History UsefulNotes / AmericanCustomaryMeasurements

Car wheels (and inner dimensions of tires) are almost universally measured in inches. An abortive attempt was made to switch to metric in the early [[TheEighties '80s]]; as of the present, even Michelin, the driving force behind the move, no longer supplies tires to fit these sizes. Tire sizes are actually a complicated mix of units[[note]]the first number is in millimeters, the second a percentage (but may be millimeters), and the last in inches (but may also be millimeters. Fortunately, it's usually trivially obvious if the optional millimeter measurements are used, because the numbers will be much larger (around 2–3× as high for the second number, around ''25×'' as high for the last number).[[/note]], which is fine because almost nobody outside the automotive industry knows, much less cares, what they mean.

The metric system is also almost universally used by the scientific community, though UnitConfusion has sometimes arisen when American and international teams each assumed one was using the other's units. To further complicate matters, the American engineering community has held on to customary units, resulting in occasional disconnects between builders and users of scientific equipment (for example, the loss of the Mars Climate Orbiter, popularly attributed to UnitConfusion, was actually due in large part to this sort of thing, specifically a software error[[note]]the thruster-control algorithms used force-pounds, while the high-level software worked in newtons, a problem caused by lack of communication between NASA and its contractors and exacerbated by lack of proper testing[[/note]]).

The United States retains a non-decimal measurement system largely derived from traditional Roman and British units. Technically speaking, the federal government has observed the metric system since it ratified the Metre Convention in 1875, and indeed, the units described below are now legally defined through their metric equivalents rather than their historical origins. The metric system is also almost universally used by the scientific community, though UnitConfusion has sometimes arisen when American and international teams each assumed one was using the other's units. To further complicate matters, the American engineering community has held on to customary units, resulting in occasional disconnects between builders and users of scientific equipment (for example, the loss of the Mars Climate Orbiter, popularly attributed to UnitConfusion, was actually due in large part to this sort of thing, specifically a software error: the thruster-control algorithms used force-pounds, while the high-level software worked in newtons, a problem caused by lack of communication between NASA and its contractors and exacerbated by lack of proper testing). What has come to be known as the "customary system", for lack of a better term, has continued in usage in for a number of factors, including tradition, nationalism, concern over the economic costs of conversion (an attempt by Congress at metrication during TheSeventies was axed for this very reason, as well as lack of political will), and the reasoning that by the time the metric system was introduced in the late eighteenth century, the British units were better-regulated by law than those of its European neighbors, let alone France, whose unwieldy menagerie--around '''250,000''' units, many sharing the same name but varied by locale--was one of the reasons the metric system was created as a sort of ResetButton.

In Canada, Britain, and other Anglophone countries, a cousin of this system also enjoys use (official for some purposes, unofficial for many others) as the "imperial measurements", though their defining values may be slightly different; an ''imperial gallon'', for example, is about 20% more voluminous than its American cousin. There's also some unofficial use in other countries, particularly Latin America, whose proximity to the USA means some prolific use of customary units; for example, where most metricated nations (such as those in Europe) use kilowatts and newtons-meter for power and torque, respectively, Latin American nations still use horsepower and pounds-foot, respectively. Car wheels (and inner dimensions of tires) are almost universally measured in inches. An abortive attempt was made to switch to metric in the early [[TheEighties '80s]]; as of the present, even Michelin, the driving force behind the move, no longer supplies tires to fit these sizes with Michelin-branded ones now made by antique reproduction specialists [[https://www.cokertire.com/ Coker Tire]] in low volume at prices just short of exorbitant. Tire sizes are actually a complicated mix of units, which is fine because almost nobody outside the automotive industry knows, much less cares about, what they mean--the first number is in millimeters, the second a percentage (but may be millimeters), and the last in inches (but may also be millimeters). Fortunately, it's usually trivially obvious if the optional millimeter measurements are used, because the numbers will be much larger (around 2–3× as high for the second number, around ''25×'' as high for the last number).)

The following is intended as a primer for non-Americans to whom the customary units of measurement may seem foreign, cryptic or simply hard to visualize. In modern times, most of these units are defined by their metric equivalents.

On land, 5,280 feet (1,760 yards) make up a '''(statute) mile''' (1.609344 kilometers); originally defined as exactly 5,000 feet, emulating the Roman ''mille passus'', or a thousand paces of five feet each, a 1593 act by the British Parliament shortened the foot in order to accommodate the '''rod''' (5.0282 meters), '''chain''' (four rods, 20.1168 meters), and '''furlong''' (ten chains, 1/8 mile, 201.168 meters), all of which were widely used in surveying at the time (in particular, the latter was originally defined as the distance a team of oxen can plow the land in one run, and is still used in horse racing), allowing the inch, foot, and yard to easily precede these units; while the rod would have an awkward 16.5 feet (5.5 yards) each, the shorter foot is nevertheless tidier than 15.625 pre-1593 feet (or around 5.208333 yards), and there would still be exactly 168 inches to the rod.

