View source for Pound (mass)

{{Short description|Unit of mass}}
{{other uses|Pound (disambiguation)}}
{{Redirect2|lb.|lbs.|other uses|LB (disambiguation){{!}}LB|and|LBS (disambiguation){{!}}LBS}}
{{Use dmy dates|date=March 2020}}
{{Infobox unit
| bgcolor      = 
|image=File:One pound avoirdupois weight - Musée des arts et métiers - Inv 3287 - 01.jpg
|caption=One-pound avoirdupois weight, from the [[Musée des Arts et Métiers]]
| name         = pound
| standard     = {{ubl|[[imperial units|British imperial units]],|[[United States customary units]]}}
| quantity     = mass
| symbol       = lb
| units1       = [[International System of Units|SI units]]
| inunits1     = {{val|0.45359237|u=kg}}
| units2       = [[Avoirdupois system|Avoirdupois]]
| inunits2     = 16 [[Ounce#International avoirdupois ounce|ounces]]
}}

The '''pound''' or '''pound-mass''' is a [[Units of measurement|unit]] of [[mass]] used in both the [[imperial units|British imperial]] and [[United States customary units|United States customary]] [[systems of measurement]]. Various definitions have been used; the most common today is the international [[avoirdupois]] pound, [[International yard and pound|which is legally defined]] as exactly {{val|0.45359237|ul=kilograms}}, and which is divided into 16 avoirdupois [[ounces]].<ref name=NGS/> The international standard symbol for the avoirdupois pound is '''lb''';<ref>IEEE Std 260.1-2004, IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units)</ref> an alternative symbol (when there might otherwise be a risk of confusion with the [[pound-force]]) is '''lb<sub>m</sub>'''<ref name="isbn_978-0135018583">{{Citation |last1=Fletcher |first1=Leroy S. |last2=Shoup |first2=Terry E. |year=1978 |title=Introduction to Engineering |publisher=Prentice-Hall |url=https://books.google.com/books?id=tyohAQAAIAAJ |isbn=978-0135018583 |lccn=77024142 |postscript=.}}{{rp|257}}</ref> (for most pound definitions), '''#''' ([[number sign|chiefly in the U.S.]]),<ref>{{Cite web |url=https://en.oxforddictionaries.com/definition/pound_sign |archive-url=https://web.archive.org/web/20180403051651/https://en.oxforddictionaries.com/definition/pound_sign |url-status=dead |archive-date=3 April 2018 |title=pound sign |website=[[Oxford English Dictionary]]}}</ref> and '''{{not a typo|℔}}'''<ref>{{cite book|title=The Unicode Standard, Version 15.0 |chapter=Letterlike Symbols {{!}} Range: 2100–214F |chapter-url=http://unicode.org/charts/PDF/U2100.pdf  |quote= {{not a typo|{{nobr|2114  ℔  {{resize|L B BAR SYMBOL}}}}}} |publisher=[[Unicode Consortium]] |access-date=28 April 2011 |page=2100/2123}}</ref> or '''{{pprime}}̶'''<ref>{{cite web|title=The Dictionary of Medical and Surgical Knowledge|year = 1864|url=https://books.google.com/books?id=SIVZAAAAcAAJ&pg=PA62|access-date=22 September 2016}}</ref> (specifically for the [[apothecaries' system|apothecaries' pound]]).

The unit is descended from the [[Ancient Roman units of measurement#Weight|Roman {{lang|la|libra|nocat=y}}]] (hence the symbol ''lb'', descended from the [[scribal abbreviation]], ''{{not a typo|℔}}'').  The English word ''pound'' comes from the Roman {{lang|la|libra pondo}} ('the weight measured in {{lang|la|[[#libra|libra]]}}'), and is [[cognate]] with, among others, [[German language|German]] {{lang|de|Pfund}}, [[Dutch language|Dutch]] {{lang|nl|pond}}, and [[Swedish language|Swedish]] {{lang|sv|pund}}. These units are now designated as historical and are no longer in common usage, being replaced by the [[metric system]].

Usage of the unqualified term ''pound'' reflects the [[mass versus weight|historical conflation of mass and weight]]. This accounts for the modern distinguishing terms ''pound-mass'' and ''[[pound-force]]''.

== Etymology ==
The word 'pound' and its cognates ultimately derive from a borrowing into [[Proto-Germanic language|Proto-Germanic]] of the Latin expression {{lang|la|libra pondo}} ('the weight measured in {{lang|la|[[#libra|libra]]}}'), in which the word {{lang|la|pondo}} is the [[ablative case|ablative]] singular of the Latin noun {{lang|la|pondus}} ('weight').<ref>''Oxford English Dictionary'', ''s.v.'' 'pound'</ref>

