English units are the units of measurement used in England up to 1826 (when they were replaced by Imperial units), which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications.
The two main sets of English units were the Winchester Units, used from 1495 to 1587, as affirmed by King Henry VII, and the Exchequer Standards, in use from 1588 to 1825, as defined by Queen Elizabeth I.
The English units were replaced by Imperial units in 1824 (effective 1 January 1826) by a Weights and Measures Act, which retained many though not all of the unit names and redefined (standardised) many of the definitions.
Use of the term "English units" can be ambiguous, as, in addition to the meaning used in this article, it is sometimes used to refer to the units of the descendent Imperial system as well to those of the descendant system of United States customary units.
Very little is known of the measurement units of the British Isles prior to Roman colonisation in the 1st century AD. During the Roman period, Roman Britain relied on Ancient Roman units of measurement. During the Anglo-Saxon period, the North German foot of 13.2 inches (335 millimetres) 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, and reckoning by the Roman mile of 5,000 feet (or 8 stades) continued, in contrast to other Germanic countries which adopted the name "mile" for a longer native length closer to the league (which was 3 Roman miles). 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 weight (by Offa's law, one pound of silver, by weight, was subdivided into 240 silver pennies, hence (in money) 240 pence - twenty shillings - was known as one pound).
Prior to the enactment of a law known as the "Composition of Yards and Perches" (Latin: Compositio ulnarum et perticarum) some time between 1266 and 1303, the English system of measurement had been based on that of the Anglo-Saxons, who were descended from tribes of northern Germany. The Compositio redefined the yard, foot, inch, and barleycorn to 10⁄11 of their previous value. However, it retained the Anglo-Saxon rod of 15 x 11⁄10 feet (5.03 metres) and the acre of 4 × 40 rods. 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 the two earlier systems of 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. The Magna Carta of 1215 stipulates that there should be a standard measure of volume for wine, ale and corn, the London Quarter, and for weight likewise, but does not define any units.
Later development of the English system was by defining the units in laws and by 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 metres) in 1959 (statutory implementation was in the Weights and Measures Act of 1963). Over time, the English system had spread to other parts of the British Empire.
Selected excerpts from the bibliography of Marks and Marking of Weights and Measures of the British Isles
|English unit||SI ('Metric')||Relationship|
|Poppyseed||2.12 or 1.69 mm||= 1⁄4 or 1⁄5 of a barleycorn|
|Line||2.12 mm||= 1⁄4 of a barleycorn|
|Barleycorn||8.47 mm||= 1⁄3 of an inch, the notional base unit under the Composition of Yards and Perches.|
|Digit||19.05 mm||= 3⁄4 inch|
|Finger||22.23 mm||= 7⁄8 inch|
|Inch||25.4 mm||= 3 barleycorns (the historical legal definition)|
|Nail||57.15 mm||= 3 digits = 2+1⁄4 inches = 1⁄16 yard|
|Palm||76.2 mm||= 3 inches|
|Hand||101.6 mm||= 4 inches|
|Shaftment||165 mm or 152 mm||= Width of the hand and outstretched thumb, 6+1⁄2 inches before 12th century, 6 thereafter|
|Link||201.2 mm||= 7.92 inches or one 100th of a Chain. (A modern Indian surveyor's chain has 200 mm links.)|
|Span||228.6||= Width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 3 palms = 9 inches.|
|Foot||304.8 mm||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.|
|Cubit||457.2 mm||From fingertips to elbow, 18 inches.|
|Yard||0.914 m||3 feet = 36 inches, the practical base unit, defined as the length of the prototype bar held by the Crown or Exchequer.|
|Ell||1.143 m||From fingertip of outstretched arm to opposite shoulder, 20 nails = 1+1⁄4 yard or 45 inches. Mostly for measuring cloth.|
|Fathom||1.829 m||= 6 feet, distance between arms outstretched, from fingertip to fingertip, on a 6-foot-tall person.|
|Rod||5 m||Also called a perch or pole: a measure used for surveying land and in architecture. The rod is the same length today as in Anglo-Saxon times, although its composition in terms of feet were changed by the Composition of Yards and Perches from 15 feet to 16+1⁄2 feet or 5+1⁄2 yards. The pole is commonly used as a measurement for Allotment gardens. (See also perch as an area and a volume unit.)|
|Chain||20.116 m||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 (20.1 metres).|
|Furlong||201.168 m||Notionally the distance a plough team could furrow without rest, but actually a measure of 40 rods or 600 feet prior to the Composition of Yards and Perches; 40 rods or 660 feet since then. (See also the Ancient Greek stadion or 'stade'.)|
