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English units refers to the historical units of measurement in medieval Englandmarker, which evolved as a combination of the Anglo-Saxon and Roman systems of units. They were redefined in England in 1824 by a Weights and Measures Act, which retained many but not all of the unit names with slightly different values, and again in the 1970s by the SI subset of the Metric system. In modern UK usage, the term is considered ambiguous, as it could refer either to the imperial system used in the UK prior to metrication, or to the US customary system of unit. The usual term used in the UK for the system immediately prior to metrication is imperial units.

Within the United States, the same term is commonly used to refer to the United States Customary System, which retains some unit names but with different values, as well as to the imperial units.

Various standards under the name English units have applied at different times, in different places and for different things. Prior to the Battle of Hastingsmarker in 1066 the Anglo-Saxon system of measurement had been based on the units of the barleycorn and the gyrd (rod), inherited from tribes from Germanymarker. 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 English system continued by defining the units by law in the Magna Carta of 1215, and issuing measurement standards from the then capital Winchestermarker. 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 Kingdommarker until the yard was internationally redefined as 0.9144 metre in 1959 (statutory implementation: Weights and Measures Act of 1963). The English system then spread to other parts of the British Empire.


Chart showing the relationships of distance measures.
about of a barleycorn
of a barleycorn
Basic Anglo-Saxon unit, the length of a corn of barley. The unit survived after 1066, as the base unit from which the inch was nominally defined. 3 barleycorns comprising 1 inch was the legal definition of the inch in many mediæval laws, both of England and Wales, from the 10th century Laws of Hywel Dda to the 1324 definition of the inch enacted by Edward II. Note the relation to the grain unit of weight. This archaic measure is still the basis for current UK and U.S. shoe sizes, with the largest shoe size taken as thirteen inches (a size 13) and then counting backwards in barleycorn units, although the original derivation was
4 inches
ynch, inch
Anglo Saxon inch, 3 barleycorns. Based on the Roman uncia from 1066.
3 digits = inches = yard
3 inches
Width of the hand and outstretched thumb, ynches before 1066, 6 inches thereafter
Width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 3 palms = 9 inches
Usually 13 inches but also other variants. Shortened to 12 inches by basing it on the Roman pes from 1066.
From fingertips to elbow, 18 inches.
Introduced after 1066, 3 feet = 36 inches.
From fingertip of outstretched arm to opposite shoulder, 20 nails = yard or 45 inches. Mostly for measuring cloth
Distance fingertip to fingertip arms outstretched, 6 feet
Measurement of land, might have been from 20 "natural feet". Retained its length but redefined as feet after 1066.
four linear rods. Named after the length of surveyor's chain used to measure distances until quite recently. Any of several actual chains used for land surveying and divided in links. Gunter's chain, introduced in the 17th century, is 66 feet.
"One plough's furrow long" (Saxon furrow is furh), the distance a plough team could be driven without rest. This varied from region to region depending on soil type and local habit. In modern context, it is deemed to be 660 feet, 40 rods or ten chains.
Introduced after 1066, originally the Roman mile at 5000 feet, in 1592 it was extended to 5280 feet to make it an even number (8) of furlongs.
Usually three miles. Intended to be an hour's walk.


perch: one rod, when referring to length; one square rod when referring to area; one rod by one foot by a foot and a half when referring to volume (usually specifically for masonry stonework)
acre: area of land one chain (four rods) in width by one furlong in length. As the traditional furlong could vary in length from country to country, so did the acre. In England an acre was 4,840 square yards, in Scotlandmarker 6,150 square yards and in Ireland 7,840 square yards. It is a Saxon unit, meaning field. Probably meant to be "as much area as could be ploughed in one day".
rood: one quarter of an acre, confusingly sometimes called an acre itself in many ancient contexts. One furlong in length by one rod in width, or 40 square rods.
carucate: an area equal to that which can be ploughed by one eight-oxen team in a single year (also called a plough or carve). Approximately 120 acres.
bovate: the amount of land one ox can plough in a single year (also called an oxgate). Approximately 15 acres or one eighth of a carucate.
virgate: the amount of land a pair of oxen can plough in a single year. Approximately 30 acres (also called yard land).

Administrative units

hide: four to eight bovates. A unit of yield, rather than area, it measured the amount of land able to support a single household for agricultural and taxation purposes.
knight's fee: five hides. A knight's fee was expected to produce one fully equipped soldier for a knight's retinue in times of war.
hundred: or wapentake - 100 hides grouped for administrative purposes.



Mouthful: about Ounce
Pony: Mouthful × 2 = 1 oz.
Jigger: 1.5 oz.
Jack or Jackpot: Jigger × 2 = 2 oz.
Gill: Jack × 2 = 4 oz (U.S.) or 5 oz (imperial).
Cup: Gill × 2 = 8 oz.
Cup × 2 = 16 oz. (U.S.) or 20 oz (imperial) (and a "Pint's a pound the world around" or in the United Kingdom, "A pint of pure water weighs a pound and a quarter")
Chart showing the relationships of volume measures.
Quart: Pint × 2 = 32 oz. (U.S.) or 40 oz (imperial)
Pottle or Half Gallon: Quart × 2 = 64 oz. (U.S.) or 80 oz (imperial) or 1 gallon.
Gallon: Pottle × 2 = 4 Quarts = 128 oz. (U.S.) or 160 oz (imperial). A US gallon is defined as 231 cubic inches (exactly).
Peck: Gallon × 2
Kenning or Pail: Peck × 2 = 4 gal.
Bushel: Kenning × 2 = 8 gal.
Strike: Bushel × 2 = 16 gal.
Coomb: Strike × 2 = 32 gal.
Cask: Coomb × 2 = 64 gal.
Barrel: Cask × 2 = 32 gal.
Hogshead: Barrel × 2 = 64 gal.
Butt or Pipe: hogshead × 2 = 128 gal.
Tun: Butt × 2 = 256 gal. (A tun is a ton). A Tun would actually be about 2,048 lb. but is a pretty close estimate, given that you would derive the weight and volume all from mouthfuls of water.
In both the United Kingdom 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.
128 cubic feet of firewood; a stack of firewood 4 ft × 4 ft × 8 ft.




Chart showing the relationships of weight measures.
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 (barley) grains or about 48.6 milligrams.


grain (gr)
64.79891 mg, of a pound
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 (NB
hundredweight (cwt)
112 lb (long) or 100 lb (short)
20 cwt
cwt = 7 lb
7 lb (wool) or 8 lb (cheese)
stone (st)
2 cloves = 14 lb (an Anglo-Saxon unit changed to fit in)
2 st = cwt (long)

Troy and Tower

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 the United Kingdom, but lighter than a troy one. Most old European currencies, like mark, shilling/solidus/groschen/øre, penny/pfennig/denar, taler/dollar/krone, florin/gulden/guilder/pound/złoty also belong into this monetary system.


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
mark: 8 oz t


tower ounce
dwt = 450 gr ≈ 29 g
tower pound
12 oz T = 225 dwt = 5400 gr ≈ 350 g


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


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

Butcher's stone
8 lb ≈ 3.63 kg
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.

See also


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