== Current use <span class="anchor" id="international pound"></span> ==
The United States and the [[Commonwealth of Nations]] agreed upon common definitions for the pound and the [[yard]]. Since 1 July 1959, the [[International yard and pound|international avoirdupois pound]] (symbol lb) has been defined as exactly {{val|0.45359237|u=kg}}.<ref name="Standards1959">{{cite book|location=United States |title=Research Highlights of the National Bureau of Standards|url=https://books.google.com/books?id=4aWN-VRV1AoC&pg=PA13|access-date=12 July 2012|year=1959|publisher=Department of Commerce, [[National Institute of Standards and Technology|National Bureau of Standards]]|page=13}}</ref><ref>Multiple sources:
*[http://physics.nist.gov/Pubs/SP447/app8.pdf "Appendix 8"].{{vague|reason=appendix 8 of what?|date=August 2025}} National Bureau of Standards. {{webarchive|url=https://web.archive.org/web/20090118111241/http://www.physics.nist.gov/Pubs/SP447/app8.pdf |date=18 January 2009 }}
* Bigg, P. H., et al. [http://www.iop.org/EJ/abstract/0508-3443/13/9/305 "Re-determination of the values of the imperial standard pound and of its parliamentary copies in terms of the international kilogramme during the years 1960 and 1961"]. National Physical Laboratory.
* [http://www.sizes.com/units/pound_avoirdupois.htm "pound avoirdupois"]. ''Sizes.com''. {{Webarchive|url=https://web.archive.org/web/20191024120334/http://www.sizes.com/units/pound_avoirdupois.htm |date=24 October 2019 }}.</ref>

In the United Kingdom, the use of the international pound was implemented in the [[Weights and Measures Act 1963]].<ref>Quoted by [[John Laws (judge)|Lord Justice Laws]] in the "[[Metric Martyrs]]" case: {{cite BAILII |court=EWHC |division=Admin |year=2002 |num=195 |litigants=Thoburn v Sunderland City Council, Hunt v London Borough of Hackney, Harman & Dove v Cornwall County Council, Collins v London Borough of Sutton |access-date=12 August 2006}}</ref>

{{Blockquote|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— {{ubli|style=margin-left: 1.4em; font-size: initial
|(a) the yard shall be 0.9144 metre exactly;
|(b) the pound shall be {{gaps|0.453|592|37}} kilogram exactly.}}|Weights and Measures Act 1963, Section 1(1)<ref name="vlex 1963">{{cite legislation UK |type=act |year=1963 |chapter=31 <!--This Act is only available as PDF, section links are 404: |section=1--> |act=Weights and Measures Act 1963}}</ref>}}

An [[avoirdupois]] pound is equal to 16 avoirdupois [[ounce]]s and to exactly 7,000 [[Grain (unit)|grain]]s. The conversion factor between the kilogram and the international pound was therefore chosen to be divisible by 7 with a [[terminating decimal]] representation, and an (international) grain is thus equal to exactly {{val|64.79891|ul=milligrams}}.

In the United Kingdom, the process of [[metrication in the United Kingdom|metrication]] and [[European units of measurement directives]] were expected to eliminate the use of the pound and ounce, but in 2007 the European Commission abandoned the requirement for metric-only labelling on packaged goods there, and allowed for dual [[metric system|metric]]–[[imperial units|imperial]] marking to continue indefinitely.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/uk/6988521.stm |title=EU gives up on 'metric Britain' |work=BBC News |access-date=4 May 2015 |date=11 September 2007}}</ref><ref>{{cite news|title=Will British people ever think in metric?|url=https://www.bbc.co.uk/news/magazine-16245391|work=BBC News|access-date=4 May 2015|date=21 December 2011|first1=Jon|last1=Kelly}}</ref>

In the United States, the [[Metric Conversion Act|Metric Conversion Act of 1975]] declared the metric system to be the "preferred system of weights and measures" but did not suspend use of [[United States customary units]], and the United States is the only industrialised country where commercial activities do not predominantly use the metric system,<ref name="World Factbook">
{{cite book
  | url        = https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html
  | archive-url = https://web.archive.org/web/20070613023743/https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html
  | url-status = dead
  | archive-date = 13 June 2007
  | title      = The World Factbook
  | date       = 17 January 2007
  | publisher  = [[Central Intelligence Agency]]
  | chapter    = Appendix G – Weights and Measures
  | access-date = 4 February 2007
}}</ref> despite [[metrication in the United States|many efforts to do so]], and the pound remains widely used as one of the key customary units.<ref>{{cite web | title=US 1988 law on metrification |url=https://www.law.cornell.edu/cfr/text/48/611.002-70 |access-date=21 September 2019}}</ref><ref>{{cite web|title=Countries not using SI |date=22 March 2011 |url=https://www.zmescience.com/other/map-of-countries-officially-not-using-the-metric-system/ |access-date=21 September 2019 }}</ref>

== Historical use ==
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.{{efn|The pound is often described as a unit of "weight", and the word "weight" can refer to either mass or force depending on context. Historically and in common parlance, "weight" refers to mass, but [[weight]] as used in modern physics is a force.}}
{{Wide image|comparison of pounds.svg|950|Comparison of the relative sizes of avoirdupois, troy, Tower, merchant and London pounds}}
{{Tall image|Gewichtmaße1.jpg|250|500|Various historic pounds from a German textbook dated 1848}}
=== Roman {{lang|la|libra}}<span class="anchor" id="libra"></span> ===

