In
US customary units, three units of volume exist both in a dry and a liquid version, with the same name but different values—the dry
barrel, the dry
quart, and the dry
pint—while the
bushel and
peck are only used for dry goods.
Imperial units of volume are the same for both dry and liquid goods, and have a different value from both the dry and liquid US versions of the pint and quart: an imperial pint and quart are 20.095% larger than their US liquid counterparts and 3.21% larger than their US dry counterparts, whereas the imperial peck and imperial bushel were deleted from the relevant UK statute in 1968. Many of the units are associated with particular goods, and there are also special measures for specific goods, such as the
cord of wood, the sack, the
bale of wool or cotton, the box of fruit,
etc. Because it is difficult to measure actual volume and easy to measure mass, many of these units are now also defined as units of mass, specific to each commodity, so a bushel of apples is a different weight from a bushel of wheat (weighed at a specific moisture level). Indeed, the bushel, the best-known unit of dry measure as the quoted unit in
commodity markets, is a unit of mass in those contexts. Conversely, the
ton used in specifying
tonnage and in freight calculations is often a volume measurement rather than a mass measurement. In US
cooking, dry and liquid measures are the same: the
cup, the
tablespoon, the
teaspoon. In the US, the dry quart and dry pint are exactly larger than their liquid counterparts, while the dry barrel is exactly smaller than the fluid barrel, except for barrels of beer (dry barrels are exactly smaller) and barrels of oil (dry barrels are exactly smaller). ==Struck and heaped measurement==