The pound or pound-mass is a unit of mass
used in the imperial, United States customary and other systems of measurement. A number
of different definitions have been used, the most common today being the international
avoirdupois pound which is legally defined as exactly 0.45359237 kilograms, and which
is divided into 16 avoirdupois ounces. The unit is descended from the Roman libra;
the name pound is a Germanic adaptation of the Latin phrase libra pondo, ‘a pound by
weight’. Usage of the unqualified term pound reflects
the historical conflation of mass and weight. This accounts for the modern distinguishing
terms pound-mass and pound-force. Current use
The United States and countries of the Commonwealth of Nations agreed upon common definitions
for the pound and the yard. Since 1 July 1959, the international avoirdupois pound has been
defined as exactly 0.45359237 kg. In the United Kingdom, the use of the international
pound was implemented in the Weights and Measures Act 1963. The yard or the metre shall be the unit of
measurement of length and the pound or the kilogram shall be the unit of measurement
of mass by reference to which any measurement involving a measurement of length or mass
shall be made in the United Kingdom; and- the yard shall be 0.9144 metre exactly; the
pound shall be 0.45359237 kilogram exactly. An avoirdupois pound is equal to 16 avoirdupois
ounces and to exactly 7,000 grains. The conversion factor between the kilogram and the international
pound was therefore chosen to be divisible by 7, and an grain is thus equal to exactly
64.79891 milligrams. Historic use Historically, in different parts of the world,
at different points in time, and for different applications, the pound has referred to broadly
similar but not identical standards of mass or force.
Roman libra The libra is an ancient Roman unit of mass
that was equivalent to approximately 328.9 grams. It was divided into 12 uncia, or ounces.
The libra is the origin of the abbreviation for pound, lb. The commonly used abbreviation
lbs to indicate the plural unit of measurement does not reflect Latin usage, in which lb
is both the singular and plural abbreviation. In Britain
A number of different definitions of the pound have been used in Britain. Amongst these are
the avoirdupois pound and the obsolete tower, merchant’s and London pounds. The weight of
precious metals when given in pounds and/or ounces usually assumes Troy pounds and ounces;
these units are not otherwise used today. Historically the pound sterling was a tower
pound of silver. In 1528 the standard was changed 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 6992 troy grains. The pound avoirdupois was divided into 16
ounces. During the reign of Queen Elizabeth, 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 are subject to official inspection, and penalties apply if they are fraudulent.
The Weights and Measures Act of 1878 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 ‘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’. Paragraph 13 states that the weight
‘in vacuo’ 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 1.35 inches high, and 1.15 inches diameter, and the edges are
carefully rounded off. It has a groove about 0.34 inches 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. This definition of the Imperial
pound remains unchanged. Relationship to the kilogram
The 1878 Act 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. Thus
defining, in UK law, metric units in terms of Imperial ones. The equivalence for the
pound is given as 1 lb=453.59265 g or 0.45359 kg, which would make the kilogram
weigh approximately 2.2046213 lb. In 1883, it was determined jointly by the Standards
Department of the Board of Trade and the Bureau International that 0.4535924277 kg was a
better approximation, and this figure, rounded to 0.45359243 kg was given legal status by
an Order in Council in May 1898. However in 1963 a new Weights and Measures
Act reversed this relationship and the pound was defined for the first time as a mass equal
to 0.45359237 kg to match the definition of the international pound agreed in 1959.
Troy pound A troy pound is equal to 12 troy ounces and
to 5,760 grains, that is exactly 373.2417216 grams. Troy weights were used in England by
apothecaries and jewellers. Troy weight probably takes its name from the
French market town of Troyes in France where English merchants traded at least as early
as the early 9th century. The troy pound is no longer in general use
or legal unit for trade. In the United Kingdom, the use of the troy pound was abolished on
6 January 1879 by the WMA Weights and Measures Act of 1878, though the troy ounce was retained.
The troy ounce is still used for measurements of precious metals such as gold, silver, and
platinum, and sometimes gems such as opals. Most measurements of the mass of precious
metals using pounds refer to troy pounds, even though it is not always explicitly stated
that this is the case. Some notable exceptions are:
Encyclopædia Britannica which uses either avoirdupois pounds or troy ounces, likely
never both in the same article, and the mass of Tutankhamun’s sarcophagus lid.
This is 110 kilograms. It is often stated to have been 242 or 243 avoirdupois pounds
but sometimes, much less commonly, it is stated as 296 pounds.
Tower pound The system called tower weight was the more
general name for King Offa’s pound. This dates to 757 AD and was based on the silver penny.
This in turn was struck over Arabic dirhams. The pound was based on the weight of 120 Arabic
silver dirhams, which have been found in Offa’s Dyke. The same coin weight was used throughout
the Hanseatic League. The mercantile pound 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. The tower system was referenced to a standard
prototype found in the Tower of London and ran concurrently with the avoirdupois and
troy systems, until the reign of Henry VIII when a royal 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. The tower pound is equivalent to about 350
grams. Merchants’ pound
The merchants’ pound was equal to 9,600 wheat grains and was used in England until the 14th
century for most goods. London pound
The London pound is that of the Hansa, as used in their various trading places. This
is based on 16 tower ounces, each ounce divided as the tower ounce. It never became a legal
standard in England; the use of this pound waxed and waned with the influence of the
Hansa itself. A London pound was equal to 7,200 troy grains.
