Avoirdupois

Finely crafted pan balance or scales with boxed set of standardized gram weights sequenced in units of mass. Such scales are used to make the most accurate of fine measurements, such as in the needs of empirical chemistry.

Avoirdupois(/ˌævərdəˈpɔɪz,ˌævwɑːrdjuːˈpwɑː/;abbreviatedavdp.)is ameasurement systemofweightsthat usespoundsandouncesas units.It was first commonly used in the 13th century AD and was updated in 1959.

In 1959, by international agreement, the definitions of the pound and ounce became standardized in countries which use the pound as a unit of mass.TheInternational Avoirdupois Poundwas then created. It is the everyday system of weights used in the United States. It is still used, in varying degrees, in everyday life in the United Kingdom, Canada, New Zealand, Australia, and some otherformer British colonies,despite theirofficial adoptionof themetric system.

The avoirdupois weight system's general attributes were originally developed for the international wool trade in theLate Middle Ages,when trade was in recovery. It was historically based on aphysical standardized poundor "prototype weight" that could be divided into 16 ounces.There were a number of competing measures of mass, and the fact that the avoirdupois pound had three even numbers as divisors (half and half and half again) may have been a cause of much of its popularity, so that the system won out over systems with 12 or 10 or 15 subdivisions.The use of this unofficial system gradually stabilizedand evolved, with only slight changes in the reference standard or in the prototype's actual mass.

Robust weights like these hexagonal decimal-scaled antiques were used for trade into the late 20th century.

Over time, the desire not to use too many different systems of measurement allowed the establishment of "value relationships", with other commodities metered and sold by weight measurements such as bulk goods (grains, ores, flax) and smelted metals; so the avoirdupois system gradually became an accepted standard through much of Europe.

In England,Henry VIIauthorized its use as a standard, andQueen Elizabeth Iacted three times to enforce a common standard, thus establishing what became the Imperial system of weights and measures.Late in the 19th century various governments acted to redefine their base standards on a scientific basis and establish ratios between local avoirdupois measurements and internationalSImetric systemstandards.The legal actions of these various governments were independently conceived, and so did not always pick the same ratios to metric units for each avoirdupois unit. The result of this was, after these standardisations, measurements of the same name often had marginally different recognised values in different regions (although thepoundgenerally remained very similar). In the modern day, this is evident in the small difference between United States customary and British Imperial pounds.

An alternative system of mass, thetroy system,is generally used for precious materials. The modern definition of the avoirdupois pound (1 lb) is exactly0.45359237kilograms.

Etymology

The wordavoirdupoisis fromAnglo-Norman Frenchaveir de peis(lateravoir du pois), literally "goods of weight" (Old Frenchaveir,as verb meaning "to have" and as noun meaning "property, goods", comes from theLatinhabere,"to have, to hold, to possess something";de= "from" / "of", cf. Latin;peis= "weight", from Latinpēnsum.This term originally referred to a class of merchandise:aveir de peis,"goods of weight", things that were sold in bulk and were weighed on largesteelyardsor balances.

Only later did the term become identified with a particularsystem of unitsused to weigh such merchandise. Inconsistentorthographythroughout history has left many variants of the term, such ashaberty-poieandhaber de peyse.(TheNormanpeisbecame theParisianpois.In the 17th centurydewas replaced withdu.)

The current spelling of the last word ispoidsin the current standardFrench orthography,but the spellingavoirdupoisremained as is in the anglosphere.

History

The units first became used by wool traders in theKingdom of Englandand theLow Countriesduring the end of theHigh Middle Ages,as population growth and theRenaissancegave rise to an increasingly numerous town population and a newly established middle class.

The rise in use of the measurement system corresponds to the regrowth of trade during theHigh Middle Agesafter the earlycrusades,when Europe experienced a growth in towns, turned from the chaos of warlordism to long-distance trade, and began annual fairs, tournaments and commerce, by land and sea. There are two major hypotheses regarding the origins of the avoirdupois system. The older hypothesis is that it originated in France.A newer hypothesis is that it is based on the weight system ofFlorence.