The {{lang|la|libra}} (Latin for 'scale'/'balance') is an [[Ancient Roman units of measurement|ancient Roman unit]] of mass that is now equivalent to {{convert|328.9|g|oz|abbr=on}}.<ref name="Zupko1977">{{cite book |last=Zupko |first=Ronald Edward |author-link=Ronald Edward Zupko |title=British weights & measures: a history from antiquity to the seventeenth century |url=https://books.google.com/books?id=pWUgAQAAIAAJ&q=5076 |access-date=27 November 2011 |year=1977 |publisher=Univ. of Wisconsin Press |page=7|isbn=9780299073404 }}</ref><ref name="Skinner1967">{{cite book |author=Frederick George Skinner |title=Weights and measures: their ancient origins and their development in Great Britain up to A.D. 1855 |url=https://books.google.com/books?id=bDcLAQAAIAAJ&q=roman+libra+328 |access-date=27 November 2011 |year=1967 |publisher=H.M.S.O. |page=65|isbn=9789140059550 }}</ref><ref name="Chambers's encyclopaedia">{{cite book |title=Chambers's encyclopaedia |url=https://books.google.com/books?id=Z2fQAAAAMAAJ&q=roman+libra+328 |access-date=27 November 2011 |volume=14 |year=1967 |publisher=Pergamon Press |page=476}}</ref> It was divided into 12 {{lang|la|unciae}} (singular: {{lang|la|uncia}}), or ounces. The {{lang|la|libra}} is the origin of the abbreviation for pound, "lb".

=== In Britain ===
{{See also|English units of measurement}}

A number of different definitions of the pound have historically been used in Britain. Among these are the [[#Avoirdupois pound|avoirdupois pound]], which is the common pound used for weights, and the obsolete [[#Tower pound|tower]], [[#Merchants' pound|merchants']] and [[#London pound|London]] pounds.<ref>{{cite web| url = http://home.clara.net/brianp/weights.html| title = Grains and drams, ounces and pounds, stones and tons. Personal notes.}}</ref> The [[Troy weight|troy pound and ounce]] remain in use only for the weight of [[precious metal]]s, 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|Norman conquest]] the Saxon pound was known as the tower pound or moneyer's pound.<ref name="Zupko 1977 11">{{Cite book |last=Zupko |first=Ronald Edward |url=http://archive.org/details/britishweightsme0000zupk |title=British weights & measures : a history from antiquity to the seventeenth century |date=1977 |publisher=Madison : University of Wisconsin Press |others=Internet Archive |isbn=978-0-299-07340-4 |pages=11}}</ref> In 1528, during the reign of [[Henry VIII]], the coinage standard was changed by parliament from the tower pound to the [[#Troy pound|troy pound]].<ref>{{Cite book |last=Zupko |first=Ronald Edward |url=http://archive.org/details/britishweightsme0000zupk |title=British weights & measures : a history from antiquity to the seventeenth century |date=1977 |publisher=Madison : University of Wisconsin Press |others=Internet Archive |isbn=978-0-299-07340-4 |pages=78}}</ref>

==== Avoirdupois pound ====
{{broader|Avoirdupois system}}
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 [[Elizabeth I|Queen Elizabeth I]], the avoirdupois pound was redefined as 7,000 troy grains. Since then, the [[Grain (measure)|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.<ref>{{cite journal| last=Skinner | first=F.G. | journal=Bulletin of the British Society for the History of Science | title=The English Yard and Pound Weight | year=1952 | doi=10.1017/S0950563600000646 | volume=1 | pages=184–6| issue=7 }}</ref><ref name="Standards">{{cite book|author=United States. National Bureau of Standards|author-link=National Institute of Standards and Technology|title=weights and measures|url=https://books.google.com/books?id=ycgOAAAAQAAJ&pg=PA22|access-date=26 December 2011|year=1962|publisher=Taylor & Francis|pages=22–24|id=GGKEY:4KXNZ63BNUF}}</ref>{{efn|A difference of just 194.39673 milligrams}}

===== Imperial standard pound<!--Do not capitalise this. It is not a proper noun and is not capitalised in the 1878 Act--> =====
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 {{lang|la|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 {{convert|1.35|in|mm}} high, and {{convert|1.15|in|mm}} diameter, and the edges are carefully rounded off. It has a groove about {{convert|0.34|in|mm}} 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&nbsp;lb" (P.S. stands for "Parliamentary Standard").

{{English pounds}}

===== 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&nbsp;lb = {{val|453.59265|u=g}} or 0.45359&nbsp;kg, which made the kilogram equivalent to about {{val|2.2046213|u=lb}}.