The basic unit of liquid volume is the '''gallon''' (3.785411784 liters), defined as 231 cubic inches. Subsequent, smaller divisions are based on powers of two: a gallon is divided into four '''quarts''' (946.352946 milliliters each); a quart into two '''pints''' (473.176473 milliliters each); a pint into two '''cups''' (236.5882365 milliliters each); and a cup into eight '''[fluid] ounces''' (29.5735295625 milliliters each), not to be confused with the ounce discussed above (note, however, that a fluid ounce of a water-based liquid weighs close enough to an ounce avoirdupois for government work; hence the saying "A pint's a pound the world around", which turns a blind eye to every Commonwealth-adjacent part of the world).

For historical reasons, a few dry goods are sold using the dry volume system, whose basic measure is the '''[dry] quart''' (1.101220942715 liters), four of which create a '''[dry] gallon''' (4.40488377086 liters); crops are typically sold by the '''bushel''' (eight gallons, 35.23907016688 liters) or '''peck''' (two gallons, 1/4 bushel, 8.80976754172 liters)--thus Peter Piper picked two dry gallons of pickled peppers. The Commonwealth, on the other hand, standardized the gallon, for both wet and dry goods, as exactly 4.54609 liters, having been originally defined in 1824 as the volume of ten pounds of water at 62°F (17°C); this also results in larger '''imperial pints''' (568.26125 milliliters), so the counterpart to the "pint's a pound..." thing is an imperial gallon weighing ten pounds; the "cup" does not exist as a unit per se, and a Brit seeing "cups" in an American recipe is likely to think "but what ''size'' of cup?".

Prior to the early '70s, American automobile engines listed their displacement in cubic inches (The "409" that Music/TheBeachBoys sung about was a car with a 409-cubic-inch engine). American cars have been built using metric measurements since then, when the energy crisis led to downsizing of engines, and it became preferable to advertisers to describe the size in liters rather than cubic inches. but since some cubic inch-based sizes are closely related to former performance they still pop up now and then. When Music/VanillaIce rapped about his "five-oh," he was referring to the 5.0l Mustang, which was a heavily redesigned "302" that is really closer to 4.9l. Small-block Chevrolet V8s are still closely associated with 350 c.i., although the company hasn't made one (or at least a 5.7l) in years.

America almost exclusively uses the 12-hour clock, which is divided into two intervals -- "AM" (''ante meridiem'', before noon) and "PM" (''post meridiem'', after noon). "8 o'clock" therefore is not a specific enough time in certain circumstances, and would be clarified as "8 o'clock in the morning/evening" (and the "o'clock" is often dropped in casual talk). The 24-hour clock is mostly limited to the military, thus the sobriquet "military time". In the Army and Air Force, 18:00 would be called "eighteen hundred hours", whereas the Navy (and by extension, the Marine Corps) drops "hours" and would simply say "eighteen hundred". Do note that in writing, military time does ''not'' use a colon (e.g., 1800). To a lesser extent, 24-hour time is used by professionals in round-the-clock industries, such as hospitals, transportation, and (increasingly) restaurants.

There is also the ''British Thermal Unit'' (BTU), which is mainly used for things like specifying the amount of heat put out by furnaces. There are various definitions of the BTU, which range between 1,054-1,060 joules. To make things even more confusing to outsiders, American engineers measure cooling in tons (12,000 BTU per hour, equivalent to a ton of ice per day or ~3,516.85 watts) and heating in MBH (a thousand BTU per hour, or ~293.07 watts; the "M" is the Roman numeral for "1,000", not the expected million); both units are also technically measures of ''power'', not energy, but the BTU is an odd enough bird that it's better to keep everything together.