The avoirdupois weight system is thought to have come into use in England around 1300.It was originally used for weighing wool. In the early 14th century several other specialized weight systems were used, including the weight system of theHanseatic Leaguewith a16-ounce pound of7200grainsand an 8-ounce mark.However, the main weight system, used for coinage and for everyday use, was based on the 12-ouncetower poundof5400grains.From the 14th century until the late 16th century, the system's basis and the prototype for today'sinternational pound,the avoirdupois pound, was also known as thewool poundor theavoirdupois wool pound.

The earliest known version of the avoirdupois weight system had the following units: a pound of6992grains, a stone of 14 pounds, a woolsack of 26 stone, an ounce of1⁄16pound, and finally, the ounce was divided into 16 "parts".

The earliest known occurrence of the word "avoirdupois" (or some variant thereof) in England is from a document entitledTractatus de Ponderibus et Mensuris( "Treatise on Weights and Measures" ). This document is listed in early statute books under the heading31 Edward Idated 2 February 1303. More recent statute books list it amongstatutes of uncertain date.Scholars nowadays believe that it was probably written between 1266 and 1303.Initially a royal memorandum, it eventually took on the force of law and was recognized as a statute by King Henry VIII and Queen Elizabeth I.

It was repealed by theWeights and Measures Act 1824(5 Geo. 4.c. 74). In theTractatus,the word "avoirdupois" refers not to a weight system, but to a class of goods, specifically heavy goods sold by weight, as opposed to goods sold by volume, count, or some other method. Since it is written in Anglo-Norman French, this document is not the first occurrence of the word in the English language.

Comparison of the relative sizes of avoirdupois, Troy, tower, merchant and London pounds.

Toward a uniformity of measures

Three major developments occurred during the reign ofEdward III(r. 1327–1377). First, a statute cited as 14 Edw 3 Stat. 1 c. 12 (1340) "Bushels and Weights shall be made and sent into every County."

& acorde qe deſore en auant vn meſure & vn pois ſoit parmy toute Engleterre & qe le Treſorer face faire certaines eſtandardz de buſſel de galon de poys darreiſne & les face mander en cheſcune countee par la ou tielx eſtandardz ne ſont pas auant ces hures mandez

(4) it is assented and accorded, That from henceforth one Measure and one Weight shall be throughout England; (5) and that the Treasurer cause to be made certain Standards of Bushels, Gallons, of Weights of Auncel, and send the same into every County where such Standards be not sent before this Time;

The second major development is the statute 25 Edw 3 Stat. 5 c. 9 (1350) "The Auncel Weight shall be put out, and Weighing shall be by equal Balance."

qe le ſak de leine ne poiſe qe vint & ſys peres & cheſcun pere poiſe quatorze livres

so that the Sack of Wooll weigh no more but xxvi. Stones, and every Stone to weigh xiv. l.

The third development is a set of 14th-century bronze weights at the Westgate Museum in Winchester, England. The weights are in denominations of 7 pounds (corresponding to a unit known as the clip or wool-clip), 14 pounds (stone), 56 pounds (4 stone) and 91 pounds (1⁄4sack or woolsack).The 91-pound weight is thought to have been commissioned by Edward III in conjunction with the statute of 1350, while the other weights are thought to have been commissioned in conjunction with the statutes of 1340. The 56-pound weight was used as a reference standard as late as 1588.

A statute ofHenry VIII(24 Hen 8 c. 3) made avoirdupois weights mandatory.

In 1588Queen Elizabethincreased the weight of the avoirdupois pound to7000grains and added the troy grain to the avoirdupois weight system. Prior to 1588, the "part" (1⁄16) was the smallest unit in the avoirdupois weight system. In the 18th century, the "part" was renamed "drachm".

