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Unit Confusion

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Pearl: Y'all couldn't touch the Pearl if you trained for 100 million light-years!
Marina: Light-years are a unit of distance...

Many times when a measurement is given, the units of measurement don't make sense for what is being measured. This is especially annoying when the character suffering from Unit Confusion is supposed to be a scientific genius.

This occurs frequently in Science Fiction. Compare Sci-Fi Writers Have No Sense of Scale. It also tends to happen in lazy localizations that blindly substitute one unit for another of the same type.

Averted when the writers use Fantastic Measurement System, as the writers can redefine time units whenever they like. If they care to keep it in mind.


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    Anime and Manga 
  • In Bleach, Ryuken Ishida tells his injured son that if he yell 5 Hertz louder he'll reopen his wounds (basically telling him to shut up), but Hertz is a measure of frequency (high or low) not intensity (decibels in the case of sound). The dub changed the line to "decibels".
  • Lampshaded in Doki Doki! PreCure's ending Dancing Theme, "Kono Sora no Mukou".
    No matter how many lightyears away it is, the future is not far off!
    Of course I’m well aware it’s not a unit of time.
  • The first English dub of Dragon Ball Z falls victim to this trope: When Bulma is explaining to the group why traveling to Namek would be impossible, she gives her answer in years, then promptly adds "And that's in light-years!" Perhaps Bulma is distinguishing years in an ordinary slower-than-light craft from years at c.
  • In Outlaw Star, a load of 5 tonnes of dragonite the crew pick up turns out to be far less valuable than expected. The explanation was that it was "low density"—except the mass was already stated, so the density wouldn't matter for how much it was. They probably meant to say "low-purity" (i.e. how much of the stone's mass was actual useable material).
  • Pokémon makes the Hertz/decibels mistake in an episode centered around Marill. This is especially egregious as the person making the mistake is supposedly an expert on this sort of thing; yet Marill had previously appeared in the series without the error being made.

  • Comedian Dr. Pete Ludovice has a routine where he suggests that men try to invoke Unit Confusion by reporting their penis size in nanometres.
  • In one of his routines, Tim Steeves opined that Americans think Canada is so cold because weather maps measure Canadian temperatures in Celsius and American in Fahrenheit, extrapolating that to a scenario where colonial explorers demarcated the border between the US and Canada because the temperature abruptly dropped forty degrees. note 

    Comic Books 
  • Disney Ducks Comic Universe: Scrooge McDuck has often boasted of his money bin storing "three cubic acres" of cash. An acre, of course, is a two-dimensional shape, and cubing it would create a geometrically-impossible six-dimensional shape. Although that would go a long way towards explaining just how all those countless billions fit inside that single building. handwave 
    • Done intentionally in a story where Brigitta has been visiting Scrooge and, seeing he has an oral thermometer giving out a temperature of almost a hundred, goes crazy with the frenzy of curing him from his tremendous fever. When Scrooge can finally get a word in, he points out she had wrongly assumed his thermometer gives the temperature in Celsius but it actually gives it in Fahrenheit. She demands he thank her for lowering his fever from almost a hundred to 37.
  • In the Dutch comic Heinz, the eponymous character asks what a light-year is, and the specialist responds that it is a year in which everything goes off without a hitch. This might be more of a malapropism, though. (It's a year when you get off light.)
  • This Invincible Iron Man panel gets the unit type right but royally screws up the SI prefix: a "picobyte" would be one trillionth of a byte. Must be really optimized code. Or a really ginormous character set! Osborn probably meant to say "petabyte" or 250 bytes.
  • In a book of The Scrameustache, one Galaxian captain orders to reduce the speed by 2 parsecs. Perhaps it was short for "2 parsecs per year," the way someone going 25 m.p.h. might say "reduce our speed by 2 miles."

    Comic Strips 
  • FoxTrot:
    • Parodied/subverted in a strip: Jason is playing a racing videogame while his mother is trying to get him to come to dinner. Jason, who had earlier said "Just a sec," clarifies that he meant a parsec; just until he drove an entire parsec in the game, which would take him over 10 million years.
    • Another time, Jason decided to take up baking, and mused over whether the 350 degrees he had to set the oven at were in Celsius, Fahrenheit, or kelvins.note  Peter sarcastically suggested that he rotate the oven almost a full circle. "Don't be silly, Peter."
  • Parodied in Frazz, when Caulfield points out rather loudly that light-years are a measure of distance. The teacher then tells him to quiet down because he's "making a ton of noise."
  • A Mafalda strip has a teacher giving her students a math word problem where they have to calculate the area of a field measuring X by Y hectares. Amusingly enough, a later compilation featured an entire page of sketches by the author mocking himself for the mistake (the best is one where Susanita says "Hey Quino, you big idiot! How many liters are there in a kilometer?")

    Fan Works 
  • In The Prayer Warriors Threat of Satanic Commonism, Benry sells 2,000 kilograms of drugs to Rika and Books for $10 per kilogram, which is quite cheap. Books then leaves with the 2,000 kg of drugs (over 4,000 pounds) too quickly for Grover to shoot him with a sniper rifle.

