Avoirdupois

200 - gram balance scales

Bascule décimale, musée André Voulgre

Avoirdupois

The avoirdupois system is a system of weights based on a pound of 16 ounces. It is the everyday system of weights used in the United States and is still widely used in the United Kingdom for measuring body weight and other commodities. The term "avoirdupois" is derived from Middle French "aveir de pois" (goods of weight) and refers to goods that are sold by weight.

History

The avoirdupois system originated in France and was first used in England in the late 13th century. It became the standard system of weights in the 14th century and was officially adopted in the United Kingdom in 1824 with the Weights and Measures Act 1824. The system was designed to be more practical for trade and commerce compared to other systems of the time.

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comparison of pounds

Units

The primary units of the avoirdupois system are the pound and the ounce. The system also includes the grain, dram, and stone.

• Pound: The pound is the base unit of the avoirdupois system and is defined as exactly 0.45359237 kilograms.
• Ounce: There are 16 ounces in a pound. One ounce is equal to 28.349523125 grams.
• Grain: The smallest unit in the system, with 7,000 grains in a pound.
• Dram: There are 256 drams in a pound, with one dram equal to 1.7718451953125 grams.
• Stone: Commonly used in the UK for measuring body weight, one stone is equal to 14 pounds.

Comparison with Other Systems

The avoirdupois system is distinct from the troy weight and apothecaries' weight systems, which are used for precious metals and pharmaceuticals, respectively. The troy pound is lighter than the avoirdupois pound, containing only 12 troy ounces, while the apothecaries' system uses different units such as scruples and drams.

Modern Usage

In the United States, the avoirdupois system is the standard for all weights and measures, except for precious metals, gemstones, and pharmaceuticals. In the United Kingdom, the system is still used for body weight and some other applications, although the metric system is now the official system of measurement.

Related Pages

• Pound (mass)
• Ounce
• Stone (unit)
• Troy weight
• Apothecaries' weight
• Metric system
• Weights and Measures Act 1824