Historically, in different parts of the world, at different points in time, and for different applications, the pound (or its translation) has referred to broadly similar but not identical standards of mass or force.
Roman The (Latin for 'scale'/'balance') is an
ancient Roman unit of mass that is now equivalent to . It was divided into 12 (singular: ), or ounces. The is the origin of the abbreviation for pound, "lb".
In Britain A number of different definitions of the pound have historically been used in Britain. Among these are the
avoirdupois pound, which is the common pound used for weights, and the obsolete
tower,
merchants' and
London pounds. The
troy pound and ounce remain in use only for the weight of
precious metals, especially in their trade. The weights of traded precious metals, such as gold and silver, are normally quoted just in ounces (e.g. "500 ounces") and, when the type of ounce is not explicitly stated, the
troy system is assumed. The
pound sterling money system, which was introduced during the reign of
King Offa of
Mercia (757–96), was based originally on a Saxon pound of silver. After the
Norman conquest the Saxon pound was known as the tower pound or moneyer's pound. In 1528, during the reign of
Henry VIII, the coinage standard was changed by parliament from the tower pound to the
troy pound.
Avoirdupois pound The avoirdupois pound, also known as the wool pound, first came into general use c. 1300. It was initially equal to 6,992 troy grains. The pound avoirdupois was divided into 16 ounces. During the reign of
Queen Elizabeth I, the avoirdupois pound was redefined as 7,000 troy grains. Since then, the
grain has often been an integral part of the avoirdupois system. By 1758, two Elizabethan Exchequer standard weights for the avoirdupois pound existed, and when measured in troy grains they were found to be of 7,002 grains and 6,999 grains.
Imperial standard pound In the United Kingdom, weights and measures have been defined by a long series of Acts of Parliament, the intention of which has been to regulate the sale of commodities. Materials traded in the marketplace are quantified according to accepted units and standards in order to avoid fraud. The standards themselves are legally defined so as to facilitate the resolution of disputes brought to the courts; only legally defined measures will be recognised by the courts. Quantifying devices used by traders (weights, weighing machines, containers of volumes, measures of length) are subject to official inspection, and penalties apply if they are fraudulent. The
Weights and Measures Act 1878 (
41 & 42 Vict. c. 49) marked a major overhaul of the British system of weights and measures, and the definition of the pound given there remained in force until the 1960s. The pound was defined thus (Section 4): "The ... platinum weight ... deposited in the Standards department of the Board of Trade ... shall continue to be the imperial standard of ... weight ... and the said platinum weight shall continue to be the imperial standard for determining the imperial standard pound for the United Kingdom". Section 13 states that the weight of this standard shall be called the imperial standard pound, and that all other weights mentioned in the act and permissible for commerce shall be ascertained from it alone. The first schedule of the act gave more details of the standard pound: it is a platinum cylinder nearly high, and diameter, and the edges are carefully rounded off. It has a groove about from the top, to allow the cylinder to be lifted using an ivory fork. It was constructed following the destruction of the Houses of Parliament by fire in 1834, and is stamped "P.S. 1844, 1 lb" (P.S. stands for "Parliamentary Standard").
Redefinition in terms of the kilogram The British
Weights and Measures Act 1878 (
41 & 42 Vict. c. 49) said that contracts worded in terms of metric units would be deemed by the courts to be made according to the Imperial units defined in the Act, and a table of metric equivalents was supplied so that the Imperial equivalents could be legally calculated. This defined, in UK law, metric units in terms of Imperial ones. The equivalence for the pound was given as 1 lb = or 0.45359 kg, which made the kilogram equivalent to about . In 1883, it was determined jointly by the standards department of the British Board of Trade and the Bureau International that was a better approximation, and this figure, rounded to was given legal status by an
Order in Council in May 1898. In 1959, based on further measurements and international coordination, the
International Yard and Pound Agreement defined an "international pound" as being equivalent to exactly .) is equal to 12
troy ounces and to 5,760 grains, which is exactly grams. Troy weights were used in England by jewellers. Apothecaries also used the troy pound and ounce, but added the drachms and scruples unit in the
apothecaries' system of weights.
Troy weight may take its name from the French market town of
Troyes in France where English merchants traded at least as early as the early 9th century.
Tower pound of 240 early
silver pennies (original
pennyweight) A tower pound is equal to 12 tower ounces and to 5,400
troy grains, which equals around 350 grams. The tower pound is the historical weight standard that was used for England's coinage. Before the
Norman conquest in 1066, the tower pound was known as the Saxon pound. During the reign of
King Offa (757–796) of
Mercia, a Saxon pound of silver was used to set the original weight of a
pound sterling. In the pound sterling monetary system, twelve pennies equaled a
shilling and twenty shillings equaled a pound sterling. The tower pound was referenced to a standard prototype found in the
Tower of London. The tower system ran concurrently with the avoirdupois and troy systems until the reign of
Henry VIII, when a royal proclamation dated 1526 required that the troy pound be used for mint purposes instead of the tower pound. No standards of the tower pound are known to have survived. The tower pound was also called the '''moneyers' pound
(referring to the Saxon moneyers before the Norman conquest); the easterling pound
, which may refer to traders of eastern Germany, or to traders on the shore of the eastern Baltic sea, or dealers of Asiatic goods who settled at the London Steelyard wharf; and the Rochelle pound''' by French writers, because it was also in use at
La Rochelle. An almost identical weight was employed by the Germans for weighing gold and silver. The mercantile pound (1304) of 6750 troy grains, or 9600 Tower grains, derives from this pound, as 25
shilling-weights or 15 Tower ounces, for general commercial use. Multiple pounds based on the same ounce were quite common. In much of Europe, the apothecaries' and commercial pounds were different numbers of the same ounce.