    Films — Animated 

    Films — Live-Action 
  • Event Horizon messes has quite a few lines which contain physics whoppers that can spoil its Cosmic Horror mood. The Lewis and Clark is a space ship which develops a breach in the hull. Smitty claims that the ship has 218 liters of air left. But a body of gas fills up however much space the container that holds them has, meaning they should have measured how much was left in mass or pressure. Additionally, 218 liters is not a very large volume. It's approximately forty-five gallons, which would fit in about a fifth of a cubic meter. In other words, a space about three feet long by three feet wide by a little more than half a foot deep. It seems that Smitty is talking about the air in the cabin, which has a volume roughly equivalent to that of a small ranch house. If 218 liters of air under Earth-like atmospheric pressure then expanded to fill that space, anyone without a sealed space suit (like Smitty) would be dying of irreconcilable pressure and temperature differences. If the ship stored reserve air, expanding that air from 218 liters to the size of the cabin would cause it to become very, very cold very fast, just like a can of pressurized air for cleaning electronics does when you lower the pressure quickly.
  • In Iron Man, Tony Stark tells Yinsen that his mini arc reactor has a power output of 3.2 gigajoules per second (i.e. 3.2 gigawatts). Yinsen says that it could power his heart for a thousand lifetimes, and Tony responds, "Or something big for 15 minutes". Gigawatt is a measurement of power, not potential energy, so Yinsen shouldn't know that. Tony may have decided it wasn't important enough to correct him.
  • In Plan 9 from Outer Space, one of the aliens says "Foolish humans, we have had space travel for eons of your light-years." An aeon being one billion years and a light-year being a measure of distance... (Then again, this is the same alien who said that "A ray of sunlight is made up of many atoms.")
  • In Sherlock Holmes: A Game of Shadows, Moran is credited as a hugely proficient rifle marksman for making a shot over 650 yards with a 7-8 miles per hour side wind. This is shown in a flashback, which shows a dark night with very harsh wind conditions. However, a 7-8 miles per hour wind would barely be perceptible, and the wind conditions shown would be pretty in-line with a 7-8 metre per second wind speed.
  • Star Wars:
    • The most famous example of all: Han Solo bragging in A New Hope that his ship can make the Kessel Run in "less than twelve parsecs". Parsecs are a unit of distance, not time. While this has been Retconned to death with constantly shifting backstories about skilled pilots shaving distance by flying close to black holes, even those omit that the parallax second is based on local (terrestrial) factors, specifically the radius of the Earth's orbit, and would have no meaning in "a galaxy far, far away". The script (especially earlier drafts) says that this bit of dialog was intentional and meant to paint Han as a blowhard, and if you watch the scene closely, Ben kind of rolls his eyes, seeing through Han's BS.
      • Another explanation offered was that the Kessel Run was between multiple points that were moving apart from each other, starting from Kessel. The implication was that to visit each point with a total traveled distance of only twelve parsecs was quite fast indeed.
      • To further confuse the issue, J.W. Rinzler's The Making of Star Wars makes the claim that a "par-sec is a navigational calculation, not a measurement of time; that is, the ship is fast because it's smart."
      • Solo: A Star Wars Story provides an official explanation: the safe route for the Kessel Run is 20 parsecs long, but Han took a dangerous shortcut that cut it down to a bit over twelve (because he had the more dangerous problem of transporting unrefined coaxium that was in danger of exploding unless he got it to a refinery ASAP). Amusingly, this is also consistent with the "Han is a blowhard" interpretation: as impressive as Han's feat was, he still didn't make it in "less than twelve parsecs" as he claimed, just also not fourteen like Rey thought.
    • In a rather literal meta-example of this trope, there was much confusion over the definition of the term "unit" from Attack of the Clones (when the Kamino cloners said that 200,000 units were ready and a million more well on the way). Many assumed it referred to a military unit (e.g. an entire battalion of troopers) and failed to notice when R.A. Salvatore's novelization (and Patricia C. Wrede's Junior novelization) stated it to refer to an individual clone. (They later took issue with Karen Traviss' Republic Commando Series, misattributing the problem to her.) In context, "unit" meant used a unit of product. After the Disney takeover and relegation of the novelization to Star Wars Legends, a new canon reference book, Star Wars: Complete Locations, made the more reasonable statement that "unit" was meant to refer to a full division of clones (conventionally ten to twenty thousand infantrymen or a couple hundred armored vehicles).
  • In the movie Stealth, the processing speed of the AI was given in "terabits per second". This is not a unit of processing speed, but throughput. Processing speed would probably be measured in MIPS (millions of instructions per second) or flops (floating point operations per second), though the processing speed needed to keep up with I/O rates in the Tbps would still have to be impressive.
  • In the second Taxi film, a policeman's French dialogue indicates that the protagonist's souped-up taxi was traveling at '200 kilomètres à l'heure' (200 kilometres per hour). In the English subtitles, this is blindly translated as '200 miles an hour'. It has no bearing on the plot, but it credits the vehicle as going much faster than it really is (124 miles per hour).
  • Used intentionally as a major plot point in This is Spın̈al Tap. While trying to work out a big, stadium-pleasing onstage stunt to help the show, Nigel draws plans for a Stonehenge monument on a diner napkin, and the monument is built to the exact specifications he wrote, 18 inches (18"), not the intended 18 feet (18'). This leads to "a Stonehenge monument on the stage that was in danger of being crushed by a dwarf." This has actually happened (in the opposite direction) to Black Sabbath in Real Life.
  • In Time Bandits, Robin Hood (played by John Cleese) asks one of the bandits how long he's been a robber, and the bandit gives his height: four foot one. Robin Hood stammers for a moment before politely responding, "That is a... long time, isn't it?"

  • An example of Russian Humor:
    Sergeant instructs the recruits: And water boils at 90 degrees!
    One recruit replies: Sir, the water boils at 100 degrees!
    The sergeant isn't amused and orders 20 push-ups. He goes to the office and checks out the book.
    He returns and says: Recruit, you are right! Water indeed does boil at 100 degrees. 90 degrees is a straight angle!


By Author:

  • Dave Barry:
    • In a travel guide, the comedian facetiously lists a kilometer as a unit of foreign currency.
    • Exaggerated in Dave Barry Slept Here, which gives the distance of West Berlin behind the Iron Curtain as "120 miles (325 kilograms) (30936.54 hectares) (2,342,424,323.3432 millipedes)." That's one unit of distance, one unit of mass, one unit of area, and one class of arthropod.
  • In one short story by Ernest Hemingway, a boy thinks he's dying of a fever, having heard that you can't live with one much more than 40 degrees, and he has one that's over 100. His father points out the difference between Celsius (the former) and Fahrenheit (the latter), comparing it to miles and kilometers. Justified, considering that the boy is young enough to not know.
  • Jules Verne:
    • Often times, the books contain measurements and spot-on calculations. However, when they were brought over to the UK and US the translator screwed up horribly on the conversions at first. Partly by not really even doing them, just replacing the metric unit with the rough alternative but keeping the numbers. For example, in the Mercier translation, a breakdown of rooms covering half the length of the Nautilus adds up to 105 feet, but should have been 35 metres or 116 feet.
    • Many people like to sound clever by pointing out that 20,000 Leagues Under the Sea is 60,000 miles, and thus impossibly deep (the deepest part of the ocean is less than 3 leagues down), but this figure is the distance traveled in the book, not the depth they reach. But "Twenty Thousand Leagues Whilst Under The Sea" isn't quite as pithy. Verne consistently used a metric league (lieue, if you wish) of exactly 4 km in his works, thus the name translates into 80,000 km or ~50,000 statute miles, or almost exactly double circumnavigation (there's only a single one in the book, due to inevitable deviations from the shortest route). However this again brings the confusion as in Belgium the metric lieue is defined differently than in France and corresponds to five kilometres instead of four.

By Work:

  • The Asterisk War: Irene Urzaiz uses the term "fanega" to describe micro-singularities she can fire at her opponents. The fanega is the Spanish bushel, a measurement of volume rather than of mass, force, or acceleration, any of which would be more apt for a Gravity Master.
  • Bored of the Rings has a footnote defining a league as "approximately 3 furlongs or only a knot short of a hectare." While in Real Life leagues were once defined in terms of furlongs, knots and hectares are altogether different types of units.
  • Marion Zimmer Bradley's Darkover: In the original version of The Bloody Sun, the protagonist is told that his matrix jewel can probably emit "only a few grams of energy." It could make sense since mass and energy are equivalent (E=mc2). But the speed of light is so large (300 megametres per second) that even a few grams of mass, converted to energy, would be tremendous. The bomb dropped on Hiroshima released as much energy as about 15 thousand tons of TNT ... by converting less than one gram of mass into energy.
  • Earth (The Book) ends with a survey for the reader to fill out as an "Application for Genetic Reconstitution by Aliens." One of the questions is "How many kilowatts would you say your brain produces hourly?"
  • In Encyclopedia Brown's defense, one story referenced this trope in its solution: a man claiming to be a sailor is revealed as a fraud because (among other mistakes) he refers to speed in terms of "knots per hour", when a knot is already a measure of time over distance, i.e. one nautical mile per hour.
  • Never Trust a Trailer: The inside flaps of the dust jacket of Eon by Greg Bear has the protagonists going a million "kilometers" into the future. In units used by nuclear and particle physicists (the speed of light is one, a pure number, making one second equal to 300,000 kilometres) this corresponds to going 3.3 seconds into the future, a time even The Slow Path reaches rather quickly. Fortunately, the book refers to a million kilometres in a completely different manner.
  • An in-Universe example in the first book of the The Hitchhiker's Guide to the Galaxy series concerns the unfortunate fate of the combined battlefleets of the Vl'hurgs and G'Gugvunts, sent out to annihilate humanity after it is discovered exactly who it was who started the terrible war between them. Unfortunately, due to a terrible miscalculation of scale, the thousands of horribly beweaponed warships were swallowed by a small dog.
  • A children's book called I'm Coming To Get You told the story from the perspective of a monster travelling across space wreaking havoc, all the while getting closer to Earth in order to "get" a small child. When the monster finally arrives it realises it horribly misjudged its own size and the child is actually much bigger than it and easily chases it away.
  • Used in Robert Asprin's Myth Adventures series; as a dimension-traveler stranded in a backwards world, Aahz has trouble with Klahdish units of time and often has to be corrected by his apprentice Skeeve. In one book Aahz hears someone coming and says they'll cross paths in a few seconds. When he sees Skeeve panic, he realizes that he messed up and, after hashing things out, amends his statement to a few minutes.
  • Perry Rhodan plays with, then in-setting justifies the "temperatures below absolute zero" version: in the first arc in which humanity and allies seriously and consciously have to fight off the self-styled forces of cosmic chaos, one of the latter's weapons is a phenomenon that does indeed cause objects caught in it to rapidly cool down to absolute zero and below... whereupon they simply vanish from a universe in which they can no longer exist. In reality, they end up getting displaced into another universe whose own 'absolute zero' is in fact several hundred kelvins below that of ours, a fact that is discovered once actual survivors of the whole process start to come back
  • In the short story Retrograde Summer, John Varley managed to use "light year" as a time span. On Mercury, a (solar) day lasts two local years, so you have a light year (when the sun is up), followed by a dark year (sun below the horizon)...
  • In The Screwtape Letters Screwtape uses "light-year" as a measurement of time.
  • In The Truth about Pyecraft by H. G. Wells, A fat man called Pyecraft persuades the Narrator (who has some magical recipes from his great-grandmother) to give him a potion to let him lose weight. Unfortuantely, while Pyecraft does lose weight, he doesn't lose mass, and ends up floating near the ceiling. More, the protagonist calls out Pyecraft's euphemism, pointing out his trouble is a result of saying he wanted to lose weight, when what he really wanted to lose was fat.