In 1883, it was determined jointly by the standards department of the British Board of Trade and the Bureau International that {{val|0.4535924277|u=kg}} was a better approximation, and this figure, rounded to {{val|0.45359243|u=kg}} was given legal status by an [[Order in Council]] in May 1898.<ref name=nbs447>{{cite book | title=Weights and measures standards of the United States&nbsp;– A brief history | year=1976 | url=http://physics.nist.gov/Pubs/SP447/contents.html | first=L.E. | last=Barbrow | author2=Judson, L.V. | url-status=dead | archive-url=https://web.archive.org/web/20080511153143/http://physics.nist.gov/Pubs/SP447/contents.html | archive-date=11 May 2008 | df=dmy-all }}</ref>

In 1959, based on further measurements and international coordination, the [[International Yard and Pound Agreement]] defined an "international pound" as being equivalent to exactly {{val|0.45359237|u=kg}}.<ref name=nbs447/> This meant that the existing legal definition of the UK pound differed from the international standard pound by {{val|0.06|u=milligrams}}. To remedy this, the pound was again redefined in the United Kingdom by the [[Weights and Measures Act 1963]] to match the international pound, stating: "the pound shall be 0.453 592 37 kilogramme exactly",<ref name="vlex 1963" /> a definition which remains valid to the present day.

The [[2019 revision of the SI]] means that the pound is now defined precisely in terms of fundamental constants, ending the era of its definition in terms of physical prototypes.

==== Troy pound ====
{{main|Troy weight}}

A troy pound (abbreviated lb t<ref>Capotosto, R. (1983). 200 Original Shop Aids and Jigs for Woodworkers. Sterling Publishing Company, Inc.</ref>) is equal to 12 [[troy ounce]]s and to 5,760 grains, that is exactly {{val|373.2417216}} grams.<ref>{{cite web| url=https://www.nist.gov/pml/wmd/pubs/upload/AppC-12-hb44-final.pdf| author=United States National Bureau of Standards | title=Appendix C of NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, General Tables of Units of Measurement| page=C-14}}</ref><!--Source uses U+002D Hyphen-Minus in page number and it should not be changed to n-dash. --> 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.<ref name="zupko" /> The troy pound is no longer in general use or a legal unit for trade (it was abolished in the United Kingdom on 6 January 1879 by the [[Weights and Measures Act 1878]]), but the troy ounce, {{frac|1|12}} of a troy pound, is still used for measurements of gems such as opals, and precious metals such as silver, platinum and particularly gold.<ref>[https://www.fiscal.treasury.gov/fsreports/rpt/goldRpt/current_report.htm "Status Report of U.S. Government Gold Reserve"] {{Webarchive|url=https://web.archive.org/web/20151003044818/https://www.fiscal.treasury.gov/fsreports/rpt/goldRpt/current_report.htm |date=3 October 2015 }}, Bureau of the Fiscal Service</ref>

==== Tower pound ====
[[File:The Pound.jpg|thumb|The tower pound displayed as the weight of a [[pound sterling]] of 240 early [[Penny (English coin)|silver pennies]] (original [[pennyweight]])]]
A tower pound is equal to 12 tower ounces and to 5,400 [[troy grains]], which equals around 350 grams.<ref>{{Cite book |last=Ross |first=Lester A. |url=https://sha.org/assets/documents/Metrology.pdf |title=Archaeological Metrology: English, French, American, and Canadian Systems of Weights and Measures for North American Historical Archaeology |date=1983 |publisher=National Historic Parks and Sites Branch, Parks Canada, Environment Canada |isbn=978-0-660-11336-4 |pages=20 |language=en}}</ref> The tower pound is the historical weight standard that was used for England's coinage.<ref>{{Cite book |last=Kampmann |first=Ursula |url=https://books.google.com/books?id=uVDIEAAAQBAJ&pg=PA56 |title=Drachm, Dirham, Thaler, Pound: Money and currencies in history from earliest times to the euro |date=2013-04-29 |publisher=Conzett |isbn=978-3-03760-029-0 |pages=56 |language=en}}</ref> Before the [[Norman Conquest|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]].<ref name="Zupko 1977 11"/> From one Saxon pound of silver (that is a tower pound) the king had 240 [[Penny (English coin)|silver pennies]] minted.<ref>{{Cite encyclopedia |url=https://books.google.com/books?id=ctLECjLTakcC&pg=PA115 |title=Pound |encyclopedia=Encyclopædia Britannica |edition=11th |volume=21: Payn–Polka |date=1911 |editor-first=Hugh |editor-last=Chisholm |publisher=Cambridge University Press |pages=115 |language=en}}</ref>{{efn|"Anglo-Saxon [[Offa of Mercia|King Offa]] is credited with introducing the system of money to central and southern England in the latter half of the eighth century, overseeing the minting of the earliest English silver pennies{{snd}}emblazoned with his name. In practice they varied considerably in weight and 240 of them seldom added up to a pound. There were at that time no larger denomination coins{{snd}} pounds and [[shilling]]s were merely useful units of account".<ref>{{cite web |title=A short history of the pound |publisher=BBC |first=Ed |last=Lowther |date=14 February 2014 |work=BBC News |url=https://www.bbc.co.uk/news/uk-politics-26169070 |quote= |access-date=22 July 2021 |archive-date=21 July 2021 |archive-url=https://web.archive.org/web/20210721233848/https://www.bbc.co.uk/news/uk-politics-26169070 |url-status=live }}</ref>{{snd}} Ed Lowther, BBC}} In the pound sterling monetary system, twelve pennies equaled a [[shilling]] and twenty shillings equaled a pound sterling.<ref>{{Cite book |last=Geva |first=Benjamin |url=https://books.google.com/books?id=4yHcBAAAQBAJ&pg=PA88 |title=The Payment Order of Antiquity and the Middle Ages: A Legal History |date=2011-11-01 |publisher=Bloomsbury |isbn=978-1-84731-843-5 |pages=88 |language=en}}</ref>

