English units are the historical units of measurement used in England up to 1824, which evolved as a combination of the Anglo-Saxon and Roman systems of units. They were redefined in the United Kingdom 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 International System of Units as a 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, or to the US customary system of unit. The common term used in the UK for the non-metric system is imperial units or imperial measurements, since they were used as a standard throughout the British Empire and the Commonwealth.
Various standards have applied to English units at different times, in different places, and for different applications.
Very little is known of the measurement units of the British Isles prior to Roman colonization in the 1st century CE. During the Roman period, Roman Britain relied on Ancient Roman units of measurement. During the Anglo-Saxon period, the North German foot of 335 millimetres (13.2 inches) was the nominal basis for other units of linear measurement. The foot was divided into 4 palms or 12 thumbs. A cubit was 2 feet, an elne 4 feet. The rod was 15 Anglo-Saxon feet, the furlong 10 rods. An acre was 4 × 40 rods, i.e., 160 square rods or 36,000 square Anglo-Saxon feet. However, Roman units continued to be used in the construction crafts. From the time of Offa King of Mercia (8th century) until 1526 the Saxon pound, also known as the moneyers' pound (and later known as the Tower pound) was the fundamental unit of mass measurement.
Prior to the enactment of a law known as the Composition of Yards and Perches (Compositio ulnarum et perticarum) some time between 1266 and 1303, the English system of measurement had been based on that of the Anglo-Saxons, inherited from tribes from northern Germany. The Compositio retained the Anglo-Saxon rod of 5.03 metres and the acre of 4 × 40 rods. However, it redefined the yard, foot, inch, and barleycorn to 10⁄11 of their previous value. Thus, the rod went from 5 old yards to 5 1⁄2 new yards, or 15 old feet to 16 1⁄2 new feet. The furlong went from 600 old feet (200 old yards) to 660 new feet (220 new yards). The acre went from 36,000 old square feet to 43,560 new square feet. Scholars have speculated that the Compositio may have represented a compromise between two earlier systems of the units, the Anglo-Saxon and the Roman.
Contrary to popular belief, the Norman conquest of England had little effect on British weights and measures other than to introduce one new unit: the bushel. William the Conqueror, in one of his first legislative acts, confirmed existing Anglo-Saxon measurement, a position which was consistent with Norman policy in dealing with occupied peoples. Another popular myth is that the Magna Carta of 1215 (specifically chapter 35) had any significant effect on English weights and measures, as this document only mentions one unit (the London Quarter) but does not define it.
Later development of the English system continued by defining the units by law and issuing measurement standards. 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 redefined by the international yard and pound agreement 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.
- about 1⁄4 of a barleycorn
- 1⁄4 of a barleycorn
- Smallest Anglo-Saxon unit of length. Notionally the length of a corn of barley, its actual length was determined in relation to a particular rod of metal, typically a yard-bar, and thus 1/108th of a yard, 1/36 of foot, or 1/3 of an inch. The unit was nominally the base unit from which the inch was defined. 3 barleycorns comprising 1 inch was the legal definition of the inch in many medieval 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 US 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:
less than 13 barleycorns = infants with no shoes; 13 to 26 barleycorns = children's sizes 1 to 12; 26 to 39 barleycorns = men's sizes 1 to 13.[clarification needed]
- 3⁄4 inch
- 7⁄8 inch
- 4 inches
- Ynch, inch
- Anglo Saxon inch, 3 barleycorns.
- 3 digits = 2 1⁄4 inches = 1⁄16 yard
- 3 inches
- Width of the hand and outstretched thumb, 6 1⁄2 ynches before 1066, 6 inches thereafter
- 7.92 inches or one 100th of a chain.
- Width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 3 palms = 9 inches
- Prior to the Anglo-Saxon invasions, the Roman foot of 11.65 inches (296 mm) was used. The Anglo-Saxons introduced a North-German foot of 13.2 inches (335 mm), divided into 4 palms or 12 thumbs, while the Roman foot continued to be used in the construction crafts. In the late 13th century, the modern foot of 304.8 mm was introduced, equal to exactly 10/11 Anglo-Saxon foot.
- From fingertips to elbow, 18 inches.
- 3 feet = 36 inches.
- From fingertip of outstretched arm to opposite shoulder, 20 nails = 1 1⁄4 yard or 45 inches. Mostly for measuring cloth
- Distance fingertip to fingertip arms outstretched, 6 feet
- Rod (= perch) (= pole)
- Used for surveying land and in architecture. The rod is the same length today as in Anglo-Saxon times. It is 16 1/2 feet long. The pole is commonly used as a measurement for Allotment Gardens. (See also perch as an area and a volume unit.)
