Ounce (oz)
Definition
The ounce (symbol oz) is a unit of mass in the imperial and US customary systems equal to exactly 28.349523125 grams, or 1/16 of an avoirdupois pound. It is the primary unit for retail food packaging, cosmetics, and postage in the United States.
History
The ounce comes from the Latin uncia, meaning one twelfth, originally one twelfth of a Roman libra. Medieval Europe split into a twelve-ounce troy pound, still used for precious metals, and a sixteen-ounce avoirdupois pound used for general goods.
The avoirdupois ounce was fixed by the 1959 international yard and pound agreement at exactly 1/16 of 0.45359237 kg. Calcflux's ounce refers to the avoirdupois unit. The troy ounce of 31.1034768 g, used for gold and silver, is a separate unit.
Standard reference
Defined as 1/16 of the international avoirdupois pound: exactly 28.349523125 g. NIST Special Publication 811 publishes the exact value.
Common conversions
| 1 oz | = 28.349523125 g |
|---|---|
| = 0.0283495 kg | |
| = 0.0625 lb |