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.<ref>[http://www.sizes.com/units/pound_tower.htm "A proclamation of Henry VIII"]. 5 November 1526. Proclamation 112 in Paul L. Hughes and James F. Larkin, editors. ''Tudor Royal Proclamations''. Volume 1. New Haven: Yale University Press,1964. {{Webarchive|url=https://web.archive.org/web/20140222154017/http://www.sizes.com/units/pound_tower.htm|date=22 February 2014}}</ref> No standards of the tower pound are known to have survived.<ref>R. D. Connor and A. D. C. Simpson. [http://www.sizes.com/units/pound_tower.htm ''Weights and Measures in Scotland. A European Perspective'']. National Museums of Scotland and Tuckwell Press, 2004, page 116, quoting from H. W. Chisholm, Seventh Annual Report of the Warden for the Standards&nbsp;... for 1872–73 (London, 1873), quoting from 1864 House of Commons Paper. {{Webarchive|url=https://web.archive.org/web/20140222154017/http://www.sizes.com/units/pound_tower.htm|date=22 February 2014}}</ref>

The tower pound was also called the '''moneyers' pound''' (referring to the Saxon [[moneyer]]s before the Norman conquest);<ref>{{cite web |title=Tower pound |url=https://sizes.com/units/pound_tower.htm |access-date=17 September 2016 |website=Sizes.com}}</ref> the '''easterling pound''', which may refer to traders of eastern Germany, or to traders on the shore of the eastern [[Baltic Sea|Baltic sea]], or dealers of Asiatic goods who settled at the [[Steelyard|London Steelyard wharf]];<ref>{{cite book |url=https://books.google.com/books?id=uQI_AQAAMAAJ&pg=PP33 |title=Facsimile of First Volume of Ms. Archives of the Worshipful Company of Grocers of the City of London A.D. 1345–1463 |date=1886}}</ref> and the '''Rochelle pound''' by French writers, because it was also in use at [[La Rochelle]].<ref>{{cite book |url=https://books.google.com/books?id=2oUBAAAAQAAJ&pg=PA191 |title=The English manual of banking |year=1877 |access-date=17 September 2016}}</ref> 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.{{Citation needed|date=February 2013}}<ref>{{cite web |title=Weights used for gold |url=http://www.taxfreegold.co.uk/weights.html |access-date=14 January 2011 |publisher=Tax Free Gold}}</ref><ref>{{cite web |title=A brief history of the pound |url=http://www.dozenalsociety.org.uk/history/poundhist.html |access-date=14 January 2011 |publisher=The Dozenal Society of Great Britain}}</ref>
{|
|-
|1 mercantile pound (15&nbsp;oz)
|= 
|align=right|9,600 Tower grains
|= 
|align=right|6,750 troy grains
|-
|1 Tower pound (12&nbsp;oz)
|= 
|align=right|7,680 Tower grains
|= 
|align=right|5,400 troy grains
|-
|1 Tower ounce (20 dwt)
|=
|align=right|640 Tower grains
|=
|align=right|450 troy grains
|-
|1 Tower pennyweight (dwt)
|=
|align=right|32 Tower grains
|=
|align=right|{{frac|22|1|2}} troy grains
|}

==== Merchants' pound ====
The merchants' pound (''mercantile pound'', {{lang|la|libra mercantoria}}, or ''commercial pound'') was considered to be composed of 25 rather than 20 [[Tower pound|Tower shillings]] of 12 [[pennyweight|pence]].<ref name=tract>{{Citation |editor-last=Ruffhead |editor-first=Owen |editor-link=Owen Ruffhead |title=The Statutes at Large |url=https://books.google.com/books?id=tKZFAAAAcAAJ |volume=&nbsp;I: From Magna Charta<!--sic--> to the End of the Reign of King Henry the Sixth. To which is prefixed, A Table of the Titles of all the Publick and Private Statutes during that Time |location=London |publisher=Mark Basket for the Crown |date=1763a |pages=[https://books.google.com/books?id=tKZFAAAAcAAJ&pg=PA148 148–149] }}. {{in lang|en}}&nbsp;& {{in lang|la}}&nbsp;& {{in lang|nrf}}</ref> It was equal to 9,600 wheat grains (15 tower ounces or 6,750 grains)<ref name="zupko">{{cite book|last=Zupko|first=Ronald Edward|author-link=Ronald Edward Zupko|title=Dictionary of Weights and Measures for the British Isles: The Middle Ages to the 20th Century|publisher=DIANE Publishing|isbn=0-87169-168-X|date=1 December 1985}}</ref> and was used in England until the 14th century<ref name="zupko"/> for goods other than [[#Tower pound|money]] and [[#Apothecary's pound|medicine]] ("[[electuaries]]").<ref name=tract/>

==== London pound ====
{{disputed section|London pound|date=January 2021}}
The London pound is that of the [[Hanseatic League|Hansa]], as used in their various trading places.  The London pound is based on 16 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 (16 troy ounces) or, equivalently, 10,240 tower grains (16 tower ounces).

