The derived SI unit for volumes is the cubic metre. The metric system also includes the litre (L) (international spelling) or liter (American spelling) defined as one cubic decimetre. The litre was introduced in France 1795 as one of the new republican units and defined as one cubic decimetre which by the definition then equaled one kilogram of water at 0 °C.

U.S. liquid units

Fluids and dry goods have similar units but with different magnitude. For liquids, one U.S. fluid ounce equals a 1/16 of a pint, 1/32 of a quart and 1/128 of a gallon. Originally the fluid ounce was the same as an avoirdupois ounce (in terms of weight), but since it is defined as 1/128 of a U.S. gallon today a fluid ounce of water weighs about 1.041 ounces avoirdupois.

The acre-foot is a unit commonly used to measure large amounts of water such as reservoirs, canals and river flows. One acre-foot is the volume occupied by an acre of area to depth of one foot.

British Imperial Liquids and Dry

In 1824, the Imperial gallon replaced the various gallons used in the British Empire. Originally defined as the volume of 10 pounds of water it is now since 1985 linked to the metric system as equaling 4.54609 L.

One Imperial gallon (gal) equals 4 quarts (qt), which in turn equals 2 pints (pt), which is made up of 4 gills (gi) which are defined as 5 fluid ounces (fl oz).

Japanese Shakkan-hō (尺貫法)

The metric system introduced in 1924 has replaced the traditional Japanese Shakkan-hō (尺貫法) system but for example the 合 is still used when serving sake.