The common unit of power is ''horsepower'', of which there are at least ''seven'' variants, just to be even more confusing. The most common is ''mechanical horsepower'' (AKA ''brake horsepower'', from the method used to derive it), used by auto manufacturers to tell the public that their car is more powerful, and is equivalent to 550 foot-pounds per second (~745.7 watts). There is also ''indicated horsepower'' (an old measurement used for reciprocating steam engines), ''shaft horsepower'', ''metric horsepower'', ''electrical horsepower'', ''boiler horsepower'', and ''hydraulic horsepower'', all of which can be safely ignored, with the sole exception of the metric version, which is sometimes used to rate power outputs of automobiles and other engines in Europe, and always used for Japanese cars. The metric horsepower is sometimes called the ''Pferdestaerke'' (German for "horse strength"), and abbreviated "PS" or (rarely) "cv". The metric horsepower is slightly smaller than its American equivalent, at 735.49875 watts -- for instance, the old Japanese output limit of 280 PS for sports cars is around 276 BHP. You'll also hear references to "SAE net" or "gross" horsepower; specific to car engines, these terms have to do with the testing standard, not the units themselves. SAE gross horsepower, the standard for the auto industry until 1972 and still used in the trucking industry, is measured on a test stand in a pressurized room, with coolant and oil pumped through from outside sources so the engine doesn't have to spin its own pumps. In other words, rigged to give the highest number possible.

Beer is generally sold in 6-packs, with 6 bottles or cans measuring 12 fl. oz. each. Some beers may be sold in loose bottles or cans larger sizes such as 16 oz. (colloquially, a "tallboy"), 19.2 oz. (roughly an Imperial pint), 22 oz. (a "bomber") and 40 oz. (a "forty"). Many bars often have pints available as well as pitchers for larger parties; glass mugs of approximately one liter are also fairly common, particularly in areas settled by people from southern Germany (e.g. the Upper Midwest). A pitcher of beer contains roughly 60 oz, or five bottles' worth. Some bars and restaurants specializing in beer will sell drafts in 20 oz "English" pints. Beer purchased to-go from a bar is typically poured into a "growler", which may be either 32 or 64 ounces. Wine and spirits are typically sold in 750 mL bottles, 750 mL being the round metric number that most closely approximates the pre-metric bottle size of ⅕ gallon (a "fifth"). These bottles, along with the smaller 375 mL and 200 mL bottles, are still colloquially referred to as "fifths", "pints", and "half-pints" despite their volume being slightly less than either. (These terms are more commonly used with spirits; many people just call 750 mL of wine a "bottle", though there are various archaic names for the larger sizes, including "Magnum" for a 1.5L, "Jeroboam" for a 3L, or "Methuselah" for a 6L, all the way up to the 30L "Melchizedek".) Spirits are also sold in 1.75 L bottles, which are colloquially called "handles" after the carrying handle such bottles usually have, or "half-gallons" or "half-g's" because they hold slightly less than half a gallon of spirits. Single-serving size bottles of spirits are 50 mL and are often referred to as "minis" or "airplane bottles" due to their widespread use for mixing drinks on commercial flights.

The alcoholic strength of spirits is described as a percentage of alcohol by volume, and, in the case of spirits, by "degrees proof", where 1 proof = 0.5% ABV. (Contrast British degrees proof, wherein 100 proof equals the point at which gunpowder moistened by the spirit is still capable of ignition, i.e. 57.15% a.b.v, or 114.3 American proof). Several US states regulate alcoholic beverages based on ''alcohol by weight'', which is roughly equivalent to 4/5 of a given product's alcohol by volume; 3.2% ABW beer, the strongest beer that may be sold in grocery stores or convenience stores in several of those states, is roughly 4.0% ABV.

America almost exclusively uses the 12-hour clock, which is divided into two intervals -- "AM" (''ante meridiem'', before noon) and "PM" (''post meridiem'', after noon). "8 o'clock" therefore is not a specific enough time in certain circumstances, and would be clarified as "8 o'clock in the morning/evening." The 24-hour clock is mostly limited to the military, thus the sobriquet "military time". In the Army and Air Force, 18:00 would be called "eighteen hundred hours", whereas the Navy (and by extension, the Marine Corps) drops "hours" and would simply say "eighteen hundred". Do note that in writing, military time does ''not'' use a colon (e.g., 1800). To a lesser extent, 24-hour time is used by professionals in round-the-clock industries, such as hospitals, transportation, and (increasingly) restaurants.

Online Measurement Converter site : https://www.easyunitconverter.com/

Note that since drugs like marijuana[[note]]medical marijuana is legal at the State level in nineteen states, but is still illegal at the Federal level[[/note]], cocaine, LSD, and ecstasy are illegal, they are by definition sold on an unregulated black market. The only guarantee a buyer has for the weight and purity of a particular drug is the good faith of the seller.