{|
|-
|1 London pound (16&nbsp;oz)
|= 
|align=right|{{frac|1|1|3}} tower pounds (1.25 Troy pounds)
|= 
|align=right|10,240 tower grains
|= 
|align=right|7,200 troy grains
|-
|1 London ounce (20 dwt)
|=
|align=right|1 tower (or troy) ounce
|=
|align=right|640 tower grains
|=
|align=right|450 troy grains
|-
|1 London pennyweight
|=
|align=right|1 tower (or troy) pennyweight
|=
|align=right|32 tower grains
|=
|align=right|{{frac|22|1|2}} 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|Mendenhall Order of 1893]]. That order defined the pound to be {{val|2.20462}} pounds to a kilogram. The following year, this relationship was refined as {{val|2.20462234}} pounds to a kilogram, following a determination of the British pound.<ref name=nbs447 />

In 1959, the United States National Bureau of Standards redefined the pound (avoirdupois) to be exactly equal to 0.453&nbsp;592&nbsp;37&nbsp;kilograms, as had been declared by the [[International Yard and Pound Agreement]] of that year. According to a 1959 [[National Institute of Standards and Technology|NIST]] publication, the United States 1894 pound differed from the international pound by approximately one part in 10 million.<ref name=NGS>{{cite web|url=http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf|author=United States National Bureau of Standards|title=Notices "Refinement of values for the yard and the pound"|date=25 June 1959|access-date=12 August 2006}}</ref> The difference is so insignificant that it can be ignored for almost all practical purposes.<ref>{{cite web|url=http://ts.nist.gov/WeightsAndMeasures/Publications/upload/h4402_appenc.pdf |author=United States National Bureau of Standards |title=Appendix C of NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, General Tables of Units of Measurement |url-status=dead |archive-url=https://web.archive.org/web/20061126120208/http://ts.nist.gov/WeightsAndMeasures/Publications/upload/h4402_appenc.pdf |archive-date=26 November 2006 }} "In Great Britain, the Yard, the Avoirdupois Pound, the troy pound, and the Apothecaries pound are identical with the units of the same names used in the United States." (The introduction to this appendix makes it clear that the appendix is only for convenience and has no normative value: "In most of the other tables, only a limited number of decimal places are given, therefore making the tables better adopted to the average user.")</ref>

==={{anchor|Byzantine litra}} Byzantine litra===
{{main|Byzantine units of measurement#Weight}}

The Byzantines used a series of measurements known as pounds ({{langx|la|libra}}, {{langx|grc|λίτρα|litra}}). The most common was the {{Transliteration|grc|logarikē litra}} ({{lang|grc|λογαρική λίτρα}}, "pound of account"), established by [[Constantine the Great]] in 309/310. It formed the basis of the Byzantine [[Byzantine coinage|monetary system]], with one {{Transliteration|grc|litra}} of gold equivalent to 72 {{Transliteration|grc|[[solidus (coin)|solidi]]}}. A hundred {{Transliteration|grc|litrai}} were known as a {{Transliteration|grc|kentēnarion}} ({{lang|grc|κεντηνάριον}}, "hundredweight"). Its weight seems to have decreased gradually from the original {{convert|324|g|abbr=on}} to {{convert|319|g|abbr=on}}. Due to its association with gold, it was also known as the {{Transliteration|grc|chrysaphikē litra}} ({{lang|grc|χρυσαφική λίτρα}}, "gold pound") or {{Transliteration|grc|thalassia litra}} ({{lang|grc|θαλάσσια λίτρα}}, "maritime pound"), but it could also be used as a measure of land, equalling a fortieth of the {{Transliteration|grc|thalassios [[modios]]}}.<ref name="ODB">{{cite book | title = Oxford Dictionary of Byzantium | chapter = Litra | page = 1238 | last = Schilbach | first = Erich | title-link = Oxford Dictionary of Byzantium | editor-first = Alexander P. | editor-last = Kazhdan | editor-link = Alexander Kazhdan | year = 1991 | publisher = Oxford University Press | isbn = 0-19-504652-8}}</ref>

The {{Transliteration|grc|soualia litra}} was specifically used for weighing olive oil or wood, and corresponded to 4/5 of the {{Transliteration|grc|logarikē}} or {{convert|256|g|abbr=on}}. 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 {{Transliteration|grc|argyrikē litra}} ({{lang|grc|αργυρική λίτρα}}, "silver pound") of {{convert|333|g|abbr=on}}, found in [[Trabzon|Trebizond]] and [[Cyprus]], and probably of Arab origin.<ref name="ODB"/>

=== French livre ===
{{See also|Units of measurement in France before the French Revolution#Mass|Units of measurement in France}}

Since the Middle Ages, various pounds ({{lang|fr|livre}}) have been used in France. Since the 19th century, a {{lang|fr|livre}} has referred to the ''[[#Metric pound|metric pound]]'', 500&nbsp;g.