    Live-Action TV 
  • Andromeda: In the last season, Rommie refers to having been shut down for nanomillennia as if that's a long time. Nano- is a prefix meaning one billionth. One nanomillennium is about 31.5 seconds. One thousand nanomillennia is still less than one day. This might be considered a long time to a computer, but since Rommie had been offline for longer periods previously, that makes it a mistake.
  • Are You Smarter Than a 5th Grader?: In one episode, one of the quiz questions was "How many watts are used during one kilowatt hour?" (The answer given was 1,000, but the question as written is unanswerable since one kilowatt-hour can result from using 2000 watts over a half-hour period, 500 watts over a two-hour period, or any of an infinity of other possible combinations.)
    • Not to mention the fact that the phrase "during one kilowatt hour" is just plain wrong as it implies a kilowatt hour is a unit of time (it is a unit of energy, equal to 3.6 Megajoules).
  • Arrow: In one episode, tech genius Felicity claims that she has a teraflop of data to sort through. Teraflops are used to measure processing speed, not quantity.
  • Babylon 5:
    • In "Messages from Earth", one spaceship evades another by hiding in the atmosphere of Jupiter. The pressure on the exterior of the ship as it descends is given in "gravities", although gravities are a measure of acceleration and not pressure, which is very different.
    • An example involving a unit made up for the show. Early on, it was decided that time on the station would be measured in cycles, possibly to avert Two of Your Earth Minutes. Unfortunately, none of the writers seemed to be able to agree on what a cycle was equivalent to (i.e. is it an hour? A day? A minute?). The idea was scrapped before the end of the first season. This was Lampshaded in a later episode when Ivanova stated that she was going to hold some troublemakers in custody for a Drazi cycle, after which the problems they were causing on the station would be sorted out. The Drazi she's explaining this to laughs, and points out that a cycle is a Drazi year, not a Drazi month.
  • The Big Bang Theory:
    • Brought up in one episode. Penny is talking to Sheldon (a theoretical physicist) and says something like "I guess you would say 'light-years ahead of his time'". Sheldon responds, "I wouldn't say that. Nobody would. Nobody who knows what they're talking about, anyway."
    • In the episode "The Romance Resonance" Sheldon uses square meters instead of square centimeters, meaning his solution is off by 10,000. He asks Amy if she realizes what this means; she replies "Americans still can't handle the metric system?"
    • Also, in one episode, Sheldon argues with the Department of Motor Vehicles over their use of the term "Car length" in one of their tests questions, citing that "A car length is not a standardised unit of measure" and he has a point as different makes of car are different lengths.
  • Bones once referred to "Force in Newton-Meters". Unfortunately, the newton-metre is a unit of torque, equivalent to one joule per radian. The Newton-metre is also a unit of energy equivalent to the joule (as radians are dimensionless); in this case, the metre is the linear distance over which the force is applied rather than the distance from the fulcrum. Nevertheless, it's still not a unit of force, which is simply Newtons. However, force can be measured using a device called a "Newton meter", thus is can be measured by Newton meters, but not in Newton-metres.
  • Boston Legal: An opposing counsel threatened to "drag it out for light-years" if the main characters declined a settlement offer. (How far the pages will stretch?)
  • CSI:
    • "Overload" includes, among its many atrocities against physics, Grissom confidently stating that "terminal velocity is 9.8 meters per second squared". High school physics should be enough to know that metres per second squared measure acceleration, not velocity (terminal or other).
    • In the season 14 episode "Girls Gone Wild", the team tries to find a grow op in a small town by checking the power consumption of houses in the area. Unfortunately, they mix up watt hours and watts, leading to them describing an average home as using 900 kW and their suspect using a whopping 5 MW. That little town would have needed its own nuclear reactor...
  • Doctor Who: In "The Seeds of Death", the thermostat shows a temperature above 60 degrees Centigrade after being turned up by Zoe to incapacitate the Ice Warriors. It has the desired effect on them, but the humans show no ill-effects, not even breaking sweat. In reality, such a temperature would be deadly within minutes to humans.note 
  • Some sci-fi shows attempt to rectify such things by actually using the alien standards of time (see Microts). "Cycles" are a big favorite. Farscape is probably the most easily notable of these, with its microts, arns, and cycles. While a microt seems comparable to a second, an arn to an hour, and a cycle to a year, the actual usage definition seemed to be "An arn is longer than a microt and a cycle is a really long time." Since the scales for them were never actually defined, they were just as long as they needed to be for the show's purposes.
    • In "Through the Looking Glass", Crichton asks D'Argo to wait five minutes or four hundred microts. Using this, one microt would be 0.75 seconds.
  • In The Flash (2014), Barry Allen discovers that he cannot get drunk anymore due to his new powers, even from a "500 proof" dose of alcohol. The problem? Proof is a measure of how much alcohol is in a beverage, and cutting it in half gives you the percentage. So, a 100-proof drink would is 50% alcohol. This means that pure alcohol would still only be 200-proof and that a 500-proof drink is nonsensical and impossible to create by definition (as it'd have to contain 250% alcohol).
  • In the documentary Forensic Files on TruTv, it is stated that a gunshot produced 120 decibels of sound, and that 70 decibels, or "about 60%" of that, went through to an adjacent room. The decibel scale is logarithmic, with 20 dB being equivalent to a factor of 10 increase in (Pa) amplitude, so 70 dB is really about 0.3% of 120 dB measuring by the raw pressure function.
    • For comparison, 120 dB is just short of the pain threshold, about as loud as sitting in the front row at a rock concert or using a power saw. 70 dB is a little louder than a normal speaking voice. For the sound of a gunshot heard through a wall, the 60% figure seems accurate; the 70 dB not so much.
  • Defied in many episodes of Good Eats, where Alton Brown instructs his viewers to measure out X ounces of a dry good by weight. The emphasis on weight has two purposes: first, weight is generally a more precise indication than volume; second (and more relevant to this trope), it's so that viewers don't try measuring by volume (i.e. in fluid ounces).
  • Kaamelott: Arthur once told Perceval and Karadoc that a good sword stance involved facing the foe and turning 30 degrees. Perceval and Karadoc, naturally, decided this involved ice cubes.
  • Kamen Rider Fourze acknowledges the light-year issue in episode 12, when space Otaku Yuuki meets the school's chairman, a former astronaut. She says she's read his book "for light-years" and he immediately responds "Incorrect, light-years are a measure of distance". Rather than a mistake, however, it seems that Yuuki said this on purpose as a pretext to quote more of his book.
  • The episode "Getting Barry Higher In The World" of Last of the Summer Wine features Seymour enlisting Wesley to build them a kite, but Wesley assumes that because Seymour's a pompous schoolteacher with a university education, all the figures on his plan are in metres rather than feet. The kite comes out over three times too large, but when it turns out to work as a hang-glider, Seymour claims I Meant to Do That.
  • The plot of one episode of The Middleman revolves around "4000 angstroms of Balthorium-G"; an angstrom is a unit of length, not mass or volume. Word of God is that the writers were perfectly aware of this, but did it anyway because they thought it sounded better.
    • Better yet the angstrom is equal to a tenth of a nanometre and is used because its about the diameter of an atom. So 4000 angstroms is only 0.4 micrometres, or less than a bacterium (which are between 1 and 10 microns) long.
  • Even MythBusters made the "watts" mistake, displaying a chart showing the power consumption of light bulbs in "watts per hour".
  • In one episode of NUMB3RS involving a train wreck, Charlie maps out an extremely precise route for the agents to take to rescue trapped survivors, but when Colby attempts it, he gets stuck at a dead end. When Colby then repeats the directions back to Charlie, Charlie realizes what's missing.
    Colby: I did exactly what you said. Nine straight in, six left 30 degrees, seven right 15 degrees.
    Charlie: (realizing) Colby, are you counting in meters?
    Colby: (sighs) That's the problem. I'm counting in yards.
  • Chloe Sullivan also does this a couple of times in Smallville. For instance (in the context of a discussion involving time travel):
    Clark: You're saying Kara's actually on Krypton.
    Chloe: Well, Krypton 1989. Give or take a few light-years.
    • That makes it sound like she may or may not have been left drifting in deep space. Unfortunate implications, indeed!
  • An episode of Saturday Night Live hosted by Kelsey Grammer highlighted the confusion pointed out above regarding 20,000 Leagues Under the Sea. Nemo calmly explains that he misspoke and he should have used fathoms to indicate depth. However, the other characters (even The Professor) end up describing every unit of measurement, even time, in terms of leagues, leading to Nemo being brought to the edge of madness before being dragged away by a giant squid.
    Narrator: The entire crew of the Nautilus — all 20,000 leagues of them — searched for Captain Nemo for over 20,000 leagues and nights. 20,000 leagues later, they still hadn't found a trace of Captain Nemo, the man they called.. Ol' 20,000 Leagues Under The Sea!
    Captain Nemo: Noooooooo!!!!
  • In an episode of the Australian series Ship to Shore, a report (later revealed to be false) came in of a tsunami 30 feet (10 metres) high came in. Since some of the older islanders still used imperial units, the confusion snowballed to the point that the wave was supposedly 900 metres (3000 feet) high, and the islanders prepared for Armageddon.
  • At one point in Stargate SG-1, the team is in a rapidly-cooling room and needs to find a source of heat. Carter informs everyone that they just "passed –40 degrees". Jackson asks if that's Fahrenheit or Celsius, and Mitchell responds that it doesn't matter: the two scales are the same at that point.
  • Star Trek:
    • Several Star Trek episodes have used the word "teradyne" as a unit of computer processing power. "Dyne" in the Trek universe seems to mean "a small amount of whatever it is we're talking about right now." Additionally, an episode of Star Trek: Voyager gave the power output of the warp core in "teradynes per second". Dynes are a unit of force, not energy.
    • The Voyager writers had trouble even keeping their own fictional units straight. On at least one occasion, "cochranes" were used (quite incorrectly) as a measure of explosive yield, rather than the proper usage as a measure of warp field strength.
    • The term "iso" has been added to both tons and rems (a measure of radiation). Iso means "equal" or "homogenous", suggesting that it's either meaningless (e.g. 6,000 isorems means 6,000 rems), some weird "equivalent to that much as far as we're concerned" shorthand taking into account bizarre Star Trek science or, as the term is often used when someone's explaining how screwed they are, means "It's 6,000 fucking rems out there!"
    • And then there's the Royal Brat from "Elann of Troyus" who joins the ranks of those who think that "light-year" measures time instead of distance. Then again, considering that she is a snob who's disdainful of anything STEM-related, that may have been intentional on the part of the writers.
    • Star Trek: The Next Generation:
  • Top Gear has a tendency to parody this.
    • James May, being Good with Numbers, gives accurate conversions but refers to metric and imperial respectively as 'Roman Catholic' and 'Church of England'. Jeremy Clarkson on the other hand deadpans complete nonsense such as measuring torque by spreading his hands apart and saying 'about that much'.
    • Another thing Jezza was fond of doing was using "torque" without specifying what unit (pound feet, newton metres, etc) he was giving the torque figure in, and instead treating the word "torque" as a unit of measurement in and of itself. He would also pluralise the word "torque". "This new supercharged doodad has over 500 torques!" Played for Laughs, obviously.
  • In The Goes Wrong Show, in the episode "A Trial To Watch", some setpieces of a play are designed in inches, but the set engineers misread them as being in centimetres. Hilarity Ensues.



