The Metric System Is Here to Stay

"''"'Ark at 'im! Calls 'isself a barman and don't know what a pint is! Why, a pint's the 'alf of a quart, and there's four quarts to the gallon. 'Ave to teach you the A, B, C next." "Never heard of 'em," said the barman shortly. "Litre and half litre--that's all we serve. There's the glasses on the shelf in front of you.""

- Nineteen Eighty-Four

Although fiction set in the present-day United States tends to use imperial units, fiction set in the future is more likely to instead use the metric system. This may be because it makes things seem more futuristic: scientists use SI units (which is based on the metric system), and - given that most other countries, except Myanmar and Liberia, officially use the metric system - it may be only a matter of time until the United States also changes to metric.

While futuristic science fiction embraces this trope, futuristic fantasy often averts it: imperial measurements seem more appropriate for a non-scientific milieu.

The metric system is at least for scientific applications superior to the imperial system - water freezes at 0 degrees Celsius and boils at 100 degrees Celsius, and 1 Calorie is the energy required to increase the temperature of 1 liter (which is also 1 kilogram) of water by 1 degree Celsius. Thus, it's not surprising that the United States actually does use the metric system already, in military and scientific endeavors, as well as on pharmaceuticals and nutritional information. (For example, soft drinks commonly come in 2- or 3-liter bottles.) In fact, the United States' measurements (not imperial - that would be British, and there are differences, e.g. 1 imperial gallon equals 1.20095 U.S. liquid gallons) are defined in metric units in relevant legislation. Further details can be found on Wikipedia.

Just to note, the United States is one of only three countries, along with Burma (Myanmar) and Liberia, that have not adopted the SI (metric) as their official system. So it is generally considered only a matter of time.

Overlaps with Unit Confusion.

Anime & Manga

 * While Mobile Suit Gundam and its numerous spin-offs list all the Humongous Mecha specifications in metric units, it doesn't really qualify for this trope because the series is made in Japan, where the metric system is widely used. However, the fact that few (if any) American translations bother to convert them is probably due to this trope.

Film
"Wash: Start with the part where Jayne gets knocked out by a 90-pound girl, 'cause I don't think that's ever gettin' old."
 * Used as a joke in Zenon: Girl Of The Twenty First Century. Zenon is from a space station, but when she arrives on Earth, she explodes a test tube because she was thinking in Celsius when all the instructions were in Fahrenheit. In a science class.
 * Avatar, naturally. ("Klick" is military slang for kilometer, in case you were wondering.)
 * Also normal person slang in Canada.
 * Star Wars (though "inch" does appear occasionally in the Expanded Universe).
 * Technically, it's set in the distant past, but it is futuristic.
 * Like its originating series, Serenity quietly averts this trope with a single line:

Literature

 * Inverted by Scottish author Ken MacLeod's Fall Revolution books. When asked why spacecraft use imperial measures, Ellie May Ngwethru replies, "Fucking NASA." (Which is wrong; the reason the Mars Climate Orbiter crashed was that NASA and JPL were using metric but Lockheed-Martin was using imperial, and didn't check the measurements.)
 * NASA did use imperial units on the Apollo missions, though. Speeds were in feet per second, and distances were in feet or nautical miles.
 * Only on the displays. Internally, everything was stored and calculated with metric units, but the astronauts wanted altitudes and closing speeds displayed in American units.
 * Honorverse is thoroughly metric (even the Deep South of Grayson), to the point that Honor, while reading Oliver Twist in her spare time, wondered what those "inches" and "pounds" mean and how much would it be. Subverted when the Grayson pasttime of baseball is introduced in the books. Despite using metric for everything else, the Graysons stubbornly insist on using American measurements for baseball, because if they attempted to use metric, they'd either end up with crufty measurements (keeping the field the right dimensions) or end up with a field that was slightly off in distances. They refuse to update the game to include modern measurements because baseball is Serious Business.
 * But averted in Weber's Safehold Series. The people of Safehold use imperial units, which were deliberately imposed (along with roman numerals and certain religious proscriptions) early in the colonization project in order to hinder technological progress.
 * David Drake's RCN Series has Cinnabar use the imperial system while their enemies the Alliance (not The Alliance) use metric—but Drake says that's just Translation Convention because he believes that after more than a thousand years, humanity will have scrapped both systems in favor of something else.
 * As seen in the page quote, in British speculative fiction using the metric system in the future is usually a hint of dystopia. Oddly this is a much more common use than in American fiction, perhaps because the metric system has never been (in parts) imposed by government in America.
 * Thoroughly averted by Larry Niven. His Ringworld (for example) is "six hundred million miles" in circumference.
 * Uglies uses this, to the extent that another system of measurement isn't even mentioned.
 * Warhammer 40,000 novels use metric (but the game mechanics use imperial).
 * David Foster Wallace had a personal liking for metric (it seems), so in many of his works (including Infinite Jest), metric units prevail if he can help it.
 * There's a curious semi-inversion in the short-lived series of English translations of the Perry Rhodan novels. Because the originals are in German distances are given in metric, but translator Wendayne Ackerman consistently renders meters into yards - not even bothering to multiply by three to get feet.

