American Customary Measurements: Difference between revisions
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36-24-36. (Maybe, if she's 5'3".)
Whereas in most of the world [[The Metric System Is Here to Stay|the metric system has come into near-universal use]] by ordinary citizens, the US retains a non-decimal system of measurement largely derived from traditional English units. Technically speaking, the US government has observed the metric system since it ratified the Convention on the Meter in the late 19th century, and indeed, the customary units described below are now legally defined in terms of their metric equivalents rather than their historical origins. The metric system is also almost universally used by the scientific community, though [[Unit Confusion]] 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 the builders and users of scientific equipment (for example, loss of the Mars Climate Orbiter, popularly attributed to unit confusion between American and European space agencies, was actually due in large part to this sort of thing <ref>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.</ref> ). What has come to be known as the "customary system", for lack of a better term, has continued in usage in the US for a number of factors, including tradition, national pride, and the expense of conversion. An attempt by Congress to mandate metric conversion in the 1970s failed primarily because of the last reason (and the lack of political will to ''insist''). Only the bottling industry switched, but not for that reason. One company (Dr Pepper) advertised the small size gain from 2 quarts to 2 liters, and all other companies followed, which is why 2 liter bottles (and more recently, 1 liter bottles) are in metric but smaller units are in Fluid Oz.
In Canada, Britain and other English-speaking countries, these units also enjoy non-official use (known as Imperial measurements, after the British Empire), though their defining values may be slightly different; an Imperial gallon, for example, is about 1.2 American gallons. This is, combined with mixing randomly with metric units, of course part of the secret British plan to confuse ''all'' foreign visitors. There's also some unofficial use in other countries, particularly in Latin America, where the close proximity to the USA means Imperial units are sometimes used instead of Metric units; engine power and torque, for example, is often measured in Europe in kilowatts and newtons-meter (kW and Nm), while in Latin America the former is sometimes measured in horsepower and the latter in pounds-foot. Car wheels (and tire inner dimensions) are almost universally measured in inches, worldwide. An abortive attempt was made to switch to metric in the early [[The Eighties|80s]]; at this writing (2008) only Michelin supplies tires to fit these sizes, in low volume at prices just short of exorbitant.
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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.
'''Distance'''. The basic unit of distance is the foot (0.3048 m), which is divided into twelve inches (2.54
Since 1959, the foot has been internationally defined as exactly 30.48
Two smaller units, "points" and "picas", are used in graphic design and typesetting, and refer to one twelfth and one seventy-second of an inch. Outside those fields, one is liable to run into "points" in the context of [[Useful Notes/Fonts|font]] sizes (though the usage of point measurements for font sizes on a computer screen is mostly traditional and will not usually reflect the actual physical size of a
One notable exception to all of this is the US automotive industry. They standardized on metric fasteners in [[The Eighties]], and because of this, it's common to see both fractional-inch and metric sized sockets and wrenches in toolkits. Also, in some circles, lengths of less than a half-inch or so are given in millimeters because they're easier to work with; things like the tips on writing instruments and the width of photo film have been measured in mm for decades.
'''Mass.''' The basic unit of mass is the pound, defined as 453.59237 grams, which is further divided into 16 ounces (~28.35 g).
'''Volume.''' The basic unit of liquid volume is the gallon, defined as 231 cubic inches (~3.79 L). This is divided into four quarts (around 946.35 mL), each of which are divided into two pints (~473.18 mL), divided in turn into two cups (~236.59 mL), each divided into eight fluid ounces (~29.57 mL), not to be confused with the avoirdupois ounce or troy ounce discussed above. (Note, however, that a fluid ounce of a water-based liquid weighs close enough to one ounce avoirdupois for government work; hence the American saying "A pint's a pound the world around," which turns a blind eye to every British part of the world.) For historical reasons, a few dry goods (such as strawberries and cherry tomatoes) are sold using the dry volume system, where one quart is 1.101220942715 L (again, exactly); crops are typically sold by the bushel, which is 8 dry gallons, or peck, which is 2 -- so Peter Piper picked 2 dry gallons of pickled peppers. The Commonwealth, on the other hand, defines a gallon, both wet and dry, as exactly 4.54609 L, with all other units adjusted accordingly. Forty-two US gallons equal a petroleum barrel (~158.99 L), the standard international unit in which oil is sold, but other liquids sold in "barrels" typically use a 31.5 gallon barrel.
Spaces you don't expect to fill with liquid (car trunks, apartments, warehouses, etc.) are expressed in cubic
Cooks use three additional units: the teaspoon (5 mL), the tablespoon (15 mL), and the kitchen cup (240 mL), slightly more (or less in the Commonwealth) than the fluid cup above. Three teaspoons make a tablespoon, two tablespoons make about a fluid ounce, sixteen tablespoons make a cup, and two cups make a pint.