  • For their 1983-84 Born Again tour, Black Sabbath had planned to have several Stonehenge-like monuments onstage. Unfortunately, the monuments were built 15 meters in height (rather than the intended 15 feet), meaning each one was almost 50 feet high. This inspired the "Stonehenge" scene in This is Spın̈al Tap, where the problem was inverted.
  • The Chris de Burgh song "A Spaceman Came Traveling" (a sci-fi interpretation of the first Christmas) explicitly refers to "light-years of time"; the writer not only makes the mistake but goes out of his way to wave it in the listener's face.
  • The Sparklehorse album Dreamt for Light Years in the Belly of a Mountain. Perhaps the mountain was hurtling through space.


  • In the folk song "The Frozen Logger", the title character freezes to death when the temperature reaches "a thousand degrees below zero"; though no units of temperature are specified, there are no commonly used units that go that low. As the song is a Paul Bunyan-esque tall tale, this is entirely appropriate to its tone.

  • One of the many possible definitions of the diagonal in Mornington Crescent (specifically Archbald's Metropolitan Logorhythmic Progression) states "the diagonal shall be agreed to be any angle being agreed to be an angle between the angle of one degree and the angle of three hundred and fifty nine degrees ... Celsius".

    Tabletop Games 
  • As a "watts" example in reverse, GURPS sourcebooks insists on referring to kilojoules as "kilowatt-seconds". Although technically correct this is inelegant and confusing and proof that, even with the constant calls for them to abandon Imperial units, Steve Jackson Games shouldn't be let loose with SI.
    • They can't even keep that much straight. Centimeters get used from time to time, generally for weapons. More confusingly the abbreviation mps is used to talk about mile per second despite the fact that even people in the US think of it as metres per second.
      • That bit Steve Jackson at least gets correct. The abbreviation for metres per second is m/s or ms-1.
    • In at least one GURPS Traveller supplement, there's an extended sidebar on the difference between short tons, long tons, metric tons, water-displacement tons, and liquid hydrogen-displacement tons, all of which have some relevance in the setting. (A "100-ton ship", in Traveller, has a volume equal to 100 metric tons of LH2.)

