Comparison of the imperial and US customary measurement systems adopted a system based on the 231-cubic-inch wine gallon for all fluid purposes. This became the US fluid gallon. Both the imperial and US fluid gallon are divided into 4 quarts, 8 pints or 32 gills. However, whereas the US gill is divided into 4 US fluid ounces, the imperial gill is divided into 5 imperial fluid ounces. So whilst the imperial gallon, quart, pint and gill are about 20% larger than their US fluid measure counterparts, the fluid ounce is about 4% smaller. Note that one avoirdupois ounce of water has an approximate volume of one imperial fluid ounce
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