Live Action TV
"Zoe: (referring to their attempt to dock at Niska's skyplex) It's like throwing a dart, Jayne, and trying to hit a bulls-eye 6,000 miles away."
 * Star Trek caused a scientific error due to this trope. During the production of the Star Trek: The Next Generation episode "The Royale", they "converted" a temperature to Celsius (presumably to make it more "futurey") by simply swapping the unit names. The original temperature was -291° Fahrenheit (-179,4 °C), but the lowest possible temperature (absolute zero) is -273.15 degrees Celsius... whoops.
 * Star Trek: The Original Series and its movies were known for using both the metric and imperial systems, sometimes in the same sentence, in a faintly baffling manner... much like the modern scientific community and US military.
 * The novelisation for Star Trek IV the Voyage Home featured Scotty having to mentally translate from metric to US customary when talking to the factory owner.
 * On Babylon 5, the eponymous station is consistently described as "five miles long". This is, however, the only measurement on the show that does not use the metric system.
 * Terra Nova. Justified in that there are people from several different countries in the settlement.
 * The Firefly episode "War Stories" showcases Wash's Improbable Piloting Skills, simultaneously averting this trope:

Tabletop Games

 * Traveller.
 * Champions. As of 6th Edition, all distances are in meters or kilometers. (Previous editions used "hexes" as a unit of distance or area, which were two meters across.)
 * Inverted in Steve Jackson Games' GURPS, which—despite the "Generic Universal" part of its name—has firmly stuck with the imperial system for the past twenty years, even when offering a licensed conversion of the Traveller system.
 * Apparently so much of the player base is American that they can't afford to switch to metric because, like many small RPG makers, SJGames is a margin business. (The Basic Set book does have a metric conversion table near the front.)
 * Also averted in Car Wars. Miles, feet, and pounds abound in Autoduel America.
 * Older versions of RuneQuest used metric for measurements.
 * Shadowrun and Cyber Punk 2020 both used metres for ranges and kilogrammes for encumberance purposes.
 * The 3rd edition rules for Star Wars d20 used metres, when literally all other games based on the d20 system were based on the imperial system.
 * Like the rest of its parent franchise, the Serenity RPG averts the trope, and more overtly than its predecessors. Speed is given in feet and miles, and warheads are measured in pounds, to name a few examples.

Video Games

 * F-Zero measures (ridiculously high) speed in kilometers per hour.
 * Halo. Mostly brought up in its Expanded Universe.
 * Whenever a waypoint was placed on your HUD, it always measures distance in either metres or kilometres.
 * The X-Universe series measures almost everything in metric. The only aversion is in time, for which the game uses Teladi-derived Standard Time Units (and as of X3: Terran Conflict, this has been scrapped for player convenience).