The {{lang|fr|livre esterlin}} is equivalent to about {{convert|367.1|g|gr}} and was used between the late 9th century and the mid-14th century.<ref name="size.com-Francemass">{{cite web|url=http://www.sizes.com/units/charts/UTBLFrancemass.htm|access-date=12 August 2006|title=Pre-metric French units of mass livre and smaller|date=16 March 2001|author=Sizes, Inc.}}</ref>

The {{lang|fr|livre poids de marc}} or {{lang|fr|livre de Paris}} is equivalent to about {{convert|489.5|g|gr}} and was used between the 1350s and the late 18th century.<ref name="size.com-Francemass" /> It was introduced by the government of [[John II of France|John II]].

The {{lang|fr|livre métrique}} was set equal to the kilogram by the decree of {{lang|fr|13 Brumaire an IX}} between 1800 and 1812. This was a form of official metric pound.<ref name="size.com-Francemass" />

The {{lang|fr|cat=no|livre [[Mesures usuelles|usuelle]]}} (customary unit) was defined as {{convert|500|g|abbr=on}} 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,<ref name="size.com-Francemass" /> but is still used informally.{{citation needed|date=January 2022}}

=== German and Austrian Pfund <span class="anchor" id="Pfund"></span> ===
Originally derived from the Roman libra, the definition varied throughout the [[Holy Roman Empire]] in the Middle Ages and onward. For example, the measures and weights of the [[Habsburg monarchy]] were reformed in 1761 by Empress [[Maria Theresa]] of Austria.<ref name=hille>{{cite journal | last=Hille | first=K.C. | title=Medicinal-Gewicht |page=268 | url=https://books.google.com/books?id=BfI3AAAAMAAJ&pg=RA2-PA268 | journal=Magazin für Pharmacie und die dahin einschlagenden Wissenschaften | year=1831 | location=Heidelberg }}</ref> The unusually heavy Habsburg (civil) pound of 16 ounces was later defined in terms of {{convert|560.012|g|abbr=on}}. [[Bavaria]]n 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 {{convert|467.711|g|abbr=on}}.

Between 1803 and 1815, all German regions west of the [[River Rhine]] were under French control, organised in the [[Departments of France|departement]]s: [[Roer (department)|Roer]], [[Sarre (department)|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 {{convert|500|g|2|abbr=on}}. In 1854, the pound of 500 g also became the official mass standard of the [[Zollverein|German Customs Union]] and was renamed the {{lang|de|cat=no|[[Zollpfund]]}}, but local pounds continued to co-exist with the {{lang|de|Zollverein}} pound for some time in some German states. Nowadays, the term {{lang|de|Pfund}} is sometimes still in use and universally refers to a pound of 500 g.<ref>Entry for [https://www.duden.de/rechtschreibung/Pfund {{lang|de|Pfund}}] {{Webarchive|url=https://web.archive.org/web/20220502163931/https://www.duden.de/rechtschreibung/Pfund |date=2 May 2022 }} at Duden.online.</ref>

=== Russian {{Transliteration|ru|funt}} ===
The Russian pound ({{lang|ru|фунт}}, {{Transliteration|ru|funt}}) is an [[obsolete Russian unit of measurement]] of mass. It is equal to {{convert|409.51718|g|abbr=on}}.<ref>{{cite book |author=Cardarelli, F. |year=2004 |title=Encyclopaedia of Scientific Units, Weights and Measures: Their SI Equivalences and Origins |publisher=Springer |edition=2nd |page=[https://archive.org/details/encyclopaediaofs0000card/page/122 122] |isbn=1-85233-682-X |url=https://archive.org/details/encyclopaediaofs0000card |url-access=registration }}</ref> In 1899, the {{Transliteration|ru|funt}} was the basic unit of weight, and all other units of weight were formed from it; in particular, a {{Transliteration|ru|cat=no|[[zolotnik]]}} was {{frac|96}} of a {{Transliteration|ru|funt}}, and a {{Transliteration|ru|cat=no|[[pood]]}} was 40 {{Transliteration|ru|funty}}.

=== {{lang|sv|Skålpund}} ===
The {{lang|sv|Skålpund}} was a Scandinavian measurement that varied in weight between regions. From the 17th century onward, it was equal to {{convert|425.076|g|abbr=on}} 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 {{convert|425.076|g|abbr=on}}. In Denmark, it equaled {{convert|471|g|abbr=on}}.

In the 19th century, Denmark followed Germany's lead and redefined the pound as {{convert|500|g|abbr=on}}.

