Unit of weight in the avoirdupois system, the traditional European system of weight, which was incorporated into the British Imperial system and the U.S. system of weights and measures (see measurement). The ounce is equal to 1/16 lb (437.5 grains). In the troy and apothecaries' systems (two other traditional systems of weight), it is equal to 1/12 troy or apothecaries' lb (480 grains). The avoirdupois ounce is equal to 28.35 g, the troy ounce to 31.1 g. As a unit of volume, the fluid ounce is equal to 1/16 of a pint (29.57 ml) in the U.S. system, and to 1/20 of a pint (28.41 ml) in the British Imperial system. Seealso gram, International System of Units, metric system, pound.
Learn more about ounce with a free trial on Britannica.com.
|ounce variant||mass in grams||mass in grains|
|International avoirdupois ounce||28.35||437.5|
|International troy ounce||31.1034768||480|
|Maria Theresa ounce|
|Dutch metric ounce|
|Chinese metric ounce|
Note: The grain values for the Maria Theresa, Dutch and Chinese|
ounces are rounded to the nearest thousandth of a grain.
In 1958 the United States and countries of the Commonwealth of Nations agreed to define the international avoirdupois pound to be exactly 0.45359237 kilograms. Consequently, since 1958, the international avoirdupois ounce is exactly 28.349523125 grams by definition.
The ounce is commonly used as a unit of mass in the United States. While imperial units have been officially abolished in the United Kingdom, the ounce remains a familiar unit, especially amongst older people.
For historical measurement of gold,
The Dutch have redefined their ounce (in Dutch, ons) as 100 grams . The Dutch's metric values, such as 1 ons = 100 grams, is inherited, adopted and taught in Indonesia since elementary school. It is also formally written in Indonesian national dictionary (Kamus Besar Bahasa Indonesia) and elementary school's formal manual book.