English units

The term English units refers to one of a number of systems of units of measurement, some obsolete, and some still in use. In spite of the name, it does not necessarily refer to the (non-SI) system of units still in intermittent use in England itself. In fact, the latter is often referred to outside the United States as the Imperial System.

Various different standards under the name 'English units' have applied at different times, in different places and for different things. Prior to the Battle of Hastings in 1066 the Anglo-Saxon system of measurement had been based on the units of the barleycorn and the gyrd (rod). This system presumably had Germanic origins. After the Norman conquest Roman units were reintroduced. The resultant system of English units was a combination of the Anglo-Saxon and Roman systems.

Later development of the British system continued by defining the units by law in the Magna Carta of 1215, and issuing measurement standards from the then capital Winchester. Standards were renewed in 1496, 1588 and 1758. The last Imperial Standard Yard in bronze was made in 1845; it served as the standard in the United Kingdom until the yard was internationally redefined as 0.9144 metre in 1959 (statutory implementation: Weights and Measures Act of 1963).

The use of English units spread throughout the British Isles and to the British colonies. These units form the basis for the Imperial system formerly used in Commonwealth countries and U.S. customary system used in the US. However, there exist differences between the U.S. customary system and the Imperial system the former being based on English systems of the 1700s whilst the latter being defined in 1824 after the American colonies had declared independence.

In the form of the U.S. customary system English units are still very much in use in the United States despite official adoption of the International System of units (SI). In contrast, the use of these units in Commonwealth countries, where the introduction of the SI has been more successful, is limited and declining.

Historical English units

Length

poppyseed

¼ of a barleycorn

barleycorn

Basic Anglo-Saxon unit, the length of a corn of barley. The unit survived after 1066, redefined as 1/3 inch. Note the relation to the grain unit of weight.

digit

¾ inch

finger

7/8 inch

ynch, inch

Anglo Saxon inch, 3 barleycorns. Based on the Roman uncia from 1066.

nail

3 digits = 2¼ inches = 1/16 yard

palm

3 inches

hand

4 inches

shaftment

Width of the hand and outstretched thumb, 6½ ynches before 1066, 6 inches thereafter

span

Width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 3 palms = 9 inches

foot

Usually 13 ynches but also other variants. Shortened by basing it on the Roman pes from 1066.

cubit

Forearm, 18 inches

yard

Introduced after 1066, 3 feet = 36 inches.

ell

Elbow, 20 nails = 1¼ yard or 45 inches. Mostly for measuring clothing

fathom

From one fingertip to the other, 6 feet

rod

Saxon gyrd measuring stick, might have been from 20 "natural feet". Retained its length but redefined as 16 ½ Roman feet after 1066.

furlong

"Furrow long" (Saxon furrow is fuhr), probably based on the ancient Mediterranean stadion, defined as 40 rods

mile

Introduced after 1066, originally the Roman mile at 5000 feet, in 1592 it was extended to 5280 feet to make it an even number of furlongs, i.e. 8.

league

Usually three miles. Intended to be an hour's walk.

chain

Any of several actual chains used for land surveying and divided in links. Gunter's chain, introduced in the 17th century, is 66 feet.

Area

acre

Saxon unit, meaning "field", one furlong by 4 rods. Probably meant to be "as much area as could be plowed in one day".

Volume

General

In both Britain and America, in addition to perch as a measure of length, there is also the perch which refers to the volume measurement of stone; one perch is equal to 16.5 ft × 1.5 ft × 1 ft = 24.75 cu. ft. of dry stone. The relationship to the unit of length (one perch = 16.5 feet) should be obvious.

Wine

English wine cask units

gallon	rundlet	barrel	tierce	hogshead	puncheon, tertian	pipe, butt	tun
							1	tun
						1	2	pipes, butts
					1	1+1⁄2	3	puncheons, tertians
				1	1+1⁄3	2	4	hogsheads
			1	1+1⁄2	2	3	6	tierces
		1	1+1⁄3	2	2+2⁄3	4	8	barrels
	1	1+3⁄4	2+1⁄3	3+1⁄2	4+2⁄3	7	14	rundlets
1	18	31+1⁄2	42	63	84	126	252	gallons (wine)
3.785	68.14	119.24	158.99	238.48	317.97	476.96	953.92	litres
1	15	26+1⁄4	35	52+1⁄2	70	105	210	gallons (imperial)
4.546	68.19	119.3	159.1	238.7	318.2	477.3	954.7	litres

