The gallon is a unit of measurement for volume and fluid capacity in both the US customary units and the British imperial systems of measurement. Three significantly different sizes are in current use:the imperial gallon, defined as 4.54609 litres, which is or was used in the United Kingdom, Canada, and some Caribbean nations; the US gallon defined as 231 cubic inches, which is used in the US and some Latin American and Caribbean countries; and the US dry gallon ("usdrygal"), defined as 1⁄8 US bushel.
