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
Pint cider may be sold by the imperial pint in perpetuity, and in public houses can only be sold in a third of a pint, two-thirds of a pint or multiples of half a pint, which must be served in stamped measured glasses or from government-stamped meters. Since the majority of countries in the world no longer use American or British imperial units, and most are non-English speaking, a "pint of beer" served in a tavern outside the United Kingdom and the United States may be measured by other standards. In Commonwealth countries it may be a British imperial pint of