Troy Ounces to Grams Converter

What Is a Troy Ounce?

A troy ounce is the standard unit of weight for precious metals such as gold, silver, and platinum. It equals exactly 31.1035 grams, making it roughly 10% heavier than the more common avoirdupois ounce (28.3495 g) used for everyday items in the United States and United Kingdom.

The troy system dates back to the Middle Ages and is named after Troyes, France, a major trading hub. It remains the global standard for precious metals pricing. When you see a gold spot price quoted “per ounce,” it always refers to a troy ounce, not a regular ounce.

Troy Ounce vs. Avoirdupois Ounce

The avoirdupois ounce (abbreviated “oz”) weighs 28.3495 grams and is part of the 16-ounce-per-pound system used for food, postal, and general measurement in the U.S. The troy ounce (abbreviated “ozt”) weighs 31.1035 grams. There are only 12 troy ounces in a troy pound, compared to 16 avoirdupois ounces in a standard pound.

This distinction matters when buying or selling precious metals. If you accidentally use the wrong ounce in your calculations, you could be off by about 10% — a significant error when dealing with gold or silver at thousands of dollars per ounce.

Why Do Precious Metals Use Troy Ounces?

Precious metals have been measured in troy ounces for centuries to maintain consistency across international markets. All major exchanges — COMEX, LBMA, and the Shanghai Gold Exchange — quote prices per troy ounce. This universal standard ensures traders, refiners, and investors worldwide are using the same unit, reducing confusion and errors in high-value transactions.