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'''Dates and Time''': America almost exclusively uses the 12 hour clock, which is divided into two intervals "A.M." (''ante meridiem'', before noon) and "P.M." (''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" or "in the evening." The 24 hour clock has limited use in America, being used primarily in the military (thus the sobriquet "military time"). In the Army and Air Force, 18:00 would be called "eighteen hundred hours", whereas the Navy drops the "hours" and would simply say "eighteen hundred". To a lesser extent, 24-hour time is used in America by professionals in industries that operate around the clock, such as hospitals, transportation, and (increasingly) restaurants.
As to dates, they are written in the month/day/year format instead of the European day/month/year. December
'''Money''': The standard unit of American money is called the ''dollar'', presumably from the German word "Taler"<ref>possibly indirectly through the Spanish eight-real coin, called the Spanish Dollar (and occasionally the ''Dollero'') because of its resemblance to the ''taler'' coin. The Spanish Dollars were more popular in early America for their finer silver.</ref> which was used for various now obsolete currencies and is originally derived from "Joachimsthal", a town in Bohemia where coins were minted. It is subdivided into 100 individual units, ''cents''. Each cent is in turn further divided into 10 ''mills'', a unit of currency largely rendered hypothetical through inflation (except in the price of gasoline, although property-tax rates are often expressed in mills), of which there are 1000 in a dollar. Each cent is one one hundredth of a dollar, and comes in the form of a small coin made of <s>copper</s> <s>wax</s> <s>bronze</s> <s>steel</s> zinc with a copper coating.
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The second is the kilowatt-hour (3.6 MJ), mostly used by electric companies. Most Americans know what a watt is through electrical device ratings, so to make things more intuitive, power meters in the US use this composite unit (the amount of energy used by a 1000-watt appliance in 1 hour) instead of measuring things directly in joules.
The third customary unit of energy in the United States is the calorie (~4.184 J), used in heating, nutrition, and kinesiology. An odd duck of sorts, the calorie, based on the specific heat of water, was introduced as a metric unit in 1824, but was displaced within the System Internationale by the joule - but not before it found usage within the United States. The unit most Americans refer to when they say "calorie"
There is also the "British Thermal Unit", normally abbreviated 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 from about 1,054 to 1,060 J according to the other wiki. To make things even more confusing to outsiders, American Engineers measure cooling in tons (12,000 BTU/hr, equivalent to 1 ton of ice per day or ~3516.85 W) and heating in MBH (one thousand BTU/hr or ~293.07 W; the M is the Roman numeral for 1000, not the expected one million); both of those 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.
'''Power:''' The common unit of power in the United States is the horsepower. There are five different types of horsepower, just to be even more confusing. The most common is Mechanical horsepower (more often called brake horsepower, from the method used to derive it) which is used by auto manufacturers to tell [[Viewers are Morons|the public]] that their car is more powerful and therefore makes you more of a man if you own it. 1 unit of mechanical horsepower is 550 foot-pounds per second (~745.7 W). There is also metric horsepower, electrical horsepower, boiler horsepower, and hydraulic horsepower, all of which can be safely ignored, with the sole exception of metric horsepower, which is sometimes used to rate power outputs of automobiles and other engines in Europe and always used for cars in Japan. 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 W --for instance, the old Japanese output limit of 280 PS for sports cars is around 276
All that said, you're unlikely to see horsepower used outside of the automotive (and the propeller aviation and helicopter aviation) realm or certain kinds of electrical motors. As noted above, all electrical appliances in the US specify their rated consumption in watts (or the equivalent in volts and amperes), especially light bulbs and pretty much anything with a heating element in it. Ads for things electronic also tend to boast about how many watts they can output, especially high-power audio amplifiers and, sometimes, even the radio stations themselves.
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Marijuana is usually purchased in weights measuring 1/8th 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 1/8 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,<ref>medical marijuana is legal at the State level in California, but is still illegal at the Federal level</ref>
'''Abbreviations:''' The words are usually not spelled out, so here are the relevant abbreviations (and symbols):
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* mi: Miles
** Except for mph (miles per hour)
*** Not to be confused with the metric "m" for "meter".
* oz: Ounces
* yd: Yards
For those wondering, a hogshead is 63 U.S. liquid gallons, and a rod is 16.5 feet. 40 rods to a hogshead, as mentioned in the quote above, works out to approximately 120,000 liters per 100
In miles per gallon that's statistical zero.<ref>
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