Avoirdupois

200 - gram balance scales

Bascule décimale, musée André Voulgre

File:English mass units short.png

English mass units short

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comparison of pounds

Avoirdupois is a system of weight measurement that is part of the imperial system of measurements, which is used primarily in the United States, and to a lesser extent in the United Kingdom, and other Commonwealth countries. The avoirdupois system is based on a pound of 16 ounces, and an ounce of 16 drams. It is distinct from other weight systems such as the troy weight system, which is used for precious metals, and the apothecaries' system, which was historically used in pharmacy.

History[edit | edit source]

The term "avoirdupois" comes from Middle English, derived from the Old French words aveir de pois ("goods of weight") and refers to goods that were sold by weight. The system has been used in England since around the 14th century. It was standardized in the 16th century by Henry VIII, who established the avoirdupois pound as consisting of 7,000 troy grains. The system was further refined and spread throughout the British Empire, becoming the standard system of weight in many parts of the world.

Units[edit | edit source]

The basic unit of the avoirdupois system is the pound, which is divided into 16 ounces. The system also includes larger and smaller units, such as:

Grain (the smallest unit, which is the same for both avoirdupois and troy weights)
Dram (1/16 of an ounce)
Ounce (1/16 of a pound)
Pound (the base unit)
Stone (14 pounds, not commonly used in the US)
Quarter (28 pounds, or 2 stones)
Hundredweight (112 pounds in the UK, 100 pounds in the US)
Ton (2,240 pounds in the UK, known as the long ton; 2,000 pounds in the US, known as the short ton)

Usage[edit | edit source]

Today, the avoirdupois system is primarily used in the United States for measuring body weight, the weight of groceries, and other items for commercial and household purposes. It is also used to some extent in the United Kingdom and Canada, although these countries have officially adopted the metric system for most legal measures of weight.

Comparison with Other Systems[edit | edit source]

The avoirdupois system is one of several systems of weight used around the world. It is different from the troy weight system, which is used for precious metals and gemstones, and the apothecaries' system, which was traditionally used in pharmacies. The troy pound is heavier than the avoirdupois pound, but the troy ounce is lighter than the avoirdupois ounce. The apothecaries' system was officially abolished in the UK in 1971 in favor of the metric system, but the troy and avoirdupois systems are still used in certain contexts.

Conversion to Metric[edit | edit source]

Conversion between the avoirdupois system and the metric system is straightforward, with 1 avoirdupois pound equaling approximately 453.59237 grams. However, the use of the metric system for official purposes is encouraged in most countries, including those where the avoirdupois system is still in use for everyday purposes.

Avoirdupois Resources
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