Merchants' pound The merchants' pound (
mercantile pound, , or
commercial pound) was considered to be composed of 25 rather than 20
Tower shillings of 12
pence. It was equal to 9,600 wheat grains (15 tower ounces or 6,750 grains) and was used in England until the 14th century The difference is so insignificant that it can be ignored for almost all practical purposes.
Byzantine litra The Byzantines used a series of measurements known as pounds (, ). The most common was the (, "pound of account"), established by
Constantine the Great in 309/310. It formed the basis of the Byzantine
monetary system, with one of gold equivalent to 72 . A hundred were known as a (, "hundredweight"). Its weight seems to have decreased gradually from the original to . Due to its association with gold, it was also known as the (, "gold pound") or (, "maritime pound"), but it could also be used as a measure of land, equalling a fortieth of the . The was specifically used for weighing olive oil or wood, and corresponded to 4/5 of the or . Some outlying regions, especially in later times, adopted various local measures, based on Italian, Arab or Turkish measures. The most important of these was the (, "silver pound") of , found in
Trebizond and
Cyprus, and probably of Arab origin. The or is equivalent to about and was used between the 1350s and the late 18th century. The unusually heavy Habsburg (civil) pound of 16 ounces was later defined in terms of .
Bavarian reforms in 1809 and 1811 adopted essentially the same standard as the Austrian pound. In
Prussia, a reform in 1816 defined a uniform civil pound in terms of the Prussian foot and distilled water, resulting in a Prussian pound of . Between 1803 and 1815, all German regions west of the
River Rhine were under French control, organised in the
departements:
Roer,
Sarre,
Rhin-et-Moselle, and
Mont-Tonnerre. As a result of the
Congress of Vienna, these regions again became part of various German states. However, many of these regions retained the metric system and adopted a metric pound of precisely . In 1854, the pound of 500 g also became the official mass standard of the
German Customs Union and was renamed the , but local pounds continued to co-exist with the pound for some time in some German states. Nowadays, the term is sometimes still in use and universally refers to a pound of 500 g.
Russian The Russian pound (, ) is an
obsolete Russian unit of measurement of mass. It is equal to . In 1899, the was the basic unit of weight, and all other units of weight were formed from it; in particular, a was of a , and a was 40 .
The was a Scandinavian measurement that varied in weight between regions. From the 17th century onward, it was equal to in Sweden but was abandoned in 1889 when Sweden switched to the metric system. In Norway, the same name was used for a weight of . In Denmark, it equaled . In the 19th century, Denmark followed Germany's lead and redefined the pound as .
Portuguese and The Portuguese unit that corresponds to the pounds of different nations is the , equivalent to 16 ounces of , a variant of the Cologne standard. This was introduced in 1499 by
Manuel I,
king of Portugal. Based on an evaluation of bronze nesting weight piles distributed by Manuel I to different towns, the of Manuel I has been estimated to be of . In the early 19th century, the was evaluated at . In the 15th century, the was of 14 ounces of or . The Portuguese was the same as 2 . There were also of 12.5 and 13 ounces and of 15 and 16 ounces. The or standard was also used.
Jersey pound A Jersey pound is an obsolete unit of mass used on the island of
Jersey from the 14th century to the 19th century. It was equivalent to about 7,561 grains (). It may have been derived from the
French livre poids de marc.
Trone pound The trone pound is one of a number of
obsolete Scottish units of measurement. It was equivalent to between 21 and 28 avoirdupois ounces (about ).
Metric pound In many countries, upon the introduction of a
metric system, the pound (or its translation) became an historic and obsolete term, although some have kept it as an informal term without a specific value. In
German, the term is , in
French , in Dutch , in
Spanish and
Portuguese , in
Italian , and in
Danish and
Swedish . Though not from the same linguistic origin, the Chinese (, also known as the "
catty") in
mainland China has a modern definition of exactly , divided into 10 (). Traditionally around , the has been in use for more than two thousand years varying in exact value from one period to another, serving the same purpose as "pound" for the common-use measure of weight. In Hong Kong, for the purposes of commerce and trade between Britain and Imperial China in the preceding centuries, three Chinese catties were equivalent to four British imperial pounds, defining one catty as in weight precisely. Hundreds of older pounds were replaced in this way. Examples of the older pounds are one of around in Spain, Portugal, and Latin America; one of in Norway; and several different ones in what is now Germany. From the introduction of the kilogram scales and measuring devices are denominated only in
grams and
kilograms. A pound of product must be determined by weighing the product in grams as the use of the
pound is not sanctioned for trade within the
European Union. == Use in weaponry ==