Gallon Gallon 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 litres (4 imperial quarts or 8 imperial pints), which is used in the United Kingdom, Canada, and some Caribbean nations; the US gallon defined as 231 cubic inches (4 US liquid quarts or 8 US liquid pints) or about , which is used in the US and some Latin American and Caribbean countries; and the least-used US dry gallon defined
Keg (approximately 82 liters/144 imperial pints) and 22 imperial gallon (approximately 100 liters/172 imperial pints) kegs, however owing to their size they are not so popular as manual handling is seen by some to be difficult, and as a result they tend to be used only for large-scale events and bars with high throughput. For bars that sell an excessive volume of beer there is the 36 imperial gallon (150 liter/260 imperial pint) keg, however due to its very large size few people can move them making it an impractical choice. In the U.S. as of 2005, there are 21 states