Beer is generally sold in 6-packs, with 6 bottles or cans measuring 12 fl. oz. each. Some beers may be sold in loose bottles of larger sizes from 16 oz. (colloquially, a "tallboy") to 40 oz. (a "forty") Many bars often have pints available as well as pitchers for larger parties; glass mugs of approximately one liter are also fairly common, particularly in areas settled by people from southern Germany (e.g. the Upper Midwest). A pitcher of beer contains roughly 60 oz, or five bottles' worth. Some bars and restaurants specializing in beer will sell drafts in 20 oz "English" pints. Beer purchased to-go from a bar is typically poured into a "growler", which may be either 32 or 64 ounces. Wine and spirits are typically sold in 750 mL bottles, 750 mL being the round metric number that most closely approximates the pre-metric bottle size of ⅕ gallon (a "fifth"). These bottles, along with the smaller 375 mL and 200 mL bottles, are still colloquially referred to as "fifths", "pints", and "half-pints" despite their volume being slightly less than either. (These terms are more commonly used with spirits; many people just call 750 mL of wine a "bottle", though there are various archaic names for the larger sizes, including "Magnum" for a 1.5L, "Jeroboam" for a 3L, or "Methuselah" for a 6L, all the way up to the 30L "Melchizedek".) Spirits are also sold in 1.75 L bottles, which are colloquially called "handles" after the carrying handle such bottles usually have, or "half-gallons" or "half-g's" because they hold slightly less than half a gallon of spirits. Single-serving size bottles of spirits are 50 mL and are often referred to as "minis" or "airplane bottles" due to their widespread use for mixing drinks on commercial flights.

The basic unit of length is the '''foot''' (30.48 centimeters), which is divided into twelve '''inches''' (2.54 centimeters each). When greater precision is required, fractions of an inch are used (generally based on powers of 2, such as ½, ¼, ⅛, and so on), except in certain engineering disciplines which use decimal derivations. Feet and inches are commonly abbreviated by apostrophes (one for feet, two for inches -- e.g., 6 feet and 4 inches [193 cm] becomes 6'4"). Three feet make up a '''yard''' (91.44 centimeters), which is more commonly encountered in UsefulNotes/AmericanFootball, as well as the basis of the current measurement system, defined in a 1959 agreement with Britain, Canada, Australia, New Zealand and South Africa as exactly 0.9144 meter.

On land, 5,280 feet (1,760 yards) make up a '''(statute) mile''' (1.609344 kilometers); originally defined as exactly 5,000 feet, emulating the Roman ''mille passus'', or a thousand paces of five feet each, a 1593 act by the British Parliament shortened the foot in order to accommodate the '''rod''' (5.0282 meters), '''chain''' (4 rods, 20.1168 meters), and '''furlong''' (10 chains, ⅛ mile, 201.168 meters), all of which were widely used in surveying at the time (in particular, the latter was originally defined as the distance a team of oxen can plow the land in one run and is still used in horse racing), allowing the inch, foot and yard to easily precede these units; while the rod would have an awkward 16.5 feet (5.5 yards) each, the shorter foot is nevertheless tidier than 15.625 pre-1593 feet (or around 5.208333 yards), and there would be exactly 168 inches to the rod.

In navigation, the '''nautical mile''' is used; unlike its land-based cousin, however, this mile is longer and unwieldy at around 6,076.1155 feet (1.1508 miles), or exactly 1,852 meters; as it was historically defined as one-sixtieth of an arc-degree of Earth's latitude (thus one arc-minute) and currently defined in metric terms, it is one of the few non-metric units officially tolerated for use among nations where the metric system is enforced. Water depth is also measured in '''fathoms''' (6 feet, 1.8288 meters).

Two smaller units, the '''point''' (1/72 inch, around 0.3528 millimeters) and '''pica''' (12 points, 1/6 inch, around 4.2333 millimeters), are used in graphic design and typesetting. Outside those fields, one is liable to run into points in the context of [[UsefulNotes/{{Fonts}} font]] sizes (though usage for font sizes on a computer screen is mostly traditional and will not usually reflect the actual physical size of a font -- technically, a 12-point font should render in the same physical size regardless of the physical size of the screen and screen resolution).

The basic unit of mass is the '''(avoirdupois) pound''' (453.59237 grams), which is divided into sixteen '''ounces''' (28.349523125 grams each)[[note]]Some will insist that the pound is actually a base unit of force (~4.448 newtons), and that the basic unit of mass is the ''slug'', one "pound-force" (lbf) over a foot per second squared (14.59 kilograms.) The "pound-mass" (lbm) described here would then be defined as one pound-force over "standard gravity" (an estimate of gravity at sea level equal to 9.80665 meters per second per second) so that one pound-mass will weigh one pound-force, a very simple equivalency. When dealing with sources of acceration other than gravity, however, using pound-force and pound-mass would require dividing standard gravity back out of the equation; using slugs simplifies the calculations. [[/note]]. The pound can be further divided into 7,000 '''grains''' (64.79891 milligrams each), though it is seldom used except in certain specialized fields, mostly archery and firearms.