In the United States In the United States, the avoirdupois pound
as a unit of mass has been officially defined in terms of the kilogram since the Mendenhall
Order of 1893. That Order defined the pound to be 2.20462 pounds to a kilogram. The following
year this relationship was refined as 2.20462234 pounds to a kilogram, following a determination
of the British pound. According to a 1959 NIST publication, the
United States 1894 pound differed from the international pound by approximately one part
in 10 million. 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 pound. The most common was the logarikē
litra, established by Constantine the Great in 309/310. It formed the basis of the Byzantine
monetary system, with one litra of gold equivalent to 72 solidi. A hundred litrai were known
as a kentēnarion. Its weight seems to have decreased gradually from the original 324
grams to 319. Due to its association with gold, it was also known as the chrysaphikē
litra or thalassia litra, but it could also be used as a measure of land, equalling a
fortieth of the thalassios modios. The soualia litra was specifically used for
weighing olive oil or wood, and corresponded to 4/5 of the logarikē, i.e. 256 g. 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 argyrikē litra of 333 g,
found in Trebizond and Cyprus, and probably of Arab origin.
French livre Since the Middle Ages, various pounds have
been used in France. Since the 19th century, a livre has referred to the metric pound,
500g. The livre esterlin was equivalent to about
367.1 grams and was used between the late 9th century and the mid-14th century.
The livre poids de marc or livre de Paris was equivalent to about 489.5 grams and was
used between the 1350s and the late 18th century. It was introduced by the government of John
II. The livre métrique was set equal to the kilogram
by the decree of 13 Brumaire an IX between 1800 and 1812. This was a form of official
metric pound. The livre usuelle was defined as 500 grams,
by the decree of 28 March 1812. It was abolished as a unit of mass effective 1 January 1840
by a decree of 4 July 1837, but is still used informally.
German and Austrian Pfund Originally derived from the Roman libra, the
definition varied throughout Germany in the Middle Ages and onward. The measures and weights
of the Habsburg monarchy were reformed in 1761 by Empress Maria Theresia of Austria.
The unusually heavy Habsburg pound of 16 ounces was later defined in terms of 560.012 grams.
Bavarian reforms in 1809 and 1811 adopted essentially the same standard 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 467.711 grams.
Between 1803 and 1815 all German regions west of the River Rhine were French, organised
in the departements: Roer, Sarre, Rhin-et-Moselle, and Mont-Tonnerre. As a result of the Congress
of Vienna these became part of various German states. However, many of these regions retained
the metric system and adopted a metric pound of precisely 500 grams. In 1854 the pound
of 500 grams also became the official mass standard of the German Customs Union, but
local pounds continued to co-exist with the Zollverein pound for some time in some German
states. Nowadays, the term Pfund is still in common use and universally refers to a
pound of 500 grams. Russian funt
The Russian pound is an obsolete Russian unit of measurement of mass. It is equal to 409.51718
grams. In 1899 the Russian pound was the basic unit of weight and all other units of weight
were formed from it. Skålpund
The Skålpund was a Scandinavian measurement that varied in weight between regions. From
the 17th century onward, it was equal to 425.076 grams 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 498.1 grams. In Denmark it equalled 471 grams.
In the 19th century Denmark followed Germany’s lead and redefined the pound as 500 grams.
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.
Metric pounds In many countries upon the introduction of
a metric system, the pound became an informal term for 500 grams,
The Dutch pond is an exception. It was officially redefined as 1 kilogram,
with an ounce of 100 grams, but people seldom use it this way. In daily life pond is exclusively
used for amounts of 500 grams, and to a lesser extent, ons for 100 grams.
In German the term is Pfund, in French livre, in Dutch pond, in Spanish and Portuguese libra,
in Italian libbra, and in Danish and Swedish pund.
Though not from the same linguistic origin, the Chinese jīn has a modern definition of
exactly 500 grams, divided into 10 liǎng. Traditionally about 605 grams, the jin has
been in use for more than two thousand years, serving the same purpose as “pound” for the
common-use measure of weight. Hundreds of older pounds were replaced in
this way. Examples of the older pounds are one of around 459 to 460 grams in Spain, Portugal,
and Latin America; one of 498.1 grams in Norway; and several different ones in what is now
Germany. Although the use of the pound as an informal
term persists in these countries to a varying degree, 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 Smoothbore cannon and carronades are designated
by the weight in imperial pounds of round solid iron shot of diameter to fit the barrel.
A cannon that fires a six-pound ball, for example, is called a six-pounder. Standard
sizes are 6, 12, 18, 24, 32 and 42 pounds; 68-pounders also exist, and other nonstandard
weapons use the same scheme. See carronade. A similar definition, using lead balls, exists
for determining the gauge of shotguns. Notes External links
Conversion between units Yahoo Conversion Calculator.
U.S. National Institute of Standards and Technology Special Publication 811
National Institute of Standards and Technology Handbook 130