  • Les Luthiers has a temperature-related example in "Radio Tertulia", when Ramírez is stating the temperature and Murena has no idea what Farenheit is:
    Ramírez: The temperature is 27 Celsius degrees, 80 Farenheit degrees.
    Murena: 80 degrees... it's really hot!
    Ramírez: It's the temperature in Farenheit.
    Murena: Ah... right, now that you say it, it did sound like it was too hot... okay, right, it's the temperature in Farenheit.
    Ramírez: Right.
    Murena: But, tell me... what's that? Somewhere in Africa?
    Ramírez: Farenheit is the name of the physicist that invented that temperature scale.
    Murena: Ah, that's okay, right. We can call him Doctor Farenheit.
    Ramírez: Yes.
    Murena: But still, I have to tell you. He has a really bad fever!
    Ramírez: (Beat) Yes, Murena, he has a fever.
Murena: Why not? 80 degrees... is a fever.

    Video Games 
  • The manual for Fallout, written from an In-Universe perspective from Vault-Tec (the company which made the vaults), suffers from several mistakes in one unit when it gives the technical specifications for Vault 13. Among them is: "Power requirements.....3.98mkw/day". Even assuming that the w is supposed to mean Watts (which have the symbol W, being named after a person) and ignoring the pointless prefixes which seem to cancel each other out (m would mean times 1/1000 while k means times 1000), Watts are already a unit of power, so the "per day" part is redundant. Justified somewhat in that Vault-Tec is portrayed throughout the manual as tending to cut corners and not being very knowledgeable about what they're doing.
  • Ghost Trick: In the ending, Beauty and Dandy are breaking into a safe above Chicken Kitchen with gunpowder. Dandy reads the instructions for twenty kilograms of gunpowder instead of twenty grams.
  • Metroid Prime 2: Echoes: The game manages to do this with its fictional measurement of time, the cycle. While the length of one cycle is never really stated, based on its use in the Space Pirate logbooks it would seem to be analogous to something between a few months and a year. However the Luminoth elder U'mos is described as being several centicycles old. They probably meant several hundred cycles, but the prefic centi means one-hundredth. Presumably the writers either weren't aware of the correct prefix, or just decided it sounded cooler than "hectocycle".
  • No More Heroes: An infamous example occurs in the lawnmowing minigame, where "square meter" has been culturally "translated" into "acre" (roughly four thousand square metres).
  • OutRun 2019, depending on the regional version. In the Japanese version, your top speed in manual transmission (which gives a slightly higher top speed than automatic) is 341 kilometers per hour. While perhaps the most realistic speed, you'd expect a rocket-powered car in a 90's depiction of 2019 to go much faster, especially since other racing games by Sega have you reaching that speed in far more realistic cars, like in Virtua Racing, Daytona USA, and even other OutRun games where you're just driving a Ferrari (or a copyright-friendly substitute). The North American version has your top speed at 692 miles per hour, which sounds cooler although you don't seem to be moving that fast (for reference, common passenger jet aircraft move at about 500 mph). The European version has perhaps the most plausible speeds, listing your top speed as 341 mph. But perhaps the most important issue is that none of these units convert correctly to one another: 692 mph would convert to 1,113 km/h, 341 km/h would convert to 211 mph, and 341 mph would convert to 548 mph.
  • Pokémon Red and Blue (as well as their remakes, FireRed and LeafGreen) referenced the light-year mistake with the Junior Trainer (Camper in the remakes) in Brock's gym, saying you're "light-years from facing Brock", but then acknowledging the mistake after you beat him.
  • The ZX Spectrum game Road Race betrays its roots as a lazy port of the MSX Hyper Rally with its speedometer, swapped from km/h to mph with no attempt to recalculate and leaving the 374 mph top speed feeling very sluggish indeed.
  • Terranigma incorrectly exaggerates the age of the Earth in its opening, due to the "Blind Idiot" Translation of "46 okunen"note  as "46 billion years." (4.6 billion, of course, is the correct number.)
  • The English dub of Valkyria Chronicles does this with military units by mistranslating shotai as "squad" instead of "platoon"—the latter being the correct size for the army unit depicted as well as the appropriate unit to be commanded by a lieutenant.

    Web Animation 
  • Parodied in Star Wreck, where the twist in the maggothole (sic) is stated to be several mega-parsec-seconds in the Finnish original, and googol-fluxoms in English translation. Naturally, neither of those make any sense.

  • In the Darths & Droids take on the "twelve parsecs" line, the real Han Solo (the film's Greedo) tells Jim's character "It did the Kessel run in less than three standard days. That's twelve parsecs, kiddo", meaning that this is how long the Kessel run is. When Jim's character steals Han's identity, he completely misremembers this. When called on it, he switches to light years. (And, bizarrely, gets the conversion right.)
  • In Girl Genius, a veteran airman breaks out an old mnemonic when his airship is attacked by a swarm of fiery robots: "If you'd live to end of day, from Mechanicsburg two leagues stay." The helmsman demands to know whose leagues, and what that works out to in kilometers to which the airman replies he has no idea as everyone gave it a berth wider than two of anyone's leagues. As it happens, the robots' master specifies they should chase their target for ten kilometers, which is near enough to 2 English leagues, or 6 miles.
  • In Homestuck, Terezi claims to be 6 in her first conversation with Dave, who is kind of shocked. Though, at this point of the story, the reader is aware that Alternian Solar Sweeps are longer than Earth years. To clarify, trolls are about the same age as the kids (13 years).
  • Early Schlock Mercenary strips have a nasty habit of referring to "watts of energy." Even as late as the third book, while it gets right that terawatt-nanoseconds would be a unit of energy (one more commonly known as the "kilojoule"), it treats it as though nanoseconds make it more incomprehensibly huge than "terawatt-hours" or, say, "terawatt-millennia."
    • It also plays with this trope with some things, such as freem, which are explained as the amount of pay a "Poliflorian Hypernetter earns about two thousand Freem during one Efrickalian work-week."
  • In Sequential Art squirrels try to build giant robots to fight a giant bug and forgot to agree if they are using millimeters or centimeters. But they like the resulting battle armor even better.
  • This xkcd has a character become confused about whether to give a temperature in Fahrenheit or Celsius and use radians, a measure of angle, instead.

    Web Original 
  • Hadriex tried to convert the vague system Heroes of Might and Magic 3 uses to count enemy units into something he could wrap his head around. Like Metric. It didn't work out so well.
  • Happens in an SCP Foundation story "Units". There is a big difference between mA and MA, resulting in SCP-9017's escape. Blake didn't realize he has set the containment field circuit to nine orders of magnitude lower than normal because he didn't think it mattered.