- 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), nominally the distance a plough team could be driven without rest, it was actually a very precise measure of 40 rods or 600 Anglo-Saxon feet (ten percent longer than the modern foot). Thus, 660 modern 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.
- 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 Scotland 6,150 square yards and in Ireland 7,840 square yards. It is a Saxon unit, meaning field. Traditionally said to be "as much area as could be ploughed in one day".
- 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.
- 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.
- 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.
- an area equal to one square rod. (See also perch as a length and volume unit.)
- the amount of land a pair of oxen can plough in a single year. Approximately 30 acres (also called yard land).
Administrative units 
- 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.
- 60 minim or drops or 1⁄8 fluid ounce (fl. oz.)
- 80 minim or drops or 1⁄6 fl. oz.
- Tablespoon or mouthful
- 4 dram, 3 teaspoons or 1⁄2 fl. oz.
- 6 dram or 3⁄4 fl. oz.
- 3 tablespoons, 2 pony or 1.5 fl. oz.
- Jack or jackpot
- 5 tablespoons or 2.5 fl. oz. (double this for milk and beer in Northern England)
- 2 jack or 5 fl. oz. (or double this for milk and beer in Northern England)
- 2 gill or 10 fl. oz.
- 2 cup or 20 fl. oz. ("A pint of pure water weighs a pound and a quarter")
- 2 pint, 40 fl. oz. or 1⁄4 gallon
- 2 quart, 80 fl. oz or 1⁄2 gallon
- 2 pottle, 4 quarts or 160 fl. oz.
Dry goods 
- Dry gallon
- 4 dry quarts or 8 dry pints
- 2 dry gallons
- 2 peck or 4 dry gallons
- 2 kenning, 4 pecks or 8 dry gallons
- 2 bushels or 16 dry gallons
- Coomb or dry barrel
- 2 strike, 4 bushels or 32 dry gallons
- Dry hogshead
- 2 Coomb, 64 dry gallons or 1⁄4 dry tun
|1 tablespoon =||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||1⁄1024||1⁄2048||1⁄4096||1⁄8192||1⁄16384||1⁄32768||–8|
|1 pony =||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||1⁄1024||1⁄2048||1⁄4096||1⁄8192||1⁄16384||–7|
|1 jack =||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||1⁄1024||1⁄2048||1⁄4096||1⁄8192||–6|
|1 gill =||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||1⁄1024||1⁄2048||1⁄4096||–5|
|1 cup =||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||1⁄1024||1⁄2048||–4|
|1 pint =||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||1⁄1024||–3|
|1 quart =||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||–2|
|1 pottle =||128||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||–1|
|1 gallon =||256||128||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||0|
|1 peck =||512||256||128||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1|
|1 kenning =||1,024||512||256||128||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||2|
|1 bushel =||2,048||1,024||512||256||128||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||3|
|1 strike =||4,096||2,048||1,024||512||256||128||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||4|
|1 coomb =||8,192||4,096||2,048||1,024||512||256||128||64||32||16||8||4||2||1||1⁄2||1⁄4||5|
|1 hogshead =||16,384||8,192||4,096||2,048||1,024||512||256||128||64||32||16||8||4||2||1||1⁄2||6|
|1 butt/pipe =||32,768||16,384||8,192||4,096||2,048||1,024||512||256||128||64||32||16||8||4||2||1||7|
Specific goods 
- Oil barrel
- 35 gallons (or 42 wine gallons)
- 24.75 cubic feet of dry stone, derived from the more commonly known perch, a unit of length equal to 16.5 feet.
- 128 cubic feet of firewood, a stack of firewood 4 ft. × 4 ft. × 8 ft.
Ale, beer and liquids 
- 4.5 gallons or 1⁄8 beer barrel
- 2 pins, 9 gallons (ale, beer or goods) or 1⁄4 beer barrel
- 2 firkins, 18 gallons or 1⁄2 beer barrel
- Beer barrel
- 2 kilderkins, 36 gallons or 2⁄3 beer hogshead
- Beer hogshead
- 3 kilderkins, 54 gallons or 1.5 beer barrels
- Beer pipe or butt
- 2 beer hogsheads, 3 beer barrels or 108 gallons
- Beer tun
- 2 beer pipes or 216 gallons
|= 4.621 l||= 36.97 l||= 73.94 l||= 147.9 l||= 221.8 l|
|= 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|
|= 4.621 l||= 41.59 l||= 83.18 l||= 166.4 l||= 249.5 l|
|= 4.546 l||= 40.91 l||= 81.83 l||= 163.7 l||= 245.5 l|
Wine is traditionally measured based on the wine gallon established by Queen Anne in 1707. Defined as 231 cubic inches, it differs from the later imperial gallon, but is equal to the United States customary gallon.
