The gallon was a traditional British unit of capacity, which was the origin of both the British Imperial gallon and the United States customary gallon.

British traditional units of capacity varied in size, depending on the commodity being measured. Thus an ale gallon differed from a wine gallon, and the same applied to all the subdivisions and multiples of the gallon. In general, the gallon was a measure of some particular commodity that weighed 8 pounds, which made the pint weigh a pound. However, the ale gallon was 282 cubic inches, much larger than this might imply.

In the United States, the wine gallon of 231 cubic inches became the standard gallon for all liquid commodities, and the gallon was eliminated as a standard for measuring dry commodities in favor of the bushel, which was based on the bushel used in measuring wheat or barley. Since the grain measures were not identical to the wine measures, this meant that corresponding subdivisions of United States liquid and dry measure were unequal; however, the only subdivisions which are commonly used are the pint and quart.

In Britain, the 1824 Weights and Measures Act established a new Imperial gallon, considerably larger than the United States customary gallon and indeed larger than most gallons that had existed in Britain at the time, defined as the volume of water weighing 10 pounds at 62° F. It was close to the old ale gallon, however, measuring slightly over 277 cubic inches.

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