    Western Animation 
  • In one episode of Ed, Edd n Eddy, Edd is working on an old radio, and realizes he'd mistaken a "fifteen-amp resistor" for another part. The problem is, amps are used to measure current, and the ohm is used to measure resistance. Resistors have power handling specifications too, but the unit for those is the watt, so that doesn't help.
  • In the Family Guy Star Wars episode "Blue Harvest", Han Solo (Peter Griffin) claimed that the Millennium Falcon completed the Kessel Run in less than 12 parsecs. Luke (Chris Griffin) then tells an astonished Han that parsecs are a measure of distance, not time.
  • Professor Farnsworth once claims that 1 pound of dark matter weighs as much as 10,000 pounds of normal matter. Pounds are units of weight, not volume: a pound of feathers weighs exactly the same as a pound of brick, it just takes up more space. Probably a Parodied Trope, though, given this is Futurama we're talking about.
  • In the episode of Hey Arnold! where they try to get into the world record book, their attempt at the largest pizza pocket fails when Sid misinterprets "tsp" for the yeast requirement as "ten square pounds" instead of "teaspoons".
  • The protagonist of the children's cartoon Jimbo is a talking Jumbo-jet that was manufactured in centimetres instead of inches by mistake.
  • In Johnny Test, the girls have used Newtons as a unit for magnetic force. While technically correct, Teslas would have been a much better unit, because they measure the strength of the field. The force also varies with the velocity of the charged particle.
  • The Simpsons:
    • Crazy Vaclav asserts that the car he's trying to sell will "do 300 hectares on a single tank of kerosene". The hectare is a measure of area, not distance. Can be justified by the fact that Eastern European cars would be used for agricultural purposes and buyers would want to know how much of their fields they could cover per unit of fuel.note 
    • Grampa Simpson hates the metric system. "My car gets forty rods to the hogshead, and that's the way I likes it!" note 
    • Mr. Burns has trouble with metric too, like in the episode he drops a weight marked "1000 grams" (just over 2 lbs) on Homer, to his minor annoyance, and then comments that it sounded much heavier when he ordered it.
    • In the episode where Bart goes to a gifted school, the kids con him out of his lunch by using units like picolitres to make it sound like they were offering more than they were.
    • In the beginning in one episode where Homer takes the kids to school, he uses a GPS which gives him the distances in meters. The confusion leads him through a construction zone.
    • From one of the Halloween episodes:
      Kang: This is the best play in light-years.
      Kodos: Light-years measure distance, not time.
      Kang: You know what I meant.
  • In an episode of Spider-Man: The Animated Series Spider-Man specifies a frequency in microfarads. Frequency is normally measured in hertz whereas the farad is a unit of electrical capacitance. The fact that Spider-Man was smart enough to be able to guess the correct frequency for the Techno Babble that he was trying to pull off should have made this mistake unthinkable.
  • Steven Universe: In "Chille Tid", an exhausted Pearl at one point mistakenly says they've been "searching for light-years" for Malachite/Lapis Lazuli and Jasper. An equally-exhausted Amethyst sort-of corrects her by replying "light-years measure light, not years".
  • In Transformers, (well, some series, anyway) "light-year" has been a unit of time.
    • Transformers has more units of time and distance than you can shake an exhaust pipe at. Most of them have never been explicitly defined, so any of them could be this trope.
  • Voltron: Legendary Defender: Besides Earth, the entire universe uses Altean units of measurement (presumably enforced by the Galra Empire). The human characters get used to using them pretty quickly, but we're never given an explanation for any of them except for the tick, which is slightly longer than an Earth second. This lets the show keep things like time and distance vague while making the characters sound like they know what they're talking about.

