-the chances of winning drasticy go down. See, the 3-Way at Sacrifice, you got a 33 and a third chance of winning. But I! I got a 66 and two thirds chance of winning, cuz Kurt Angle KNOOOWS he can't beat me, and he's not even gonna try. So, Samoa Joe, you take your thirty three and a third chance minus my twenty five percent chance (if we was to go one on one) and you got an eight and a third chance of winning at Sacrifice. But then you take my 75 perchance-chance of winnin' (if we was to go one on one), and then add 66 and two thirds…percents, I got a 141 2/3 chance of winning at Sacrifice! Señor Joe? The numbers don't lie, and they spell disaster for you at Sacrifice!"

    Tabletop Games 
  • In the 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 Warhammer 40,000, 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.
      • On the other hand, this very issue (measuring "effectives" versus larger metrics) is a real thing with armed forces. It's quite possible for a real world force nominally described as 1,000 men to mean either "1,000 enlisted combatants plus officers and hundreds of supporting elements" or "about four hundred combatants, three hundred supporting elements, forty officers, sixty sick and two hundred absent or dead".
    • The Rogue Trader 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 Dark Heresy have some... weird blast radius. Promethium, especially, is ridiculously volatile. During a session, a supertanker filled with five hundred million 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 Warhammer Fantasy Roleplay, 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 Role Master'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 Role Master, after all, the Dwarf Fortress of pen and paper RPGs) 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.
  • Dungeons & Dragons:
    • 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 10-foot ladder could be purchased for 5 copper pieces, split into two 10-foot 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. 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" stylenote , 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 weight, and neither does acid, holy water or 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 leveling 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 optimizers tend to dismiss the truenamer as utterly useless.
    • They had the same mechanical problem with 4th Edition. Monster design explicitly had the Defenses of monsters increase by one for every level of the monster. So, a level 30 monster had +29 more to their AC, Fort, Reflex, and Will than a level 1. Problem is, you could only get a natural +1 for every two PC levels, which meant +15 at level 30. You could also increase your stats by a maximum of +7 each from leveling (+1 to 2 stats every 4 levels), with an automatic +1 each from levels 11 and 21. But, each point only increased the stat bonus by 1/2. So, a level 30 PC who put every stat point into their main stat got maybe +5 to the bonus, and along with having a +6 (the best) weapon/implement, P Cs were still behind on the curve even if they min-maxed. Wot C clumsy solution to the problem was to create a Weapon/Implement Focus Feat that allowed you to get +1 for every 10 levels. So, you had to take a Feat, put every stat increase into your main stat, and have the best possible weapon/implement just to keep up.
    • 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.) Though considering that Death Is Cheap, it might not be as ruinous as it sounds.
    • Plenty of stats given out for population sizes, overlapping with Sci-Fi Writers Have No Sense of Scale, seem way too small or too large for medieval cities. The City of Greyhawk, for instance, is the largest city on the continent and has a population of about 70,000. This is about half of what Paris had in 1450, right after being hit by multiple plagues and repeatedly attacked in the Hundred Years War — and this is after Greyhawk's numbers were retconned to be significantly higher. Sometimes this is played with or justified.
  • Some of the early Star Wars 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 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 Werewolf: The Apocalypse, 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 Iron Kingdoms, casualty figures for Cygnar indicate that its entire population has been wiped out. Twice. Most nations only manage it once.
  • 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.

    Theater 
  • The Phantom of the Opera takes place in 1881. Its sequel, Love Never Dies, 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 here.
  • The Pajama Game 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 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 Fiddler on the Roof after a Time Skip, 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.
  • Charlie and the Chocolate Factory falls afoul of this in Act One with regards to Veruca Salt finding her Golden Ticket. In the "I Am" Song "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 Veruca Salt here.) This might be a matter of the book and the lyrics being penned by different writers.

    Toys 
  • BIONICLE has this across its multiple forms of media.
    • The size of the Great Spirit Robot was increased from its originally intended height (about a small-to-middle sized continent) to roughly the diameter of Earth without other measurements being changed accordingly. This means the Denmark-sized island that was supposed to be covering the fallen robot's head would't have fit.
    • Practically all forms of media disregard any given measurements when depicting the sizes and population numbers of cities or villages. Depending on which part of the story you're looking at, the population of Metru Nui/Mata Nui can be several thousands, exactly one thousand (plus its small group of leaders and protectors), or just dozens. The online games have an excuse in that they couldn't possibly have programmed that many characters.
    • Water began pouring into Karda Nui through an island-sized hole, which under a thousand years only managed to flood its bottom. While Karda Nui is a gigantic place and its sizes can only be guessed at though comparing different pieces of concept art, fans have calculated that even under the most lenient of circumstances, the place would have been filled with water in a matter of weeks.

    Visual Novels 
  • 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 Higurashi: When They Cry, 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 Super Dangan Ronpa 2, Monokuma reveals that 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 Ace Attorney don't match.
    • In the final case of Trials and Tribulations it is stated that Phoenix dated "Dollie" for 6 months, when it was actually almost 8 monthsNote . Corrected in later ports.
    • In Apollo Justice onward, most of the Phoenix Wright-era cast are a year younger than they should be, because of the botched handling of a time skip. To explain further, the trial of Shadi Enigmar happened seven years prior to the events of AJ. When calculating character ages, the writers counted from the start of T&T instead of the end of T&T. (Further confusing things, everything still takes place in the year it's supposed to - only the ages are wrong.)
  • Zero Escape trilogy deals with a lot of science and math, both basic and advanced (mostly done by Akane), and most of the time it gets it right, but few mistakes managed to slip in:
    • At one point in Nine Hours, Nine Persons, Nine Doors Seven pulls up a theory that the ship they're on is RMS Gigantic(a real-life ship that was later renamed to HMHS Britannic), to which Santa reacts with "There is no way we're on a boat that's almost 100 years old". Gigantic was finished in 1914 and game takes place in 2027, so if Gigantic still existed it would be over 100 years old.
    • Zero Time Dilemma:
      • If you fail to get the correct code in the pantry, Carlos will say that a 4 digit-code has "hundreds of thousands of possible combinations". No, it doesn't: it has exactly 10,000 combinations. Akane makes a similar mistake in the infirmary when she claims there is over a thousand possible combinations for a 3-digit code when it's exactly one thousand combinations.
      • At one point, Akane says that the 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. The probability of getting at least one success with three attempts is 1 minus the probability of failing three times in a row. In this case it's 1-(215/216)^3, or more precisely 139,321/10,077,696, which is slighly lower than 1/72.

    Web Animation 
  • Homestar Runner: In Coach Z's music video "Rap Song", a featured guest singer proclaims, "My name is Tenerence Love, plus my name is Tenerence Love, divided by my name is Tenerence Love, equals my name is Tenerence Love...remainder 3." Depending on how the operations are grouped, the value of "my name is Tenerence Love" could be -1note  or it could not exist at allnote . 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 

    Web Comics 
  • Averted in Schlock Mercenary 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. (Quick link to the maths). Schlock's 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.
  • Angel Moxie: In-universe example. Grant accidentally fakes his birthdate as 1971, but the date of his teaching degree as 1983. Luckily, the only ones who notice are the heroines.

    Web Original 
  • 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.

    Web Videos 
  • The Nostalgia Critic, in his End of Days 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 he screwed it up. He later apologized for it in one of his "Fuck ups" specials.
  • Mario Party TV: 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)

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

Alternative Title(s): Writers Cannot Do Maths, You Fail Mathematics Forever

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