A gallon is a measure of volume. It is in current use in the United States and still has limited use in many other English-speaking countries. Historically the gallon has had many different definitions, but there are three definitions in current use. These are the U.S. liquid gallon, the U.S. dry gallon and the Imperial (UK) gallon. Definitions U.S. liquid gallon is legally defined as 231 cubic inches, and is equal to 3.785411784 litres (exactly) or about 0.13368 cubic feet. This is the most c… (More on Gallon)