    Real Life 
  • The Metric system is an intentional aversion of this trope. It was intended to become an international, independent and accurate system based on natural phenomena and constant, and be base-10, and be useful on both everyday use and for science. Justified, since there were some 38 different pounds and 43 different size feet in France alone - which were a constant source for Unit Confusion, chaos and outright fraud. Several buildings and bridges collapsed because the masters and builders from different towns and different provinces used their own domestic, different size, units in construction — cue the case of the 17th century Swedish warship Wasa which is lengthwise asymmetric because of port side having been built by Swedish constructors using the Swedish feet (297 mm) while the starboard side having been built by Dutch constructors using the Dutch foot of 283 mm. To add an insult to injury, the Dutch foot consisted of eleven inches. This unit chaos originated in the fall of the Western Roman Empire and collapse of standard weighs and measures. Alas, every petty kingdom, statelet and town adopted their own weighs and measures to emphasize their independence. Already Charlemagne had attempted to make some sense in this chaos, but the various realms clung jealously on their own weighs and measures and would not approve standardization. The various scientists of the Age Of Reason - Newton, Huygens, Bernoulli, Papin etc - worked for an international standard system for weighs and measures, and the work was ready in 1790. King Louis XVI approved the Metric system legal in France.
    • UK and USA have clung on their pre-Metric unit systems, and pretty well standardized their weighs and measures. But there is still a risk of confusion between the UK gallon (4.54 litres) and US gallon (3.78 litres) and the corresponding liquid measures. The US pint is 478 ml and consists of 16 US liquid ounces, while the UK pint is 568 ml and consists of 20 UK liquid ounces. Hence the proverb "Pint's a pound the world around" as one US pint of water weigh almost the same as pound avoirdupois (454 g).
    • There are still no less than six ounces still in use: avoirdupois ounce, troy ounce, US liquid ounce, US dry ounce, UK liquid ounce and UK dry ounce. Two first are units of weight, while the rest four are those of volume.
    • Short hundredweight (100 lb) and short ton (2000 lb) versus the long hundredweight (112 lb) and the long ton (2240 lb). The 'short' weights are used commonly in the USA, while the 'long' weights are used in the UK.
    • The US has the "statute mile" (1609.344 metres), the "geographical mile" (1853.245 metres) (not to be confused with the "nautical mile", which is only 1852m) and the "survey mile" (1609.347 metres, and also known as the "U.S. statute mile").
  • In Real Life, the results of metric confusion can be catastrophic and very expensive, as when the Mars Climate Orbiter crashed and was destroyed in 1999 — the "small impulse" analysis software was giving data in pound-seconds, while the mission navigation team was expecting data in Newton-seconds.
  • During World War II, a mission to supply Malta by airplanes taking off from an aircraft carrier ran into grief because the Royal Air Force (which supplied the airplanes) thought that the distance they would have to fly was in statute miles. But the distance had been given to them by the Royal Navy, which of course used nautical miles (1 nautical mile = 1.151 statute miles).
  • This was also used fraudulently by 19th-century colonists in South-West Africa (modern Namibia) who purchased land up to a distance of so and so many miles inland from the coast from local tribes. What they did not mention in the negotiations, but wrote down in the contracts was that the distance specified was not in the British statute miles (1 mile = 1.6 km) familiar to the tribal leaders through contacts with e. g. South Africa, but used the less familiar geographical or German mile (ca. 7.5 km).
  • A more down-to-Earth example (no pun intended) was the Gimli Glider. The Boeing 767 C-GAUN was the first Air Canada jet with metric instrumentation. There already had to be a measurement conversion because the refueling people on the ground measured kerosene in volume (gallons), while the aircraft measured fuel in weight (pounds or kilograms). The ground crew used the wrong conversion factor in calculating how many gallons to pump on the plane, leading the crew to think the plane had 22,000 kilograms of fuel on board, the amount needed for the flight, when it only had 22,000 pounds (9979 kg). The exact mass of fuel used is very important to aircraft and thus the gauge could not be replaced with a car style unitless gauge. Nobody on the groundcrew or in the cockpit had been trained to do the proper conversion; this kind of thing used to be the job of the flight engineer, but computerized jets like the Boeing 767 have eliminated the need for that position, and apparently no one at Air Canada had stopped to consider who should take over the FE's duties.
    • There was an extreme level of luck involved in the flight having no fatalities. The captain happened to be a glider pilot (and thus knew about the unique requirements of powerless flight) and the first officer happened to be a former RCAF pilot who was stationed at RCAF Gimli, a nearby (decommissioned) airbase. The base had been converted into a race track and the pilots managed not to hit the drag races held on the runway they landed on, so nobody got hurt both on plane and on the ground. Note that in later simulator re-creations of the circumstances with other flight crews, every one ended with a fatal crash.
    • Under normal circumstances, the fuel gauges would detect the actual amount of fuel loaded and that would prevent the problem. However, the fuel gauges were broken on that particular plane, which they actually knew, but this was not considered a serious enough fault to ground the plane.note  Without the gauges, the pilots depended on the FMC's calculated fuel weights to track fuel consumption during the flight, but because it had been given an incorrect starting weight, all its calculations were based on that and therefore also wrong.
  • A fatal example of this trope occurred with Korean Air Cargo Flight 6316. As the plane was climbing, ATC cleared the flight to 1,500 metres (4,900 feet). The flight crew misinterpreted this order as 1,500 feet, leading them to believe they were too high. The captain attempted to descend, but pushed the control column too hard, causing the plane to nosedive into a neighborhood, killing all three crew members and five people on the ground.
  • During World War II the American-made Packard Merlin spare parts would not fit on British made Rolls-Royce Merlin engines and vice versa. That was because the American and British inch differed from each other by 2 millionths (roughly 0.5 micrometers). That does not sound much, but on precision engineering it is. If a Rolls-Royce Merlin was supplied with Packard spares, it would sprinkle oil, and if a Packard Merlin was supplied with Rolls-Royce spares, it would seize up. That led in plane type re-designations by Royal Air Force; Spitfire Mk. IX and Spitfire Mk. XVI were basically the same plane, but Mk. IX had Rolls-Royce Merlin engine while Mk. XVI had Packard Merlin engine, so that the airplane mechanics would not confuse Rolls-Royce and Packard spares on wrong engines.
  • Packaging frequently treats "net weight" and "net mass" as interchangeable, even though weight (meaning the force of the object being pulled down) and mass are different quantities. According to NIST handbooks, "weight" is to be treated as referring to mass in such contexts.
    • That's because the mass-to-weight ratio is a constant on Earth (or close enough: on average g = 9.81 m/s2 or 32.2 ft/s2) meaning there is a linear correlation between mass and weight. On Earth it pretty much means the same thing then. However, move to environments with a different gravity (basically any other planet or moon, although the correlation will be linear on that world) or even space (where weight becomes meaningless) and you get a different story. Even worse: if you launch the object from a planet and into space, the gravity exerted on the ship becomes variable (inverse square law) meaning the correlation between mass and weight is no longer linear.
      • It's more complicated than that. The acceleration due to gravity on the Earth's surface varies from place to place enough that, for a spring/piezo scale (that measures the pressure on its surface and from that infers a weight and thence a mass), the results cannot be trusted to more than two significant figures unless the scales have been locally calibrated. (This does not apply to balance scales which compare the mass being measured against a supplied known mass.)
  • The pound is both a unit of weight and a unit of mass. In some engineering contexts the pound is used exclusively to refer to weight, even though legally the pound is defined as a mass unit.
    • In scientific literature, you may find references to the "pound-mass" to refer to that concept, abbreviated "lbm", mainly because the Imperial unit of mass, the slug, is stupid. Whether that particular convention is followed or not, though, is hit or miss. The definition of slug is "the mass which accelerates by 1 ft/s2 when a force of one pound (lbF) is exerted on it." One slug has thus a mass of 32.174049 lbm or 14.593903 kg based on standard gravity, the international foot, and the avoirdupois pound. At the surface of the Earth, an object with a mass of 1 slug exerts a force of approximately 32.2 lbF or 143 N.
    • Made even more confusing since sometimes "lbf" is used for "pound-force", so sometimes you'll have "lb" (pound-force) and "lbm" (pound-mass), or "lb" (pound-mass) and "lbf" (pound-force) used in text. Best to just always stick with "lbf" and "lbm" and eliminate confusion.
    • Even more confusing is the concept of poundal, which is force. The poundal (symbol: pdl) is a unit of force that is part of the foot–pound–second system of units, in Imperial units introduced in 1877, and is from the specialized subsystem of English absolute (a coherent system). 1 pdl = 1 lbm⋅ft/s^2 The poundal is defined as the force necessary to accelerate 1 pound-mass to 1 foot per second per second. 1 pdl = 0.138254954376 N exactly.
    • Of course serious modern scientific literature should use the SI or units which are typically used in the field.
    • The unit of weight (normal force) in the SI system is newton (N). One newton is one kilogram (mass) multiplied by 1 m/s^2, making a mass of 1 kg weigh 9.81 N on Earth. The value 9.81 is close enough for 10, making conversions easy - just multiply by ten.
    • The units of energy (distance multiplied by force) and torque (distance multiplied by force), but they are different products. Energy is scalar product while torque is cross product (vector product). Thus while the unit of both are newtonmetre in SI system, the unit of energy has its own name, joule (J): 1 J = 1 Nm. The unit of torque is newtonmetre, but cross-product (N×m). When you lift a weight of one newton up one metre, it is energy of one joule; when you pivot a lever, length of one metre, by force of one newton, it is torque of one newtonmetre).
  • Precious metals are measured in troy pounds (373 g), which are divided into 12 troy ounces (31 g) — standard ("avoirdupois") pounds (454 g) are divided into 16 ounces (28 g). (Hence, an ounce of gold weighs more than an ounce of feathers, but a pound of gold weighs less than a pound of feathers.)
    • This video shows more examples of units with the same names but different values (e.g. short tons vs. long tons, statute miles vs. nautical miles vs. imperial nautical miles, etc.).
  • There's a story about a guy from Indonesia who got fired from a multinational company because he measured an ounce as 100 gramsnote  and a pound as 500 gramsnote , which resulted in years of equipment malfunctions. It turned out that such units were once used in the Netherlands (called ons and pond), and although they're not formally used anymore today, the guy's home country, that is a former Dutch colony, keeps teaching it at schools.