Webcomics

 * The (essentially) culturally American society shown in Schlock Mercenary uses the metric system, even among civilians... but every now and then the (American) author forgets himself.
 * Afterlife Blues. "You didn't recognise the Hero of Athens when you were two meters away from her?"
 * Freefall often has the characters using metric units with the Imperial equivalents in footnotes.
 * Escape from Terra, in addition the Martian calendar and system of time measurement is decimalized (1 Martian day = 100 centimes).

Web Original
"Mike: Alright, what you want to do here is take a right at the end of this road, and stay on it for about a mile. I mean, a kilometer or two."
 * Civil Protection implies that Earth's gone metric post-Combine-takeover when Mike gives directions in "Shadow of a Doubt":

Real Life

 * For some peculiar reason, British road signs still give distances in miles despite the fact that the metric system has been taught exclusively in schools since at least the early 1990s. Retailers exclusively use the metric system for all foodstuffs apart from beer and milk, which are defined in both systems.
 * The usual cited reason for not changing is the sheer expense of changing pretty much every roadsign in the land that has a number on it. Every distance sign and speed sign would need to be replaced, which would be a colossal undertaking. It's for the same reason that milk and beer can still be sold in pints; replacing all the pint bottles and glasses is not practical.
 * During The Eighties, a conclusive switch to the metric system was widely anticipated in the United States. Obviously, that didn't happen, but at the time the expectation was so prevalent that the newly-finished Interstate 19 put up signs with distances in kilometers. The program ran from 1975 to 1982, and it's worth noting that its failure was not necessarily because Americans disliked the metric system. Public opinion tended to be split or just ambivalent, so the Reagan administration couldn't justify the cost of overseeing and marketing the metrication effort, educating manufacturers, and changing highway signs. Several of the aforementioned metric road signs still stand today, particularly near the Canadian and Mexican borders.
 * The metric system did take hold in manufacturing, as companies wanted to build things that could be easily repaired overseas, hence Vanilla Ice singing about his "Five Oh" and not his "three oh two."
 * The expected switch to metric provided a lot of fodder for the Peanuts strip during this time, as seen here. The 1973 TV special There's No Time for Love, Charlie Brown has a Hilarious in Hindsight moment when Peppermint Patty says that, "We're going to have to learn the metric system, Franklin. By the time we grow up, the metric system will probably be official."
 * September 23, 1999: NASA lost the $125 million Mars Climate Orbiter because one engineering team used metric units while another used imperial units for a key spacecraft operation. The software keeping track of the small forces reported by the spacecraft's accelerometer gave results in pound-seconds of impulse, while the software that used this data to compute the spacecraft's course expected impulses in newton-seconds. The craft descended too low into the Martian atmosphere and was destroyed by atmospheric stresses and friction.
 * The US uses SI units for some things because no equivalent "traditional" units exist. For example, all electrical units are SI—watts, kilowatts, amperes, etc. The units of volume for sound (the bel and the more commonly used decibel) are SI as well.
 * Conversely, the metric system continues to use non-decimalized units for times greater than a second; partially because it would be a phenomenal pain to change on many levels, and partially because (unlike most units of measurement) the day and year are based on static phenomena and can't really be changed. However, it's not uncommon to do calculations involving X thousands of seconds, and convert it to familiar units of time at the end.
 * When the metric system was introduced in the United Kingdom, Punch did a satire which was purportedly a government information pamphlet that accompanied the switch from Biblical measures to Imperial (how many cubits in a yard?). Which was quite funny considering that there were people who wrote complex theories trying to justify the Imperial system, which differs quite significantly from the weights and measures used in the Bible, on religious grounds, demanding that it should be maintained against the "godless" Metric system.
 * The Gimli Glider had its share of problems on its most famous flight, but the one that mattered the most was that it had roughly 22,000 pounds of fuel aboard instead of the roughly 22,000 kilograms it needed. Only three things prevented a tragedy: a 767 can glide, the pilot knew how to fly a glider, and the co-pilot knew of a long enough runway that they could reach while gliding.