2,000 pounds make a '''(short) ton''' (907.18474 kilograms), while the heavier '''(imperial) ton''', used in Britain, weighs 2,240 pounds (1,016.0469088 kilograms); the discrepancy has to do with a pair of units more-or-less unique to the British system, the '''stone''' (14 pounds, 6.35029318 kilograms), the '''hundredweight''' (112 pounds, 1/20 ton, 50.80234544 kilograms; the even more uncommon American version has been trimmed to exactly 100 pounds).

Those who deal with precious metals use the '''troy pound''' (144⁄175 avoirdupois pound or 373.2417216 grams), defined as 5,760 grains. The troy pound consists of twelve '''troy ounces''' (31.1034768 grams each), in contrast to sixteen for its avoirdupois version. When one refers to both units, the standard ounce and pound are sometimes called ''ounce avoirdupois'' and ''pound avoirdupois'', respectively, to avoid confusion.

The basic unit of liquid volume is the '''gallon''' (3.785411784 liters), defined as 231 cubic inches. A gallon is divided into four '''quarts''' (946.352946 milliliters each), which is divided into two '''pints''' (473.176473 milliliters each), divided in turn into two '''cups''' (236.5882365 milliliters each), each divided ''again'' into eight '''fluid ounces''' (29.5735295625 milliliters each), not to be confused with the ounce discussed above (note, however, that a fluid ounce of a water-based liquid weighs close enough to an ounce avoirdupois for government work; hence the saying "A pint's a pound the world around", which turns a blind eye to every [ex-]British part of the world).

For historical reasons, a few dry goods are sold using the dry volume system, whose basic measure is the '''(dry) quart''' (1.101220942715 liters), four of which create a '''(dry) gallon''' (4.40488377086 liters); crops are typically sold by the '''bushel''' (8 dry gallons or 35.23907016688 liters) or '''peck''' (2 dry gallons, ¼ bushel or 8.80976754172) -- thus Peter Piper picked two dry gallons of pickled peppers. The Commonwealth, on the other hand, standardized the gallon, for both wet and dry goods, as exactly 4.54609 liters, having been originally defined in 1824 as the volume of ten pounds of water at 62°F (17°C); this also results in larger '''imperial pints''' (568.26125 milliliters each), so the counterpart to the "pint's a pound..." thing is an imperial gallon weighing ten pounds; the "cup" does not exist as a unit per se, and a Brit seeing "cups" in an American recipe is likely to think "but what ''size'' of cup?".

42 liquid gallons equal a '''petroleum barrel''' (158.987294928 liters), the standard international unit in which oil is sold, but most other liquids sold by the barrel use a definition of 31.5 gallons. A barrel of whiskey, however, is larger than a petroleum or "standard" barrel, at 53 gallons (200.62682455 liters). The '''buttload''' (476.961884784 liters) is now used just to mean "a lot", but it used to be two '''hogsheads''' of 63 gallons each (238.480942392 liters), used to measure wine.

Cooks use three additional units: the '''teaspoon''' (~4.9289 milliliters), '''tablespoon''' (3 tablespoons, ½ fluid ounce or 14.78675 milliliters), and '''kitchen cup''' (16 tablespoons, 8 fluid ounces, or 236.588 milliliters), which is slightly more voluminous than the fluid cup above. Two cups make a '''pint''' (473.176 milliliters).

Ingredients in recipes are usually measured by volume, not weight (save meat and produce, which are bought by the pound). Most households do not possess a kitchen scale, thus these are generally priced only for the upscale or gourmet market, and can cost significantly more than an accurate measuring cup (e.g. 50¢ for a cup vs. $30+ for the cheapest scale at large chain houseware stores). Americans therefore tend to see British recipes as inaccessible and "only for snooty gourmets."

In Canada, Britain, and other Anglophone countries, a cousin of this system also enjoys non-official use as the "imperial measurements", though their defining values may be slightly different; an ''imperial gallon'', for example, is about 20% more voluminous than its American cousin. There's also some unofficial use in other countries, particularly Latin America, whose proximity to the USA means some prolific use of customary units; for example, where most metricated nations (such as those in Europe) use kilowatts and newtons-meter for power and torque, respectively, Latin American nations still use horsepower and pounds-foot, respectively. Car wheels (and inner dimensions of tires) are almost universally measured in inches. An abortive attempt was made to switch to metric in the early [[TheEighties '80s]]; as of the present, even Michelin, the driving force behind the move, no longer supplies tires to fit these sizes with Michelin-branded ones now made by antique reproduction specialists [[https://www.cokertire.com/ Coker Tire]] in low volume at prices just short of exorbitant. Tire sizes are actually a complicated mix of units, which is fine because almost nobody outside the automotive industry knows, much less cares about, what they mean--the first number is in millimeters, the second a percentage (but may be millimeters), and the last in inches (but may also be millimeters). Fortunately, it's usually trivially obvious if the optional millimeter measurements are used, because the numbers will be much larger (around 2–3× as high for the second number, around ''25×'' as high for the last number).)