=== Portuguese {{lang|pt|libra}} and {{lang|pt|arrátel}} ===
The Portuguese unit that corresponds to the pounds of different nations is the {{lang|pt|arrátel}}, equivalent to 16 ounces of {{lang|pt|Colonha}}, a variant of the Cologne standard. This {{lang|pt|arrátel}} was introduced in 1499 by [[Manuel I of Portugal|Manuel I]], [[Kingdom of Portugal|king of Portugal]]. Based on an evaluation of bronze nesting weight piles distributed by Manuel I to different towns, the {{lang|pt|arrátel}} of Manuel I has been estimated to be of {{convert|457.8|g|abbr=on}}. In the early 19th century, the {{lang|pt|arrátel}} was evaluated at {{convert|459|g|abbr=on}}.<ref>Luís Seabra Lopes, {{lang|pt|"As Pilhas de Pesos de Dom Manuel I: Contributo para a sua Caracterização, Inventariação e Avaliação", Portugalia: Nova Série}}, vol. 39, Universidade do Porto, 2018, p. 217-251.</ref>

In the 15th century, the {{lang|pt|arrátel}} was of 14 ounces of {{lang|pt|Colonha}} or {{convert|400.6|g|abbr=on}}. The Portuguese {{lang|pt|libra}} was the same as 2 {{lang|pt|arráteis}}. There were also {{lang|pt|arráteis}} of 12.5 and 13 ounces and {{lang|pt|libras}} of 15 and 16 ounces. The {{lang|pt|Troyes}} or {{lang|pt|Tria}} standard was also used.<ref>Luís Seabra Lopes, {{lang|pt|"Sistemas Legais de Medidas de Peso e Capacidade, do Condado Portucalense ao Século XVI", Portugalia: Nova Série}}, vol. 24, 2003, p. 113-164.</ref>

=== 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 ({{convert|490|g|abbr=on}}). It may have been derived from the [[#French livre|French livre poids de marc]].<ref>{{cite web |url=http://www.sizes.com/units/pound_jersey.htm|title=Jersey pound|author=Sizes, Inc. |access-date=12 August 2006 |date=28 July 2003}}</ref>

=== 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 {{convert|600-800|g|abbr=on}}).

=== 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 language|German]], the term is {{lang|de|Pfund}}, in [[French language|French]] {{lang|fr|livre}}, in Dutch {{lang|nl|pond}}, in [[Spanish language|Spanish]] and [[Portuguese language|Portuguese]] {{lang|pt|libra}}, in [[Italian language|Italian]] {{lang|it|libbra}}, and in [[Danish (language)|Danish]] and [[Swedish language|Swedish]] {{lang|sv|pund}}.

Though not from the same linguistic origin, the Chinese {{Transliteration|zh|jīn}} ({{lang|zh|斤}}, also known as the "[[catty]]") in [[mainland China]] has a modern definition of exactly {{convert|500|g|abbr=on}}, divided into 10 {{Transliteration|zh|liǎng}} ({{lang|zh|两}}). Traditionally around {{convert|600|g|abbr=on}}, the {{Transliteration|zh|jin}} 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 {{convert|604.78982|g|abbr=on}} in weight precisely.

Hundreds of older pounds were replaced in this way. Examples of the older pounds are one of around {{convert|459-460|g|2|abbr=on}} in Spain, Portugal, and Latin America; one of {{convert|498.1|g|abbr=on}} 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 [[gram]]s and [[kilogram]]s. 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]].<ref>{{cite web | url = http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:1980L0181:20090527:EN:PDF| author = The Council of the European Communities | title = Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC | date=27 May 2009 | access-date=14 September 2009}}</ref>

== Use in weaponry ==
<!--NOTE TO EDITORS: This section is externally linked to from [[Carronade]]. Please do not delete or rename without fixing the referring link(s).
-->
Smoothbore cannon and [[carronade]]s are currently 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; 60-pounders and 68-pounders also exist,  along with other nonstandard weapons using the same scheme. Before the introduction of the metric system, countries that produced their own artillery generally used their national pound for these designations. See [[Carronade#Ordnance|carronade]].

A similar definition, using [[lead]] balls, exists for determining the [[gauge (bore diameter)|gauge]] of [[shotgun]]s and [[shotgun shell]]s.

== See also ==
* [[Pound (force)|Pound-force]]
* [[Slug (unit)]]

== Notes ==
{{notelist}}

== References ==
<!-- ----------------------------------------------------------
 See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for a
 discussion of different citation methods and how to generate
 footnotes using the <ref>, </ref> and <reference /> tags
----------------------------------------------------------- -->
{{reflist}}

== External links ==
{{Wiktionary|pound}}

=== Conversion between units ===
* [https://www.nist.gov/pml/nist-guide-si-appendix-b9-factors-units-listed-kind-quantity-or-field-science U.S. National Institute of Standards and Technology Special Publication 811] {{Webarchive|url=https://web.archive.org/web/20171014051437/https://www.nist.gov/pml/nist-guide-si-appendix-b9-factors-units-listed-kind-quantity-or-field-science |date=14 October 2017 }}
* [https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-130 National Institute of Standards and Technology Handbook 130]

{{Imperial units}}
{{United States Customary Units}}
{{Authority control}}

{{DEFAULTSORT:Pound}}
[[Category:Customary units of measurement in the United States]]
[[Category:Imperial units]]
[[Category:Units of mass]]
[[Category:Metricated units]]