Original forms

These are the units in their originalAnglo-Norman Frenchforms:

Table of mass units

Unit	Relative value	Notes
"part"	1⁄256	1⁄16once
once(ounce)	1⁄16
livre(pound)	1
pere(stone)	14
sak de leine(woolsack)	364	26peres

Post-Elizabethan units

In the United Kingdom, 14 avoirdupois pounds equal one stone. The quarter, hundredweight, and ton equal respectively, 28 lb, 112 lb, and 2,240 lb in order formassesto be easily converted between them and stone. The following are the units in theBritishorimperialversion of the avoirdupois system:

Table of mass units

Unit	Relative value	Metric value	Notes
dram or drachm (dr)	1⁄256	≈1.772 g	1⁄16oz
ounce (oz)	1⁄16	≈28.35 g	16 dr
pound (lb)	1	≈ 453.6 g	16 oz
stone (st)	14	≈ 6.350 kg	1⁄2qr
quarter (qr)	28	≈ 12.70 kg	2 st
long hundredweight (cwt)	112	≈ 50.80 kg	4 qr
ton (t) or long ton	2240	≈1016kg	20 cwt

Note:The plural form of the unitstoneis eitherstoneorstones,butstoneis most frequently used.

American customary system

Main article:United States customary units

Thethirteen British coloniesinNorth Americaused the avoirdupois system, but continued to use the British system as it was, without the evolution that was occurring in Britain in the use of thestoneunit. In 1824 there was landmark new weights and measures legislation in the United Kingdom that the United States did not adopt.

In the United States, quarters, hundredweights, and tons remain defined as 25, 100, and2000 lbrespectively. The quarter is now virtually unused, as is the hundredweight outside of agriculture and commodities. If disambiguation is required, then they are referred to as the smaller "short" units in the United States, as opposed to the larger British "long" units. Grains are used worldwide for measuringgunpowderand smokeless powder charges. Historically, the dram (27+11⁄32grains; not to be mixed up with theapothecaries' dramof 60 grains) has also been used worldwide for measuring gunpowder charges, particularly for shotguns andlarge black-powder rifles.

Table of mass units

Unit	Relative value	Metric value	Notes
grain (gr)	1⁄7000	≈64.80 mg	1⁄7000lb
dram (dr)	1⁄256	≈1.772 g	1⁄16oz
ounce (oz)	1⁄16	≈28.35 g	16 dr
pound (lb)	1	≈ 453.6 g	16 oz
quarter (qr)	25	≈ 11.34 kg	25 lb
short hundredweight (cwt)	100	≈ 45.36 kg	4 qr
ton (t) or short ton	2000	≈ 907.2 kg	20 cwt

See also

Main articles:Pound-mass,Pound-force,andPoundal

• Apothecaries' system
• Units of measurement in France
• Imperial units
• Troy weight
• United States customary units
• Weighing scales

References

Sources

• Erasmus, Desiderius (2003). Charles Garfield Nauert (ed.).The Correspondence of Erasmus Letters 1658 to 1801: January 1526-March 1527.Translated by Alexander Dalzell. University of Toronto Press.ISBN978-0-8020-4831-8.
• Marsh, Horace Wilmer; Marsh, Annie Griswold Fordyce (1912).Constructive text-book of practical mathematics.J. Wiley.
• Ruffhead, Owen (1763).The Statutes at Large.Vol. 1. London: Printed by Mark Baskett.
• Skinner, F.G. (1952). "The English Yard and Pound Weight".Bulletin of the British Society for the History of Science.1(7): 186.doi:10.1017/S0950563600000646.
• Wedgwood, Hensleigh(1882).Contested etymologies in the dictionary of the Rev. W. W. Skeat.Trübner & Co.

External links

• Chisholm, Hugh,ed. (1911)."Avoirdupois".Encyclopædia Britannica.Vol. 3 (11th ed.). Cambridge University Press. p. 66.
• A bronze Edward III standard weight of 14lb (1327-1377)
• A bronze Edward III standard weight of 91lb (1/4 sack) (1327-1377)