- 18 wine gallons or 1⁄7 wine pipe
- Wine barrel
- 31.5 wine gallons or 1⁄2 wine hogshead
- 42 wine gallons, 1⁄2 puncheon or 1⁄3 wine pipe
- Wine hogshead
- 2 wine barrels, 63 wine gallons or 1⁄4 wine tun
- Puncheon or tertian
- 2 tierce, 84 wine gallons or 1⁄3 wine tun
- Wine pipe or butt
- 2 wine hogshead, 3 tierce, 7 roundlet or 126 wine gallons
- Wine tun
- 2 wine pipe, 3 puncheon or 252 wine gallons
|gallon||rundlet||barrel||tierce||hogshead||puncheon, tertian||pipe, butt||tun|
|1||1 1⁄2||3||puncheons, tertians|
|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)|
|1||15||26 1⁄4||35||52 1⁄2||70||105||210||gallons (imperial)|
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. This grain was legally defined as the weight of a grain seed from the middle of an ear of barley. There also was a smaller wheat grain, said to be 3⁄4 (barley) grains or about 48.6 milligrams.
- Grain (gr)
- 64.79891 mg, 1⁄7000 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: 'lb' stands for libra)
- 1⁄4 cwt
- Hundredweight (cwt)
- 112 lb
- 20 cwt
- 1⁄16 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 = 1⁄4 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.
- Grain (gr)
- = 64.79891 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
- 8 oz t
- Grain (gr)
- = 45⁄64 gr t ≈ 45.5 mg
- Pennyweight (dwt)
- 32 gr T = 22 1⁄2 gr t ≈ 1.46 g
- Tower ounce
- 24 dwt T = 640 gr T = 18 3⁄4 dwt t = 450 gr t ≈ 29 g
- Tower pound
- 12 oz T = 240 dwt T = 7680 gr T = 225 dwt t = 5400 gr t ≈ 350 g
- 8 oz T =
- Grain (gr)
- = 64.79891 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.
|Avoirdupois||1||175⁄144||35⁄27||28⁄27||35⁄36||16||14 7⁄12||15 5⁄9||7000||9955 5⁄9||454||10⁄22|
|Troy||144⁄175||1||16⁄15||64⁄75||4⁄5||13 29⁄175||12||12 4⁄5||5760||8192||373||3⁄8|
|Tower||27⁄35||15⁄16||1||4⁄5||3⁄4||12 12⁄35||11 1⁄4||12||5400||7680||350||7⁄20|
|Merchant||27⁄28||75⁄64||5⁄4||1||15⁄16||15 3⁄7||14 1⁄16||15||6750||9600||437||7⁄16|
See also 
- Marks' Standard Handbook for Mechanical Engineers, McGraw Hill, 2006
- Zupko, Ronald Edward (1977). British Weights and Measures: A History from Antiquity to the Seventeenth Century. University of Wisconsin Press. pp. 20–21. ISBN 978-0-299-07340-4.
- "poppyseed". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005.
- H. Arthur Klein (1974). The world of measurements: masterpieces, mysteries and muddles of metrology. New York: Simon and Schuster. p. 63.
- Zupko, Ronald Edward (1977). British Weights and Measures: A History from Antiquity to the Seventeenth Century. University of Wisconsin Press. p. 21. ISBN 978-0-299-07340-4.
- Tax, Herman (1985). Podopediatrics. Baltimore, MD: Williams and Wilkins. p. 386. ISBN 0-683-08118-7.
- Merriam Webster Online Dictionary, Link definition
- Blocksma, Mary. Reading the Numbers. New York: Penguin Books, 1989.
- "cord, n 1". Oxford English Dictionary (2 ed.). Oxford, England: Oxford University Press. 1989. "from Richard Boyle, 1616"
- Unwin, Tim (1991). Wine and the Vine. London: Routledge. p. 364. ISBN 0-415-14416-7.
- English Customary Weights and Measures
- Jacques J. Proot's Anglo-Saxon weights & measures page. Internet Archive Wayback Machine
- Alexander Justice, "A General Discourse of the Weights and Measures" (London, 1707).