Gallon is a measure of capacity containing 231 cubic inches or four quarts. The standard for the U.S. gallon is a volume of 3,785.307 cubic centimeters, 0.13368 cubic feet. The U.S. gallon of distilled water weighs 8.337 pounds (roughly 8.3 pounds) when measured at 15 °C. (59 °F.), relative humidity of 50 percent, and air pressure of 29.92 inches of mercury.
The British imperial gallon (also used in Canada) has a capacity of 4,546.1 cubic centimeters or 277.3 cubic inches. An imperial gallon of distilled water weighs 10 pounds at 15 °C. (59 °F.) The old English wine gallon was 231 cubic inches. In countries using the metric system, four liters would be the nearest convenient equivalent to the U.S. gallon.
