Troy Ounce
Also: Troy Ounce, oz t, Fine Ounce, ozt
The standard weight unit used worldwide in precious metal trading: one troy ounce equals exactly 31.1034768 grams of pure metal.
The troy ounce (abbreviated oz t or ozt) is the internationally accepted unit of measure in which gold, silver, platinum and palladium are quoted and traded. A single troy ounce weighs precisely 31.1034768 grams. It is worth stressing that the troy ounce always describes the quantity of pure metal, never the gross weight of a piece of jewellery or a coin containing base-metal alloy.
A troy ounce is not an ordinary ounce
The ounce most people meet in everyday life is the avoirdupois ounce of roughly 28.35 grams, used for weighing groceries and post. The troy ounce is noticeably heavier and descends from a medieval system of weights associated with the French town of Troyes. Anyone comparing quotes needs to keep this distinction in mind: in the bullion trade a stated "price per ounce" practically always refers to the troy ounce of 31.1035 grams.
Why the troy ounce sits at the heart of pricing
The current gold price and the silver price are quoted on global markets in US dollars per troy ounce. To translate that headline figure into the value of a specific bar or coin, you simply convert to grams:
- 1 troy ounce = 31.1034768 g
- 1 gram = 0.0321507 troy ounces
- 1 kilogram = 32.1507 troy ounces
A familiar 100-gram gold bar therefore holds about 3.215 troy ounces of fine gold. The quickest way to work out the exact euro equivalent is with the gold calculator or, for any unit you like, the unit converter.
The troy ounce in bullion coins
Many of the best-known bullion coins, such as the Krugerrand, the Maple Leaf and the Vienna Philharmonic, each contain exactly one troy ounce of fine gold. In coins that use a copper alloy (the Krugerrand being a classic example) the total weight comes out above 31.1 grams because the added metal is included, yet the fine-gold content remains precisely one ounce. Beyond the full ounce, fractional sizes are common too: 1/2 oz, 1/4 oz, 1/10 oz and occasionally 1/20 oz.
In short
The troy ounce is the pivot around which every precious metal quote turns. Once you are comfortable with it, converting between world market prices, bar weights and coin fractions becomes effortless, and you can tell at a glance whether an offer has been fairly priced.