Some would argue that the decline of manufacturing industry in the USA contributed to Mr Trump’s surprising victory in the Presidential election*. Others might say that manufacturing’s decline was due in part to the tardy adoption of the international system of measures. Here we look at some of the quirks of ‘English measures’, a throw back to the USA’s colonial past and still widely used in America today.
Many champions of the imperial system often point to survival of ‘English’ units in the United States to justify their contiued use in Britain. However, while US Customary aka ‘English’ units have many features in common with the imperial system, there are some differences. In particular, Americans uses some units that are virtually unknown in the UK and which many Britons would find curious and surprising. Here, Ronnie Cohen looks at some of the quirks of these units. All the information here can be found in Appendix C of the US National Institute of Standards and Technology (NIST) document, “General Tables of Units of Measurement”.
The Americans have two versions of the inch, foot, yard, statute mile and all the other related imperial units of length used on land. They have survey and international measures. Survey measures are only used for land survey data. Both are defined in terms of metric units. The survey foot is exactly 1200/3937 metres and the international foot is exactly 0.0254 x 39.37 survey foot. The survey mile and international mile differ by just 3 millimetres. This is equivalent to less than 2 parts of million. The difference between survey and international measures also affects area measurements, e.g.
- One square survey foot = 1.000 004 square international feet
- One square survey mile = 1.000 004 square international miles
As well as the use of survey measures, the NIST also provides definitions of some large land measures not seen in the UK. In the US, 1 section of land equals 1 square mile and 1 township equals 6 square miles. Hence 1 township = 36 sections = 36 square miles.
Here is some factual information provided by NIST about the origin of the statute mile and the international nautical mile that few people know:
“The term ‘statute mile’ originated with Queen Elizabeth I who changed the definition of the mile from the Roman mile of 5000 feet to the statute mile of 5280 feet. The international mile and the US statute mile differ by about 3 millimetres although both are defined as being equal to 5280 feet. The international mile is based on the international foot (0.3048 metres) whereas the U.S. statute mile is based on the survey foot (1200/3937 metres).
The international nautical mile of 1852 metres (6076.115 49 feet) was adopted effective July 1, 1954, for use in the United States. The value formerly used in the United States was 6080.20 feet = 1 nautical (geographical or sea) mile.”
The US has different volume measures for solids and liquids. Units for dry measures are approximately one-sixth larger than their equivalent liquid units. For example, one liquid pint equals 28.875 cubic inches whereas one dry pint equals 33.6003 cubic inches.
For liquid measures there are 16 fuid ounces in a pint, compared with 20 in the imperial system. The US fluid ounce, pint, quart and gallon differ from the imperial units of the same name. However, the yard, the avoirdupois pound, the troy pound, and the apothecaries pound are identical with the imperial units.
Another source of confusion over volume measures is the difference between standard liquid measures and apothecaries liquid measures. Standard and apothecaries liquid volumes are both based on the liquid gallon of 231 cubic inches. However, the breakdown of units for standard and apothecaries liquid volumes is different. Neither is compatible with the other.
The USA officially recognises two different hundredweights and tons. These are the short and long (a.k.a. gross) hundredweight and ton. Believe it or not, the USA uses both although the short measures are used for most purposes. NIST says that the gross or long ton and hundredweight are used commercially in the United States to only a very limited extent, usually in restricted industrial fields and that the units are the same as the British “ton” and “hundredweight”.
Other curiosities in the US customary system mentioned in the NIST document include:
- 1 cable’s length = 120 fathoms (exactly) = 720 feet (exactly)
- 1 hand = 4 inches
- 1 league (land) = 3 U.S. statute miles (exactly)
- 1 point (typography) = 0.013 837 inch (exactly)
- 1 square (building) = 100 square feet
- 1 cord (firewood) = 128 cubic feet (exactly)
- 1 water ton (English) = 270.91 U.S. gallons = 224 British Imperial gallons (exactly)
- 1 assay ton = 29.167 grams
- 1 micro pound = 0.000 001 pound (lb)
- 1 mil = 0.001 inch (exactly)
It is clear that the micropound and mil clearly borrow the decimal features from the metric system. The Gunter’s or surveyors chain foreshadowed the metric system (e.g. 1 furlong = 10 chains = 1000 links). These features of non-metric units show that their users clearly see the benefits of using a decimal-based measurement system. However, the metric system is almost entirely based on powers of 10 (i.e. all decimal-based). We could ask, if Americans want to benefit from decimal-based measurements, why don’t they just use the metric system?