Incidentally, many folks like to say that the United States uses the Imperial Measurement System, [[YouKeepUsingThatWord which is not the same as American Customary Units]]. The Imperial units were standardized in 1824, [[UsefulNotes/TheAmericanRevolution well after the USA stopped paying much heed to Westminster's declarations]], while the United States customary units were based on older British units and standardized in the 1890s (the measurements now being defined by their metric equivalents, as mentioned above). Both systems are close enough to the same for most day-to-day usage that most Americans don't know or care about the difference anyways.

->''"36-24-36? Only if she's 5'3"!"''
-->-- Music/SirMixALot, "Baby Got Back"

->''See the Useful Notes article on UsefulNotes/AmericanMoney.

The basic unit of mass is the '''(avoirdupois) pound''' (453.59237 grams), which is divided into sixteen '''ounces''' (28.349523125 grams each)[[note]]Some will insist that the pound is actually a base unit of force (~4.448 newtons), equal to the measurement above multiplied by "standard gravity" (exactly 9.80665 meters per second per second), a uselessly overprecise estimate of gravity at sea level, and that the basic unit of mass is the ''slug'', one pound-force over a foot per second squared (14.59 kilograms.[[/note]]. The pound can be further divided into 7,000 '''grains''' (64.79891 milligrams each), though it is seldom used except in certain specialized fields, mostly archery and firearms.

In Canada, Britain and other Anglophone countries, a cousin of this system also enjoys non-official use as the "imperial measurements", though their defining values may be slightly different; an ''imperial gallon'', for example, is about 20% more voluminous than its American cousin. There's also some unofficial use in other countries, particularly Latin America, whose proximity to the USA means some prolific use of customary units; for example, where most metricated nations (such as those in Europe) use kilowatts and newtons-meter for power and torque, respectively, Latin American nations still use horsepower and pounds-foot, respectively. Car wheels (and inner dimensions of tires) are almost universally measured in inches. An abortive attempt was made to switch to metric in the early [[TheEighties '80s]]; as of the present, even Michelin, the driving force behind the move, no longer supplies tires to fit these sizes with Michelin-branded ones now made by antique reproduction specialists [[https://www.cokertire.com/ Coker Tire]] in low volume at prices just short of exorbitant. Tire sizes are actually a complicated mix of units, which is fine because almost nobody outside the automotive industry knows, much less cares about, what they mean--the first number is in millimeters, the second a percentage (but may be millimeters), and the last in inches (but may also be millimeters). Fortunately, it's usually trivially obvious if the optional millimeter measurements are used, because the numbers will be much larger (around 2–3× as high for the second number, around ''25×'' as high for the last number).)

The United States retains a non-decimal measurement system largely derived from traditional British units. Technically speaking, the federal government has observed the metric system since it ratified the Metre Convention in 1875, and indeed, the units described below are now legally defined through their metric equivalents rather than their historical origins. The metric system is also almost universally used by the scientific community, though UnitConfusion has sometimes arisen when American and international teams each assumed one was using the other's units. To further complicate matters, the American engineering community has held on to customary units, resulting in occasional disconnects between builders and users of scientific equipment (for example, the loss of the Mars Climate Orbiter, popularly attributed to UnitConfusion, was actually due in large part to this sort of thing, specifically a software error: the thruster-control algorithms used force-pounds, while the high-level software worked in newtons, a problem caused by lack of communication between NASA and its contractors and exacerbated by lack of proper testing). What has come to be known as the "customary system", for lack of a better term, has continued in usage in for a number of factors, including tradition, nationalism, concern over the economic costs of conversion (an attempt by Congress at metrication during TheSeventies was axed for this very reason, as well as lack of political will), and the reasoning that by the time the metric system was introduced in the late eighteenth century, the British units were better-regulated by law than those of its European neighbors, let alone France, whose unwieldy menagerie--around '''250,000''' units, many sharing the same name but varied by locale--was one of the reasons the metric system was created as a sort of ResetButton.