Brewery

English brewery cask units

gallon	firkin	kilderkin	barrel	hogshead		Year designated
				1	hogsheads
			1	1+1⁄2	barrels
		1	2	3	kilderkins
	1	2	4	6	firkins
1	8	16	32	48	ale gallons	(1454)
= 4.621 L	= 36.97 L	= 73.94 L	= 147.9 L	= 221.8 L
1	9	18	36	54	beer gallons
= 4.621 L	= 41.59 L	= 83.18 L	= 166.4 L	= 249.5 L
1	8+1⁄2	17	34	51	ale gallons	1688
= 4.621 L	= 39.28 L	= 78.56 L	= 157.1 L	= 235.7 L
1	9	18	36	54	ale gallons	1803
= 4.621 L	= 41.59 L	= 83.18 L	= 166.4 L	= 249.5 L
1	9	18	36	54	imperial gallons	1824
= 4.546 L	= 40.91 L	= 81.83 L	= 163.7 L	= 245.5 L

Weight

The Avoirdupois, Troy and Apothecary systems of weights all shared the same finest unit, the grain, however they differ as to the number of grains there are in a dram, ounce and pound. Originally, this grain was the weight of a grain seed from the middle of an ear of barley. There also was a smaller wheat grain, said to be ¾ (barley) grains or about 48.6 milligrams.

Avoirdupois

grain (gr)

≈ 65 mg

dram/drachm (dr)

27.34375 gr (sixteenth of an ounce) (possibly originated as the weight of silver in ancient greek coin drachma)

ounce (oz)

16 dr = 437.5 grains ≈ 28 g

pound (lb)

16 oz = 7000 grains ≈ 454 g

quarter

¼ cwt

hundredweight (cwt)

112 lb (long) or 100 lb (short)

ton

20 cwt

Additions:

nail

1/16 cwt = 7 lb

clove

7 lb (wool)

stone (st)

2 cloves = 14 lb (an Anglo-Saxon unit changed to fit in)

tod

2 st = ¼ cwt (long)

Troy

grain (gr)

≈ 65 mg

pennyweight (dwt)

24 gr ≈ 1.56 g

ounce (oz t)

20 dwt = 480 gr ≈ 31.1 g

pound (lb t)

12 oz t = 5760 gr ≈ 373 g

Tower

tower ounce

18¾ dwt = 450 gr ≈ 29 g

tower pound

12 oz T = 225 dwt = 5400 gr ≈ 350 g

The Troy and Tower pounds and their subdivisions were used for coins and precious metals. The Tower pound, which is based upon an earlier Anglo-Saxon pound, was abolished in 1527.

In terms of (silver) currency a pound was 20 shillings of 12 pennies each (i.e. 240) from the late 8th century (Charlemagne/Offa of Mercia) to 1971 in Great Britain, but lighter than a troy one.

Apothecary

grain (gr)

≈ 65 mg

scruple (s ap)

20 gr

dram (dr ap)

3 s ap = 60 gr

ounce (oz ap)

8 dr ap = 480 gr

pound (lb ap)

5760 gr = 1 lb t

Others

Merchants/Mercantile pound

15 oz tower = 6750 gr ≈ 437.4 g

London/Mercantile pound

15 oz troy = 16 oz tower = 7200 gr ≈ 466.6 g

Mercantile stone

12 lb L ≈ 5.6 kg

Tron pound (Edinburgh/Scots)

16 oz Tron ≈ 623.5 g

Butcher's stone

8 lb ≈ 3,63 kg

Sack

26 st = 364 lb ≈ 165 kg

The carat was once specified as four grains in the English-speaking world. Some local units in the English dominion were (re-)defined in simple terms of English units, such as the Indian tola of 180 grains.

English pounds

	Pounds					Ounces			Grains	Metric
Pound	av.lb.	tr.lb.	T.lb.	m.lb	L.lb.	av.oz.	tr.oz.	T.oz.	gr.	g	ca. kg
Avoirdupois	1	175/144	35/27	28/27	35/36	16	14 7/12	15 5/9	7000	454	9/20
Troy / Ap.	144/175	1	16/15	64/75	5/6	13 29/175	12	12 4/5	5760	373	3/8
Tower	27/35	15/16	1	4/5	3/4	12 12/35	11 1/4	12	5400	350	7/20
Merchant	27/28	75/64	5/4	1	15/16	15 3/7	14 1/16	15	6750	437	7/16
London	36/35	6/5	4/3	16/15	1	16 16/35	15	16	7200	467	7/15

See also: slug and poundal.