    • This is because at the time the metric system was introduced into the Netherlands (in the 19th century), the ons and pond were the Dutch equivalents of the English ounce and pound, with approximately the same weights. They were redefined in metric terms to ease the transition, but unlike some other such measures never really fell out of use, though they really only get used for day-to-day measuring. Even today, many people ask for things like "an ounce of minced meat" when they want 100 grams. Very, very few of them will know that such an ounce was not always 100 grams — including translators, who often translate the English word "ounce" with either "ons" or "100 grams", making the quantity over three times as big at a stroke. Oh yeah, and don't even try finding a translator who knows how big a fluid ounce is.
      • Cases similar to the Dutch case can be seen in Greater China as well. Traditionally , 1 catty = 16 taels =160 mace = ~600g. In 1959, however, Communists introduced a similar transition scheme, where 1 catty = 10 taels = 100 maces = 500g. Of course, the jurisdictions that are not under direct Beijing control—Hong Kong, Macau and Taiwan didn't follow. This is particularly confusing as these Chinese units of measurements are still in common use for foodstuff and precious metals..
  • At least in Germany, instead of saying "kilometre per hour", many people tend to use the abbreviation "kmh" in everyday conversation. But only the letters are said out loud, not the slash. If this unit wasn't so ubiquitous, you could easily mistake this for "kilometre multiplied by hour".
    • Some also still use the vernacular expression "Stundenkilometer", which could be misinterpreted as "hours multiplied by kilometres", but translates more closely to "hourly kilometers".
  • At least in Canada, people will sometimes use (or at least recognize) the military slang "klicks" as an abbreviation for "kilometre" and also use it as an abbreviation for "kmh", meaning there's a difference between "I have to go 20 klicks" and "I have to go at 20 klicks."
  • In 2004, Switzerland and Germany wanted to build a bridge over the Rhine, starting from both sides. To meet in the middle, they agreed to build it on a certain height above mean sea level. Unfortunately, the Germans measured in height above the North Sea, while the Swiss measured in height above the Mediterranean Sea, which differ by about 27 centimetres. The designers were aware of that difference, but the Swiss applied it the wrong way, building their abutment 54 cm too low. This was discovered relatively early, the plans modified and the situation of this old cell phone ad was avoided.
  • Although technically supplanted by the SI measurement of energy in joules, "calories" is still widely used to quantify the energy contained in foodstuffs. Rather, it's misused by any chemist's standard, as a "calorie" in chemistry is sufficient to heat one gram of water by one degree Celsius, whereas one "nutritional calorie" is sufficient energy to heat one kilogram of water that much, i.e. a kilocalorie. Seems it's harder to sell diet foods if your packaging lists their energy-content as "Just 10,000 calories!" instead of "Just 10".... However, this is averted in several countries, which correctly label food with kilocalories (or kilojoules), which can result in panics from visitors from countries who don't do this.
  • One example of unit conversion confusion comes from a puzzle on this page, which talks about a peculiar instruction on a page of a recipe cookbook that was originally written using the Celsius scale and was translated to use Fahrenheit: "If your oven has a fan, reduce the recipe temperature by 68°F." Because the zero points of the Celsius and Fahrenheit scales are different, converting between differences in temperature is different than converting between the temperatures themselves, and the difference of 20°C (36°F) in the original recipe book becomes a little over 37­°C when "converted" in this way.
  • For many years, computer memory units used prefixes that looked like SI prefixes, but were subtly different. The Kilobyte was 1024 bytes, for example. This all went horribly wrong one day when an enterprising Marketer realised they could sell harddrives with storage capacities measured in megabytes... but using the SI meaning of mega (106), not the computer engineering meaning of mega (220). Result? Sell smaller drives, but claim the same size, thus undercutting competitors who spent more to make bigger drives because so many consumers didn't stop to check the difference. As a result of all this, a so-called "1.44 MB" floppy disk is neither 1.44 binary megabytes nor 1.44 decimal megabytes, but 1.44 thousand binary kilobytes. There are now new standard prefixes like 'kibi' and 'mebi' (short for kilo-binary and mega-binary, respectively) to mean 1024 and 1048576 respectively, but they've so far failed to be embraced by the hardware and software community outside of hard drive manufacturers (with the exception of Linux, which does use the binary units and prefixes). Plenty of consumers notice the difference when they buy a new laptop, and return it to the store complaining they've been short changed because they were sold a machine with a 720 gigabyte drive but they're only seeing 670 (because it's 720×1000×1000×1000 bytes according to the marketers, but divided down in 1024s by the OS).
  • Data bandwidth, whether from a network or local peripheral bus (like USB) express speed in raw data rates, not usable data rates. And it will always use bits per second (using a lowercase b) and not bytes per second (using a capital B).
    • For example, the hard drive bus SATA has a raw data rate of 6 gigabits per second. But it uses 8/10b encoding (where 8 bits are padded to 10), making 20% of the bandwidth unusable. Then there's SATA protocol overhead. After all that, the maximum data rate is about 4.4 gigabits per second or about 550 megabytes per second, the ceiling of performance SSDs can achieve.
    • There is, perhaps, a technical reason for this. When talking about how much a transmitter can change from one distinct value to another, the actual term is called baudnote . But since its a term not commonly spoken, "bits per second" is used in this context instead. However, some transmitters for the sake of signal integrity use more bits to transmit the actual data. A common example is 8b/10b encoding where 10 bits are used to transmit 8 bits of data. But before you go "couldn't they just take out the encoding overhead?", a byte isn't always 8-bits.
  • Napoléon Bonaparte was five foot two in pre-metric French units, but five foot six in British units (about 168 cm). This means he was not quite as short as his popular stereotype.
  • Subverted by relativity. If time is just another dimension the same as the other three, then you can perfectly well use the same units for each - and indeed this is extremely useful, meaning amongst other things that speed is a unitless quantity. You convert using the speed of light, that being a fundamental constant (with the consequence that relativistic physics only rarely uses c to represent the speed of light, because its value is simply 1). This means that, though not a particularly useful unit, a 'light-year of time' is not, in fact, meaningless. Rather charmingly, it is precisely the amount of time it takes light to travel the distance light can travel in a year.
  • Following on from relativity, several "natural units" systems (de Sitter, Gaussian, Planck, and Stony to name a few) have been developed by physicists. By making a judicious choice of physical constants and interpreting them as conversion factors (such as using the speed of light to convert between length and duration) physical quantities in any units can be made interconvertable. The constants themselves all end up being equal to 1.
  • The shoe sizes are a complete quagmire. Not only do the shoe sizes depend of the country and culture, but also whether they are based on the foot size or last size (a last is the male "mould" upon which the shoe is made). The most common units are Mondopoint (foot length and beam in millimetres, used on ski boots and by US armed forces), the EU sizing (1.5 times the length of the last in centimetres), US male shoe size (3 times the last length in inches minus 24), US female shoe size (3 times the last length in inches minus 22.5) and UK shoe size (approx 3 times the heel to toe length in inches minus 23). The UK sizes are one barleycorn (1/3 in or 8.47 mm) apart each other, while the EU sizes are 2/3 cm (6.6667 mm or 0.262 in). Mondopoint shoes are sized 5 mm apart, and they also take account the beam of the foot: 275/100 shoe is, while of same length (275 mm), 10 mm narrower than 275/110.
  • There have been cases of motorists being pulled over by traffic cops for speeding, and giving the excuse that they confused miles per hour with kilometres per hour.
  • Quite a bit of old Russian literature can be confusing to the modern reader due to the once popularity of the Réaumur scale there (water freezing at 0 and boiling at 80). It's simple enough to convert to Celsius; just multiply by four-fifths.
  • This is likely why building trades in metric countries like Japan and English-speaking Canada often continue using traditional measurements even after metrication, as a conversion error in construction can be catastrophic.
  • In freight shipping, insurance costs have to be negotiated between buyer and seller (part of the so called Incoterms process); for Incoterms that explicitly address insurance, default coverage rates are calculated based on the number of "units" being shipped. It is vitally important to specify on consignment notes and bills of lading exactly what a unit is (e.g 10×36 cases vs. 10 pallets vs. 4320 bottles) or someone will be either woefully underinsured or the premiums would be more than the shipment is worth.
  • When the wreck of the 17th century Swedish warship Wasa was lifted from seabed and examined, it was found to be asymmetric lengthwise. The reason was that the port side was built under Swedish masters, who used the Swedish foot (12 Swedish inches, 292 mm) as the measure, but the starboard side was built under Dutch shipbuilding master Hendrik Hybertson, who used Dutch feet (283 mm). To add an insult to injury, the Dutch Amsterdam foot was divided into eleven inches, so one man's four inches was not the same as another man's four inches.
  • Another source of confusion is the fact that "ton" (2000 lb, or 907.2 kg) and "tonne" (1000 kg, or 2204.6 lb) are pronounced exactly the same; which one is being referred to may depend on where you are — the United States for the former, or pretty much anywhere else for the latter. This can be alleviated by referring to the former as "short ton" and the latter as "metric ton", or by agreeing beforehand which system you're using. (Oh, and there's also the "long ton" (2240 lb, or 1016 kg), just to keep things even more interesting.)
  • A sure-fire way to tell a landlubber from sailors and aviators is to ask the speed of the craft. A landlubber will tell it as knots per hour while a sailor or an aviator will tell it as knots. Knot is the correct expression - it is one nautical mile per hour. "Knots per hour" would be a unit of acceleration - close to 0.000143 m/s^2
  • The voyage that led Christopher Columbus to come across the Americas can be owed to this trope. When getting measures to calculate the circumference of the Earth, Columbus learned from Alfraganus that a degree of latitude spanned 56.67 miles, allowing Columbus to conclude that the Earth's circumference was around 30000 km (18641.136 miles) and that the East Indies (that is, China and Japan) were around 4400 km (2800 miles) away from the Canary Islands. What Columbus failed to notice, however, is that Alfraganus's calculations were using arabic miles instead of roman miles. Arabic miles are around 25% longer than the roman miles Columbus assumed the latitude length was measured on. Thus, Columbus's first expedition did not have enough supplies to survive a voyage that would take them more than he thought. That is, unless something else happened to be in-between...