|Mile||1.61 km||5280 feet or 1760 yards. Originally the Roman mile, reckoned as 5000 feet, 1000 paces, or 8 stades but adjusted to 5280 feet in 1593 to account for the differences introduced to these methods of reckoning by the Composition of Yards and Perches.|
|League||4.83 km||Notionally an hour's march, but usually reckoned as three miles. Approximate length of the traditional "mile" in German and Scandinavian countries.|
|English unit||SI ('Metric')||Relationship|
|Square rod||25.29 m2||=30.25 square yards. A square rod is also known as a square pole or a square perch. Sometimes the word 'square' is omitted when the context clearly indicates that the subject is area, notably so in the case of British allotment gardens.|
|Rood||1,012 m2||= one quarter of an acre; one 'furlong' in length by one 'rod' in width; 40 square 'rods'. The rood was sometimes called an acre itself in many ancient contexts.|
|= an area of land one 'chain' (four rods) wide 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 (4,050 m2), in Scotland 6,150 square yards (5,140 m2) and 7,840 square yards (6,560 m2) in Ireland. It is a Saxon unit, meaning field. Traditionally said to be "as much area as could be ploughed in one day".|
|Bovate||6 ha||= the amount of land one ox can plough in a single year (also called an oxgang). Approximately 15 acres or one eighth of a carucate.|
|Virgate||12 ha||= the amount of land a pair of oxen can plough in a single year. Approximately 30 acres (also called yard land).|
|Carucate||49 ha||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.|
Many measures of capacity were understood as fractions or multiples of a gallon. For example, a quart is a quarter of a gallon, and a pint is half of a quart, or an eighth of a gallon. These ratios applied regardless of the specific size of the gallon. Not only did the definition of the gallon change over time, but there were several different kinds of gallon, which existed at the same time. For example, a wine gallon with a volume of 231 cubic inches (the basis of the U.S. gallon), and an ale gallon of 282 cubic inches, were commonly used for many decades prior to the establishment of the imperial gallon. In other words, a pint of ale and a pint of wine were not the same size. On the other hand, some measures such as the fluid ounce were not defined as a fraction of a gallon. For that reason, it is not always possible to give accurate definitions of units such as pints or quarts, in terms of ounces, prior to the establishment of the imperial gallon.
|Minim||0.06 ml||Also known as a drop, though the volume of a drop is not well defined: it depends on the device and technique used to produce the drop, on the strength of the gravitational field, and on the viscosity, density, and the surface tension of the liquid.|
|Dram||3.55 ml||60 minims or 'drops' or 1⁄8 fluid ounce (fl oz). See also drachm.|
|Teaspoon||5 ml||80 minim or drops or 1⁄6 fl oz|
|Tablespoon||15 ml||4 dram (240 minim or drops), 3 teaspoons, or 1⁄2 fl oz|
|Jack||71 ml||1⁄2 Gill or 1⁄4 pint. This is not a traditional measure.|
|Gill||142 ml||1⁄4 pint, or 1⁄32 gallon, in some dialects 1⁄2 pint. Pronounced as "Jill"|
|Pint||568 ml||1⁄8 gallon|
|Quart||1.136 litre||2 pints or 1⁄4 gallon|
|Pottle||2.272 L||2 quarts or 1⁄2 gallon|
|Gallon||4.544 L||8 pints|
Liquid measures as binary submultiples of their respective gallons (ale or wine):
|1 jack =||1||1⁄2||1⁄8||1⁄16||1⁄32||1⁄64||–6|
|1 gill =||2||1||1⁄4||1⁄8||1⁄16||1⁄32||–5|
|1 pint =||8||4||1||1⁄2||1⁄4||1⁄8||–3|
|1 quart =||16||8||2||1||1⁄2||1⁄4||–2|
|1 pottle =||32||16||4||2||1||1⁄2||–1|
|1 gallon =||64||32||8||4||2||1||0|
Wine is traditionally measured based on the wine gallon and its related units. Other liquids such as brandy, spirits, mead, cider, vinegar, oil, honey, and so on, were also measured and sold in these units.
The wine gallon was re-established by Queen Anne in 1707 after a 1688 survey found the Exchequer no longer possessed the necessary standard but had instead been depending on a copy held by the Guildhall. Defined as 231 cubic inches, it differs from the later imperial gallon, but is equal to the United States customary gallon.
|gallon||rundlet||barrel||tierce||hogshead||puncheon, tertian||pipe, butt||tun|
|= 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|
|= 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|
The Winchester measure, also known as the corn measure, centered on the bushel of approximately 2,150.42 cubic inches, which had been in use with only minor modifications since at least the late 15th century. The word corn at that time referred to all types of grain. The corn measure was used to measure and sell many types of dry goods, such as grain, salt, ore, and oysters.
