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
Gallon when using a gallon to specify a quantity of material for purposes of trade, it is common to define the temperature at which the material will occupy the specified volume. For example, the volume of petroleum products and alcoholic beverages are both referenced to in government regulations. This dry measure is one-eighth of a US "Winchester" bushel of cubic inches; it is therefore equal to exactly 268.8025 cubic inches or about . The US dry gallon is not used in commerce, and is not listed in the relevant statute, which jumps from the dry quart to the peck. Gallons used