NIST says that the assay ton is used in assaying and that the assay ton bears the same relation to the milligram that a ton of 2000 pounds avoirdupois bears to the ounce troy; hence the mass in milligrams of precious metal obtained from one assay ton of ore gives directly the number of troy ounces to the net ton.
The Americans use a variety of different barrels that vary in size betwee 31 and 42 gallons. In this context, the term “gallon” refers to the US liquid gallon. Cranberries have a barrel all to themselves while all other fruits, vegetables, and other dry commodities use a different barrel. A variety of other barrels are established by law or usage.
- 1 standard barrel for fruits, vegetables, and other dry commodities, except cranberries = 7056 cubic inches = 105 dry quarts = 3.281 bushels, struck measure
- 1 standard barrel just for cranberries = 5826 cubic inches = 86 + 45/64 dry quarts = 2.709 bushels, struck measure
- 1 federal liquid barrel = 31 gallons (the basis for federal taxes on fermented liquors)
- a widely used state liquid barrel = 31½ gallons
- a cistern measurement barrel in one state = 36 gallons
- 1 federal proof spirits barrel = 40 gallons
- 1 oil barrel = 42 gallons (this barrel is recognized for liquids by 4 states)
There are different bushels for heaped and struck measure:
- 1 bushel (U.S.) struck measure = 2150.42 cubic inches (exactly)
- 1 bushel, heaped (U.S.) = 2747.715 cubic inches = 1.278 bushels, struck measure
- 1 bushel (British Imperial) (struck measure) = 1.032 US bushels, struck measure = 2219.36 cubic inches
The heaped US bushel is frequently recognised as 1¼ bushels, struck measure.
Cups, teaspoons and tablespoons remain in common use for recipes in the US and I do not mean kitchen utensils but standard US measurements. Now that recipes in the UK are overwhelmingly metric, I suspect that most Britons would have no idea what quantities cups, teaspoons and tablespoons represent if they saw them in a recipe. These measurements are rarely seen in the UK. So if you are curious to know what they represent, here they are (Note that measures represent US volume measures, which all differ from UK volume measures.).
- 1 cup, measuring = 8 fluid ounces (exactly) = ½ liquid pint (exactly)
- 1 tablespoon, measuring = 3 teaspoons (exactly) = 4 fluid drams = ½ fluid ounce (exactly)
NIST provides the following caution of the ‘teaspoon’:
“The equivalent ‘1 teaspoon = 1 1/3 fluid drams’ has been found by the Bureau to correspond more closely with the actual capacities of ‘measuring’ and silver teaspoons than the equivalent ‘1 teaspoon = 1 fluid dram’, which is given by a number of dictionaries.” Dram is the US spelling of the British drachm.
The US is far behind the UK in metrication so you are bound to find a lot of alien measurement units still used in the USA that have long been abandoned in the UK.
As well as all the measurement units mentioned in this article, the NIST document mentions the rod, pole, perch, furlong (now confined to horse racing in the UK), link, Gunter’s or surveyors chain (now confined to railways in the UK), gill, quart, minim, dram, peck, grain, pennyweight, scruple, quarter, fathom and league. Most of these units will be unfamiliar to young Britons.
Are you baffled by the system of US customary units? They are really complex and cumbersome to work with. When imperialists defend the use of imperial units in the UK because of US usage, do they really know all the strange features of US customary units? I guess not. Clearly the US is not an ideal model for our usage of measurement.
*An example is the article by Martin Geissler, a reporter for ITV News, published in the Evening Standard on Tuesday 8 November but clearly written earlier in Ohio, headed ‘Crushed hopes and anger in the Rust Belt: this is how Trump could win’.