
Avoirdupois (;
abbreviated avdp.)
is a
measurement system of
weights that uses
pounds and
ounce
The ounce () is any of several different units of mass, weight, or volume and is derived almost unchanged from the , an Ancient Roman unit of measurement.
The avoirdupois ounce (exactly ) is avoirdupois pound; this is the United States ...
s as 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.
[ The '']International Avoirdupois Pound
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement. Various definitions have been used; the most common today is the international avoirdupois pound, which is leg ...
'' was 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, Australia, and some other former British colonies
Below are lists of the countries and territories that were formerly ruled or administered by the United Kingdom or part of the British Empire (including military occupations that did not retain the pre-war central government), with their independ ...
, despite their official adoption of the metric system
The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...
.
The avoirdupois weight system's general attributes were originally developed for the international wool trade in the Late Middle Ages
The late Middle Ages or late medieval period was the Periodization, period of History of Europe, European history lasting from 1300 to 1500 AD. The late Middle Ages followed the High Middle Ages and preceded the onset of the early modern period ( ...
, when trade was in recovery. It was historically based on a physical standardized pound or "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 stabilized and evolved, with only slight changes in the reference standard or in the prototype's actual mass.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 VII authorized its use as a standard, and ]Queen Elizabeth I
Elizabeth I (7 September 153324 March 1603) was Queen of England and Ireland from 17 November 1558 until her death in 1603. She was the last and longest reigning monarch of the House of Tudor. Her eventful reign, and its effect on history ...
acted 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 international SI ]metric system
The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...
standards.[ 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 the pound generally 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, the troy system, is generally used for precious materials. The modern definition of the avoirdupois pound (1 lb) is exactly ]kilogram
The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (m ...
s.
Etymology
is from Anglo-Norman French
Anglo-Norman (; ), also known as Anglo-Norman French, was a dialect of Old Norman that was used in England and, to a lesser extent, other places in Great Britain and Ireland during the Anglo-Norman period.
Origin
The term "Anglo-Norman" har ...
(later ), literally "goods of weight" (Old French , as verb meaning "to have" and as noun meaning "property, goods", comes from the Latin
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
, "to have, to hold, to possess something"; = "from"/"of", cf. Latin; = "weight", from Latin .) This term originally referred to a class of merchandise: , "goods of weight", things that were sold in bulk and were weighed on large steelyards or balances.
Only later did the term become identified with a particular ''system of units'' used to weigh such merchandise. Inconsistent orthography
An orthography is a set of convention (norm), conventions for writing a language, including norms of spelling, punctuation, Word#Word boundaries, word boundaries, capitalization, hyphenation, and Emphasis (typography), emphasis.
Most national ...
throughout history has left many variants of the term, such as and . (The Norman became the Parisian . In the 17th century was replaced with .)
The current spelling of the last word is in the current standard French orthography
French orthography encompasses the spelling and punctuation of the French language. It is based on a combination of phonemic and historical principles. The spelling of words is largely based on the pronunciation of Old French –1200 AD, and has ...
, but the spelling ''avoirdupois'' remained as is in the anglosphere.
History
The rise in use of the measurement system corresponds to the regrowth of trade during the High Middle Ages
The High Middle Ages, or High Medieval Period, was the periodization, period of European history between and ; it was preceded by the Early Middle Ages and followed by the Late Middle Ages, which ended according to historiographical convention ...
after the early crusades
The Crusades were a series of religious wars initiated, supported, and at times directed by the Papacy during the Middle Ages. The most prominent of these were the campaigns to the Holy Land aimed at reclaiming Jerusalem and its surrounding t ...
, 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 of Florence
Florence ( ; ) is the capital city of the Italy, Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in Metropolitan City of Florence, its metropolitan province as of 2025.
Florence ...
.
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 the Hanseatic League
The Hanseatic League was a Middle Ages, medieval commercial and defensive network of merchant guilds and market towns in Central Europe, Central and Northern Europe, Northern Europe. Growing from a few Northern Germany, North German towns in the ...
with a 16-ounce pound of grains and an 8-ounce mark. However, the main weight system, used for coinage and for everyday use, was based on the 12-ounce tower pound of grains. From the 14th century until the late 16th century, the system's basis and the prototype for today's international pound, the avoirdupois pound, was also known as the wool pound or the avoirdupois wool pound.