->''"The metric system is the tool of the devil! My car gets forty rods to the hogshead[[note]]About 0.002 MPG... about ten and a half feet. That's very, very, bad.[[/note]], and that's the way I likes it!"''\\

->''"36-24-36? Only if she's 5'3"!"''\\

The basic unit of liquid volume is the '''gallon''' (3.785411784 liters), defined as 231 cubic inches. A gallon is divided into four '''quarts''' (946.352946 milliliters each), which is divided into two '''pints''' (473.176473 milliliters each), divided in turn into two '''cups''' (236.5882365 milliliters each), each divided ''again'' into eight '''fluid ounces''' (29.5735295625 milliliters each), not to be confused with the ounce discussed above (note, however, that a fluid ounce of a water-based liquid weighs close enough to an ounce avoirdupois for government work; hence the saying "A pint's a pound the world around," which turns a blind eye to every [ex-]British part of the world).

42 liquid gallons equal a '''petroleum barrel''' (158.987294928 liters), the standard international unit in which oil is sold, but other liquids sold in barrels typically that which measures 31.5 gallons each. The '''buttload''' (476.961884784 liters) is now used just to mean "a lot", but it used to be two '''hogsheads''' of 63 gallons each (238.480942392 liters), used to measure wine.

The United States retains a non-decimal measurement system largely derived from traditional British units. Technically speaking, the federal government has observed the metric system since it ratified the Metre Convention in 1875, and indeed, the units described below are now legally defined through their metric equivalents rather than their historical origins. The metric system is also almost universally used by the scientific community, though UnitConfusion has sometimes arisen when American and international teams each assumed one was using the other's units. To further complicate matters, the American engineering community has held on to customary units, resulting in occasional disconnects between builders and users of scientific equipment (for example, the loss of the Mars Climate Orbiter, popularly attributed to UnitConfusion, was actually due in large part to this sort of thing, specifically a software error: the thruster-control algorithms used force-pounds, while the high-level software worked in newtons, a problem caused by lack of communication between NASA and its contractors and exacerbated by lack of proper testing). What has come to be known as the "customary system", for lack of a better term, has continued in usage in for a number of factors, including tradition, national pride, concern over the economic costs of conversion (an attempt by Congress at metrication during TheSeventies was axed for this very reason, as well as lack of political will), and the fact that by the time the metric system was introduced in the late eighteenth century, Americans already inherited a system better-regulated by law than those of its European neighbors, let alone France, whose unwieldy menagerie--around '''250,000''' units, many sharing the same name but varied by locale--was one of the reasons the metric system was created as a sort of ResetButton.

Incidentally, many folks like to say that the United States uses the Imperial Measurement System, [[YouKeepUsingThatWord which is not the same as American Customary Units]]. The Imperial units were standardized in 1824, [[UsefulNotes/TheAmericanRevolution well after the US stopped paying much heed to the British government's declarations]], while the United States customary units were based on the older British Units and standardized in the 1890s (the measurements now being defined by their Metric equivalents, as mentioned above). Both systems are close enough to the same for most day-to-day usage that most Americans don't know or care about the difference anyways.

The basic unit of length is the '''foot''' (30.48 centimeters), which is divided into twelve '''inches''' (2.54 centimeters each). When greater precision is required, fractions of an inch are used (generally based on powers of 2, such as ½, ¼, ⅛, and so on), except in certain engineering disciplines which use decimal derivations. Feet and inches are commonly abbreviated by apostrophes (one for feet, two for inches -- e.g., 6 feet and 4 inches [193 cm] becomes 6'4"). Three feet make up a '''yard''' (91.44 centimeters), which is more commonly encountered in American football, as well as the basis of the current measurement system, defined in a 1959 agreement with Britain, Canada, Australia, New Zealand and South Africa as exactly 0.9144 meter.

On land, 5,280 feet (1,760 yards) make up a '''(statute) mile''' (1.609344 kilometers); originally defined as exactly 5,000 feet, emulating the Roman ''mille passus'', or a thousand paces of five feet each, a 1593 act by the British Parliament shortened the foot in order to accommodate the '''furlong''' (1/8 mile or 201.168 meters), '''chain''' (1/10 furlong or 20.1168 meters) and '''rod''' (1/4 chain or 5.0292 meters), all of which were widely used in surveying at the time (with the furlong originally defined as the distance a team of oxen can plow the land in one run and is still used in horse racing), allowing the inch, foot and yard to easily precede these units; while the rod would have an awkward 16.5 feet (5.5 yards) each, the shorter foot is nevertheless tidier than 15.625 pre-1593 feet (or around 5.208333 yards), and there would be exactly 168 inches to the rod.

In navigation, the '''nautical mile''' is used; unlike its land-based cousin, however, this mile is longer and unwieldy at around 6,076.1155 feet (1.1508 miles), or exactly 1,852 meters; as it was historically defined as one-sixtieth of an arc-degree of Earth's latitude (thus one arc-minute) and currently defined in metric terms, it is one of the few non-metric units officially tolerated for use by metric-using countries. Water depth is also measured in '''fathoms''' (six feet or 1.8288 meters).

