Avoidupois', or AVERDEPOIS, is the name given to the system of weights and measures applied in Great Britain and Ireland to all goods except the precious metals and precious stones and medicines. The word is derived from the old French avoir de pois ('goods of weight'), the du for de being a corruption; the word avoir or avoir being a noun meaning 'property,' 'goods.' The correct spelling is the form averdepois, in use in the 17th century.
The grain is the foundation of the avoidupois system, as well as of the troy. A cubic inch of water, at standard temperature, weighs 252.458 grains. Of the grains so determined, 7000 make a pound avoidupois, and 5760 a pound troy (see WEIGHTS AND MEASURES).—The avoidupois pound is divided into 16 ounces, and the ounce into 16 drams. A dram, therefore, contains 27½ grains, and an ounce 437½ grains.
TABLE OF AVOIDUPOIS WEIGHT.
| 27½ grains | are 1 dram | 1 dr. |
| 16 drams or drachms | " 1 ounce | 1 oz. |
| 16 ounces | " 1 pound | 1 lb. |
| 28 pounds | " 1 quarter | 1 qr. |
| 4 quarters | " 1 hundredweight | 1 cwt. |
| 20 hundredweight | " 1 ton | 1 ton. |
A cubic foot of water weighs 997.14 ounces avoidupois, or nearly 1000 ounces, which gives an easy rule for determining the weight of a cubic foot of any substance from its specific gravity. Avoidupois is the weight used in the United States of North America, where, however, a cwt., or cental, of only 100 lb. has come into general use, and a ton of 2000 lb.