However, in practice, such goods were often sold by weight. For example, it might be agreed by local custom that a bushel of wheat should weigh 60 pounds, or a bushel of oats should weigh 33 pounds. The goods would be measured out by volume, and then weighed, and the buyer would pay more or less depending on the actual weight. This practice of specifying bushels in weight for each commodity continues today. This was not always the case though, and even the same market that sold wheat and oats by weight might sell barley simply by volume. In fact, the entire system was not well standardized. A sixteenth of a bushel might be called a pottle, hoop, beatment, or quartern, in towns only a short distance apart. In some places potatoes might be sold by the firkin—usually a liquid measure—with one town defining a firkin as 3 bushels, and the next town as 2 1/2 bushels.
The pint was the smallest unit in the corn measure. The corn gallon, one eighth of a bushel, was approximately 268.8 cubic inches. Most of the units associated with the corn measure were binary (sub)multiples of the bushel:
|1 pint =||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||–3|
|1 quart =||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||–2|
|1 pottle =||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||–1|
|1 gallon =||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||0|
|1 peck =||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1|
|1 kenning =||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||2|
|1 bushel =||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||3|
|1 strike =||128||64||32||16||8||4||2||1||1⁄2||1⁄4||4|
|1 coomb =||256||128||64||32||16||8||4||2||1||1⁄2||5|
|1 seam =||512||256||128||64||32||16||8||4||2||1||6|
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.
The avoirdupois pound contained 7,000 grains and was used for all products not subject to Apothecaries's or Tower weight.
|English unit||SI ('Metric')||Relationship|
|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)||28.35g||1oz = 16 dr = 437.5 grains|
|Pound (lb)||453.59237g||1 lb= 16 oz = 7000 grains ('lb' is an abbreviation for the Ancient Roman unit libra)|
|Stone (st)||6.35 kg||1 st = 14 lb (see Stone (unit) for other values)|
|Quarter (qr)||12.7 kg||1 qr = 1⁄4 cwt, or 2 st, or 28 lb|
|Hundredweight (cwt)||50.8 kg||1 cwt = 112 lb, or 8 st|
|Ton||1.016 tonne||1 ton = 20 cwt, or 2240 lb|
|Nail||3.175 kg||1 nail = 1⁄16 cwt = 7 lb|
|Clove||?||7 lb (wool) or 8 lb (cheese)|
|Tod||12.7 kg||1 tod = 2 st = 1⁄4 cwt|
The Troy and Tower pounds and their subdivisions were used for coins and precious metals. The Tower pound, which was based upon an earlier Anglo-Saxon pound, was replaced by the Troy pound when a proclamation dated 1526 required the Troy pound to be used for mint purposes instead of the Tower pound. No standards of the Tower pound are known to have survived.
|Avoirdupois||1||175/144||= 1.21527||35/27||= 1.296||28/27||= 1.037||35/36||= 0.972||≈ 0.9072||16||14+7/12||= 14.583||15+5/9||= 15.5||7000||9955+5/9||≈ 454||≈ 5/11|
|Troy||144/175||≈ 0.8229||1||16/15||= 1.06||64/75||= 0.853||4/5||= 0.8||≈ 0.7465||13+29/175||≈ 13.17||12||12+4/5||= 12.8||5760||8192||≈ 373||≈ 3/8|
|Tower||27/35||≈ 0.7714||15/16||= 0.9375||1||4/5||= 0.8||3/4||= 0.75||≈ 0.6998||12+12/35||≈ 12.34||11+1/4||= 11.25||12||5400||7680||≈ 350||≈ 7/20|
|Merchant||27/28||≈ 0.9643||75/64||= 1.171875||5/4||= 1.25||1||15/16||= 0.9375||≈ 0.8748||15+3/7||≈ 15.43||14+1/16||= 14.0625||15||6750||9600||≈ 437||≈ 7/16|
|London||36/35||≈ 1.029||5/4||= 1.25||4/3||= 1.3||16/15||= 1.06||1||≈ 0.9331||16+16/35||≈ 16.46||15||16||7200||10240||≈ 467||≈ 7/15|
|Metric||≈ 1.1023||≈ 1.3396||≈ 1.4289||≈ 1.1431||≈ 1.0717||1||≈ 17.64||≈ 16.08||≈ 17.15||7716||10974||= 500||= 1/2|
In 1758 the legislature turned attention to this subject; and after some investigations on the comparative lengths of the various standards, ordered a rod to be made of brass, about 38 or 39 inches long, graduated (measured) from the Royal Society's yard: this was marked “Standard Yard, 1758,” and was given into the care of the clerk of the House of Commons. For commercial purposes another bar was made, with the yard marked off from the same standard; but it had two upright fixed markers, placed exactly one yard apart, between which any commercial yard measures might be placed, in order to have their accuracy tested: it was graded in feet, one of the feet was graded in inches, and one of the inches in ten parts. This standard yardstick was kept at the Exchequer. In 1760, a copy of Bird's standard, made two years before, was constructed.
from Richard Boyle, 1616