Since 1959, the foot has been standardized to exactly 30.48cm. For historical compatibility, though, real estate maps are still drawn in the older '''survey foot''' (1200/3937 meters or around 30.48006 centimeters).

Two smaller units, the '''point''' (1/72 inch or around 0.3528 millimeters) and '''pica''' (12 points, 1/6 inch or around 4.2333 millimeters), are used in graphic design and typesetting. Outside those fields, one is liable to run into points in the context of [[UsefulNotes/{{Fonts}} font]] sizes (though usage for font sizes on a computer screen is mostly traditional and will not usually reflect the actual physical size of a font -- technically, a 12-point font should render in the same physical size regardless of the physical size of the screen and screen resolution).

In area, an '''acre''' (4,046.8564224 square meters, or just over 40% of a hectare) is defined as the area of a rectangle measuring one chain by one furlong (66×660 feet), or 43,560 square feet (4,840 square yards). Outside agriculture, the '''square mile''' (640 acres or 258.9988110336 hectares) is used.

2,000 pounds make a '''(short) ton''' (907.18474 kilograms), while the longer '''imperial ton''', used in Britain, weighs 2,240 pounds (1,016.0469088 kilograms); the inequality has to do with the '''stone''' (fourteen pounds or 6.35029318 kilograms), a unit almost unheard of in America but remains in British conversation, eight of which form a '''hundredweight''' (112 pounds or 50.80234544 kilograms), twenty of which form the imperial ton.

*** Not to be confused with the metric "m" for "meter". [[note]]"meters per hour" is usually written as m/h... but "kilometers per hour" is usually kph.[[/note]]

The United States retains a non-decimal measurement system largely derived from traditional British units. Technically speaking, the federal government has observed the metric system since it ratified the Metre Convention in 1875, and indeed, the units described below are now legally defined through their metric equivalents rather than their historical origins. The metric system is also almost universally used by the scientific community, though UnitConfusion has sometimes arisen when American and international teams each assumed one was using the other's units. To further complicate matters, the American engineering community has held on to customary units, resulting in occasional disconnects between builders and users of scientific equipment (for example, the loss of the Mars Climate Orbiter, popularly attributed to UnitConfusion, was actually due in large part to this sort of thing, specifically a software error: the thruster-control algorithms used force-pounds, while the high-level software worked in newtons, a problem caused by lack of communication between NASA and its contractors and exacerbated by lack of proper testing). What has come to be known as the "customary system", for lack of a better term, has continued in usage in for a number of factors, including tradition, national pride, concern over the economic costs of conversion (an attempt by Congress at metrication during TheSeventies was axed for this very reason, as well as lack of political will), and the fact that by the time the metric system was introduced in the late seventeenth century, Americans already inherited a system better-regulated by law than those of its European neighbors, let alone France, whose unwieldy menagerie--around '''250,000''' units, many sharing the same name but varied by locale--was one of the reasons the metric system was created as a sort of ResetButton.

America almost exclusively uses the 12-hour clock, which is divided into two intervals -- "AM" (''ante meridiem'', before noon) and "PM" (''post meridiem'', after noon). "8 o'clock" therefore is not a specific enough time in certain circumstances, and would be clarified as "8 o'clock in the morning/evening." The 24-hour clock is mostly limited to the military, thus the sobriquet "military time". In the Army and Air Force, 18:00 would be called "eighteen hundred hours", whereas the Navy (and by extension, the Marine Corps) drops "hours" and would simply say "eighteen hundred". To a lesser extent, 24-hour time is used by professionals in round-the-clock industries, such as hospitals, transportation, and (increasingly) restaurants.

Marijuana is usually purchased in weights measuring ⅛th of an ounce, or it is measured in grams for smaller quantities. The same goes for "magic" psilocybin mushrooms. Cocaine is sold by the gram or 8-ball, which is 3.5 grams (just under ⅛ of an ounce hence the name). LSD can come in liquid form, measured in micrograms, or is sold on cardboard strips known as "blotters." Drugs like Ecstasy typically come in quarter-gram pills, which are sold individually (though the weight of active MDMA in the pill will be substantially lower than that). There's an old joke that "drugs are God's way of teaching Americans the metric system."

Note that since drugs like Marijuana[[note]]medical marijuana is legal at the State level in nineteen states, but is still illegal at the Federal level[[/note]], Cocaine, LSD, and Ecstacy are illegal, they are by definition sold on an unregulated black market. The only guarantee a buyer has for the weight and purity of a particular drug is the good faith of the seller.