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The international avoirdupois ounce (or simply "ounce") is a unit of mass in the Imperial and US customary systems of units equal to 0.028349523125 kilograms (1 oz = 0.028349523125 kg), the base unit of mass in the International System of Units (SI).
One ounce (oz) is also equal to 28.349523125 grams (g), or 28,349.523125 milligrams (mg) or 28.349523125 × 106 micrograms (μg) (SI units of mass), or 0.0625 pounds (lb), or 0.9114583 troy ounces (oz t) or 437.5 grains (gr), which are US customary / Imperial units of mass.
The ounce definition varies depending on the system of units used, as follows:
- The avoirdupois ounce (or simply "ounce"), equal to 0.0625 pounds
- The troy ounce, equal to 0.0685714286 pounds
- The Apothecaries' ounce, equal to 0.0685714286 pounds
- The Dutch metric ounce, equal to 0.220462262 pounds
- The Spanish ounce, equal to 0.0633829004 pounds
- The Chinese metric ounce, equal to 0.110231131 pounds
- The Maria Theresa ounce, equal to 0.0618767022 pounds
The ounce is commonly used as a unit of mass / weight in the United States and the United Kingdom.
The abbreviation "oz" for ounce comes from the old Italian word "onza".
Also called: ounce (plural: ounces, symbol: oz)