The earliest known version of the avoirdupois weight system had the following units: a pound of grains, a stone of 14 pounds, a woolsack of 26 stone, an ounce of pound, 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 entitled ''Tractatus de Ponderibus et Mensuris'' ("Treatise on Weights and Measures"). This document is listed in early statute books under the heading ''31 Edward I'' dated 2 February 1303. More recent statute books list it among statutes 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.
In the ''Tractatus'', 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.
The ''Tractatus'' and other "ancient units" were repealed by the Weights and Measures Act 1824 ( 5 Geo. 4. c. 74). The division and mass of the Avoirdupois units were not significantly changed, but they became tied to actual physical objects and (as a backup) definitions based on physical constants. These definitions proved insufficient for recreating the physical prototypes after the 1834 Houses of Parliament fire, and a new Weights and Measures Act 1855 was passed which permitted the recreation of the prototypes from recognized secondary standards. The Act of 1855 also made the avoirdupois pound the primary unit of mass.
Original Anglo-Norman French forms
These are the units in their original Anglo-Norman French
Anglo-Norman (; ), also known as Anglo-Norman French, was a dialect of Old Norman that was used in England and, to a lesser extent, other places in Great Britain and Ireland during the Anglo-Norman period.
Origin
The term "Anglo-Norman" har ...
forms:
Toward a uniformity of measures
Three major developments occurred during the reign of Edward III
Edward III (13 November 1312 – 21 June 1377), also known as Edward of Windsor before his accession, was King of England from January 1327 until his death in 1377. He is noted for his military success and for restoring royal authority after t ...
(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."
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."
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 ( sack 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 of Henry VIII
Henry VIII (28 June 149128 January 1547) was King of England from 22 April 1509 until his death in 1547. Henry is known for his Wives of Henry VIII, six marriages and his efforts to have his first marriage (to Catherine of Aragon) annulled. ...
(24 Hen 8 c. 3) made avoirdupois weights mandatory.
In 1588 Queen Elizabeth increased the weight of the avoirdupois pound to grains and added the troy grain to the avoirdupois weight system. Prior to 1588, the "part" ( ounce) was the smallest unit in the avoirdupois weight system. In the 18th century, the "part" was renamed "drachm".
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 for mass
Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...
es to be easily converted between them and stone. The following are the units in the British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies.
* British national identity, the characteristics of British people and culture ...
or imperial version of the avoirdupois system:
''Note:'' The plural form of the unit ''stone'' is either ''stone'' or ''stones'', but ''stone'' is most frequently used.
American customary system
The thirteen British colonies in North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
used 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 the stone
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition, and the way in which it is formed. Rocks ...
unit. In 1824 there was landmark new weights and measures legislation in the United Kingdom (Weights and Measures Act 1824) that the United States did not adopt. The International yard and pound
The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: Australia, Canada, New Zealand, South Africa, the United Kingdom and the United States ...
agreement brought the systems closer; for residual differences, see .
In the United States, quarters, hundredweights, and tons remain defined as 25, 100, and respectively. 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 measuring gunpowder
Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...
and smokeless powder charges. Historically, the dram ( grains; not to be mixed up with the apothecaries' dram of 60 grains) has also been used worldwide for measuring gunpowder charges, particularly for shotguns and large black-powder rifles.
See also
* Apothecaries' system
The apothecaries' system, or apothecaries' weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists."Medicinal-Gewicht, Apotheke ...
* Units of measurement in France
200px, Table of the measuring units used in the 17th century at region of southeastern France
France has a unique history of Unit of measurement, units of measurement due to its radical decision to invent and adopt the metric system after the F ...
* Imperial units
The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed thr ...
* Troy weight
Troy weight is a system of units of mass that originated in the Kingdom of England in the 15th century and is primarily used in the precious metals industry. The troy weight units are the grain, the pennyweight (24 grains), the troy ounce (20 ...
* United States customary units
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories since being standardized and adopted in 1832. The United States customary system developed from English units that ...
* Weighing scales
References
Notes
Citations
Sources
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External links
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{{United States Customary Units
Units of mass
Imperial units
Customary units of measurement in the United States
Customary units of measurement