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
Imperial and US customary measurement systems 277.42 cubic inches (4.546 litres). Twenty imperial fluid ounces make an imperial pint, the imperial fluid ounce being 0.96 US fluid ounces. The US Customary system of units makes use of set of dry units of capacity that have a similar set of names to those of liquid capacity, though different volumes - the dry pint having a volume of 33.6 cubic inches (550 ml) against the US fluid pint's volume of 28.875 cubic inches (473 ml) and the imperial pint of 34.68 cubic inches (568 ml). The imperial system of measure does not have an equivalent to the US