English units were 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. 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 descendant Imperial system as well to those of the descendant system of United States customary units. 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. In England (and the British Empire), English units were replaced by Imperial units in 1824 (effective as of 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. In the US, being independent from the British Empire decades before the 1824 reforms, English units were standardized and adopted (as "US Customary Units") in 1832.

History

Very little is known of the units of measurement used in 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 rods × 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" 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 square 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. The Norman conquest of England introduced just 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, but does not define these 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 1963). Over time, the English system had spread to other parts of the British Empire.

Timeline

Selected excerpts from the bibliography of Marks and Marking of Weights and Measures of the British Isles

Length

Area

Administrative units

Volume

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.

General liquid measures

Liquid measures as binary submultiples of their respective gallons (ale or wine):

Wine

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.

Ale and beer

Grain and dry goods

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: Other units included the wey (6 or sometimes 5 seams or quarters), and the last (10 seams or quarters).

Specific goods

Chemistry

At that reference, water has a density of ≃ 0.9988g/ml (438.0grain⁄imp fl oz or 1.001ozav⁄imp fl oz), and thus:

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. 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 was eventually standardised as 7,000 grains and was used for all products not subject to Apothecaries's or Tower weight.

Avoirdupois

Troy and Tower

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. Established in the 8th century by Offa of Mercia, a pound sterling (or "pound of sterlings" ) was that weight of sterling silver sufficient to make 240 silver pennies.

Troy

Tower

Apothecary

Others