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
Metrication in the United States fl oz, and 24 fl oz (355, 473, 591 and 710 mL) sizes. The half-liter water bottle (16.9 fl oz) has nearly replaced the 16 ounce size. 700 mL (23.6 fl oz) and one-liter sizes are also common, though 20 fl oz, and 24 fl oz sizes remain popular, particularly in vending machines. Attempts to sell 3- or 4-liter jugs of milk, instead of gallons (3.785 L), have been largely unsuccessful, and such bottles are rarely seen in the United States. Milk remains sold in binary divisions of the gallon, with half-pints, pints, quarts and half-gallons being the primary sizes.