capacity or volume

See also the calculators on the Capacities of tanks page.

Units of volume. Their dimension is Length, cubed.

Liquid and dry measure

Historically two distinct classes of capacity measures existed, one for liquids like cooking oil and wine, and the other for grains. From its inception the metric system did not make this distinction, and the British ended this distinction in in 1824. The United States continues to have two separate systems.

Stricken and heaped measure

An important consideration with dry measures is whether they are heaped or “stricken”, that is, leveled by running a straight object (a “strick”) over the rim of the container (as today one makes “level teaspoons” in the kitchen). The difference between heaped and stricken measure can be very large, and depends on how steeply the substance can be heaped before it avalanches (the maximum steepness is called the “angle of repose”) and on the proportions of the container. A pie pan will have a much greater heaped capacity than a tennis ball can with the same level capacity. That is why old laws defining units of capacity usually describe the size of the container, rather than simply giving the number of cubic inches. Governments have frequently attempted to forbid commerce by heaped measure, almost always to no avail.