Scottish system

Length

• inch – 2.554 cm
• foot – 12 inches, 30.645 cm
• ell – Elbow, 37 Scots inches. 94.5 cm
• fall – 18 Scots feet
• mile – 320 falls, 1814.2 m

Comparison of the Imperial and US customary systems

Volume

The Imperial gallon (4.546 09 L) and bushel (36.368 72 L) are, respectively, about 20 per cent and 3 per cent larger than the United States liquid gallon (3.785 411 784 L) and bushel (35.239 070 166 88 L). The Imperial gallon was originally defined as the volume of 10 avoirdupois pounds of water under specified conditions, and the Imperial bushel was defined as 8 Imperial gallons. Also, the subdivision of the Imperial gallon as presented in the table of British apothecaries' fluid measure differed in two important respects from the corresponding United States subdivision, in that the Imperial gallon was divided into 160 fluid ounces (whereas the United States gallon is divided into 128 fluid ounces), and a "fluid scruple" is included.

The origins of these differences lie in the variety of systems that were in use in Britain at the time of the establishment of the first colonies in North America. The American colonists adopted the English wine gallon of 231 cubic inches, and used it for all fluid purposes. The English of that period used this wine gallon, but they also had another gallon, the ale gallon of 282 cubic inches. In 1824, the British abandoned these two gallons when they adopted the British Imperial gallon, which they defined as the volume of 10 pounds of water, at a temperature of 62 °F, weighed in air with brass weights, which, by calculation, is equivalent to about 277.42 cubic inches (4,546.1 cm³)—much closer to the ale gallon than the wine gallon. At the same time, they redefined the bushel to be 8 gallons.

As noted above, in the customary British system the units of dry measure are the same as those of liquid measure. In the United States these two are not the same, the gallon and its subdivisions are used in the measurement of liquids; the bushel, with its subdivisions, is used in the measurement of certain dry commodities. The U.S. gallon (3.785 411 784 L) is divided into four liquid quarts (946.352 946 mL each) and the U.S. bushel (35.239 070 166 88 L) into 32 dry quarts (1.101 220 942 715 L each) or 4 pecks (8.809 767 541 72 L each). All the units of capacity or volume mentioned thus far are larger in the Imperial system than in the U.S. system (by about 20% for wet measures). But the British fluid ounce is smaller than (about 96% of) the U.S. fluid ounce, because the British quart is divided into 40 fluid ounces whereas the U.S. quart is divided into 32 fluid ounces.

From this we see that, in the Imperial system, an avoirdupois ounce of water at 62 °F has a volume of one fluid ounce, because 10 pounds is equivalent to 160 avoirdupois ounces, and 1 Imperial gallon is equivalent to 4 Imperial quarts, or 160 fluid ounces. This convenient relation does not exist in the U.S. system because a U.S. gallon of water at 62 °F weighs about 8 1/3 pounds, or 133 1/3 avoirdupois ounces, and the U.S. gallon is equivalent to 4 × 32, or 128 fluid ounces.

Comparison of Imperial and U.S. volume measures

1 U.S. fluid ounce	= 29.573 529 562 5 mililitres	≈ 1.041 Imperial fluid ounces
1 Imperial fluid ounce	= 28.413 062 5 mililitres	≈ 0.961 U.S. fluid ounce
1 liquid U.S. gallon	= 3.785 411 784 litres	≈ 0.833 Imperial gallon
1 Imperial gallon	= 4.546 09 litres	≈ 1.201 liquid U.S. gallons
1 dry U.S. gallon	= 4.404 842 803 2 litres	≈ 0.968 Imperial gallon
1 Imperial gallon	= 4.546 09 litres	≈ 1.032 dry U.S. gallons

In the apothecary system of liquid measure the British add a unit, the fluid scruple, equal to one third of a fluid drachm (spelt dram in the United States) between their minim and their fluid drachm.

Length

The international yard is defined in terms of the metric system of units to be exactly 0.9144 m. This definition was agreed upon by the U.S., Canada, the U.K., South Africa, Australia and New Zealand in 1959. However, the U.S. continued to use its previous national definition of the length units for surveying purposes.

The U.S. survey foot is defined so that 1 metre is exactly 39.37 inches; the international foot is exactly two parts per million shorter. The U.S. survey foot and survey mile have been maintained as separate units for surveying purposes. This was done to avoid the accumulation of error it would entail replacing them with the international versions. This was not a problem for the United Kingdom, as the Ordnance Survey has been metric since before World War II.

