Troy ounce

A troy ounce is the standard weight unit for precious metals, equal to 31.1035 grams, heavier than the ordinary avoirdupois ounce used for most other goods.

Precious metals are weighed and priced using the troy ounce, a unit equal to 31.1035 grams, which is heavier than the more familiar avoirdupois ounce used to weigh most other goods. The distinct unit survives from historical trade in gold and silver and remains the standard across bullion markets worldwide.

Gold, silver, platinum, and palladium prices are all quoted per troy ounce, and confusing it with the ordinary ounce would meaningfully misstate a metal’s value, since the two units are different enough that the mix-up matters. A benchmark gold price, jewelry pricing, and central bank reserve figures are all expressed in troy ounces, making it one of the few specialized units that appears consistently across an entire market.