The
troy ounce is the traditional unit of mass for precious
metals. It derives from the
troy system of mass, which dates back to before the
time of
William the Conqueror. Its name is thought to derive from the town of
Troyes in
France. 1 troy ounce is defined as exactly 480 grains, where 1 grain is exactly 64.79891
milligrams, hence 1 troy ounce is exactly 31.1034768
grams.
The symbol for ounce is ℥
Note: The troy ounce is about 10% more than the more common ounce defined by the avoirdupois system of mass, which is 28.3 g. There are also two versions of the fluid ounce, units of volume, of 28.4 and 29.6 ml.
See also Conversion of units.