The main units of length (inch, foot, yard and international mile) were the same in the USA, though some of the intermediate units such as the (surveyor's) chain (22 yards) and the furlong (220 yards) were hardly used there.

At one time the nautical mile was defined differently in the U.K. and the U.S. however today both countries use the international definition of 1852 metres. For more details refer to the Nautical mile article.

Weight

A discussion of differences between countries is complicated by the fact that both Britain and the U.S. have made some use of three different weight systems, troy weight, used for precious metals, avoirdupois weight, used for most other purposes, and apothecaries' weight, now virtually unused since the metric system is used for all scientific purposes.

Among other differences between the customary British and the United States measurement systems, we should note that the use of the troy pound (373.241 721 6 g) was abolished in Britain on January 6, 1879, with only the troy ounce (31.103 476 8 g) and its decimal subdivisions retained, whereas the troy pound (of 12 troy ounces) and pennyweight are still legal in the United States, although they are not now greatly used. Another important difference is the universal use in Britain, for body weight, of the stone of 14 pounds (6.350 293 18 kg), this being a unit now unused in the United States, although its influence was shown in the practice until World War II of selling flour by the barrel of 196 pounds (14 stone).

In all the systems, the fundamental unit is the pound, and all other units are defined as fractions or multiples of it. The tables of Imperial troy mass and apothecaries' mass are the same as the corresponding United States tables, except for the British spelling "drachm" in the table of apothecaries' mass. The table of Imperial avoirdupois mass is the same as the United States table up to 1 pound, above that point the table differs.

The Imperial system uses a hundredweight of eight stone or 112 lb (50.802 345 44 kg) whereas a U.S. hundredweight is 100 lb (45.359 237 kg). In both systems 20 hundred weights make a ton. In the U.S. the terms long ton (2240 lb, 1016.046 908 8 kg) and short ton (2000 lb, 907.184 74 kg) are used to distinguish them. The term metric ton is also used to denote a tonne (1000 kg).

references

• Colin Renfrew and Paul Bahn Template:Section:Book reference after author
• George Bass Template:Section:Book reference after author
• William H McNeil and Jean W Sedlar Template:Section:Book reference after author
• Andrew George Template:Section:Book reference after author
• James B. Pritchard Template:Section:Book reference after author
• Shaika Haya Ali Al Khalifa and Michael Rice Template:Section:Book reference after author
• Muhammed Abdul Nayeem Template:Section:Book reference after author
• Marie-Loise Thomsen Template:Section:Book reference after author
• Michael Roaf Template:Section:Book reference after author
• Chang Template:Section:Book reference after author
• Nicholas Awde and Putros Samano Template:Section:Book reference after author
• Gardiner Template:Section:Book reference after author
• Antonio Loprieno Template:Section:Book reference after author
• Michael Rice Template:Section:Book reference after author
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• Somers Clarke and R. Englebach Template:Section:Book reference after author
• J. P. Mallory Template:Section:Book reference after author
• Nelson GlueckTemplate:Section:Book reference after author
• Anne H. Groton Template:Section:Book reference after author
• Hines Template:Section:Book reference after author
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• Claudias Ptolemy Template:Section:Book reference after author
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• Silvia Luraghi Template:Section:Book reference after author
• Michael Grant Template:Section:Book reference after author
• Alex Patterson Template:Section:Book reference after author
• Lucas N. H. Bunt, Phillip S. Jones, Jack D. Bedient Template:Section:Book reference after author
• H. Arthur Klein Template:Section:Book reference after author
• R. A. Cordingley Template:Section:Book reference after author
• Jean Gimpel Template:Section:Book reference after author
• Lionel Casson Template:Section:Book reference after author
• Francis H. Moffitt Template:Section:Book reference after author
• Brian M. Fagan Template:Section:Book reference after author
• H. Johnathan Riley Smith Template:Section:Book reference after author
• Elizabeth Hallam Template:Section:Book reference after author
• H. W. Koch Template:Section:Book reference after author
• Measure for Measure, Richard Young and Thomas Glover, ISBN 1-889796-00-X.

See also

• Weights and measures
• Historical weights and measures
• Imperial unit
• U.S. customary unit
• Metrified English unit
• Approximate conversion between English and SI units
• SI

External link

• English Customary Weights and Measures