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A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons (9.31 U.S. liquid gallons). It is used for volumes of dry commodities (not liquids), most often in agriculture. It is abbreviated as bsh. or bu. In modern usage, the dry volume is usually only nominal, with bushels referring to standard weights instead.
- 1 U.S. bushel = 8 corn/dry gallons = 2150.42 cu in ≈ 35.2391 litre ≈ 9.30918 wine/liquid gallons. The original definition was the volume of a cylinder 18.5 in (46.99 cm) in diameter and 8 in (20.32 cm) high, which gives an irrational number of cubic inches, but later this bushel was redefined as 2150.42 cubic inches, about 1 part per million less.
- 1 imperial bushel = 8 imperial gallons ≈ 36.3687 litres ≈ 2219.36 cu in
- 1 bushel = 4 pecks
- 4 bushels = 1 coomb
Use as unit of weight
Bushels are now most often used as units of mass or weight rather than of volume. The bushels in which grains are bought and sold on commodity markets or at local grain elevators, and for reports of grain production, are all units of weight. This is done by assigning a standard weight to each commodity that is to be measured in bushels. These bushels depend on the commodities being measured and the moisture content. Some of the more common ones are:
- Barley: 48 lb = 21.7724 kg
- Malted barley: 34 lb = 15.4221 kg
- Shelled maize (corn) at 15.5% moisture by weight: 56 lb = 25.4012 kg
- Wheat at 13.5% moisture by weight and soybeans at 13% moisture by weight: 60 lb = 27.2155 kg
Other specific values are defined (and those definitions may vary within different jurisdictions, including from state to state in the United States) for other grains, oilseeds, fruits, vegetables, coal, hair, and many other commodities.
Government policy in the United States is to phase out units such as the bushel and replace them with metric mass equivalents.
The bushel was originally a measure of capacity for grain. During the Middle Ages, the bushel of wheat was supposed to weigh 64 tower pounds, but when the tower system was abolished in the 16th century, it was described as 56 avoirdupois pounds. The bushel was rarely used in Scotland, Ireland or Wales during the Middle Ages.