A troy ounce is the unit used to weigh and price precious metals. It equals 31.1035 grams, about 10% more than the 28.35 gram avoirdupois ounce used for groceries in the US.
For the full conversion table and the history of the unit, read our troy ounce guide. This entry covers what the troy ounce means on a price list: fine weight, gross weight and the cost per ounce of pure gold.
Fine weight vs gross weight on US coins
Dealer listings show "1 oz", but that number usually means fine weight: the amount of pure metal. Gross weight includes any alloy. The 1 oz American Gold Eagle is the classic US example. It is struck in 22 karat gold (91.67%) with silver and copper added on top of one full troy ounce of gold, so the coin weighs about 33.93 grams in total (31.1035 / 0.9167). The 1 oz American Gold Buffalo is .9999 fine, so its gross and fine weights are almost the same.
Both coins carry exactly one troy ounce of gold, which is why their prices are compared against the same spot price. Only the fineness, durability and premium differ. Compare the lowest delivered price for a 1 oz Gold Eagle with the 1 oz Gold Buffalo offers from US dealers to see which one costs less per ounce today.
Junk silver is priced by troy ounce too
Pre-1965 US dimes, quarters and half dollars are 90% silver. A dime weighs 2.50 g, so it holds 2.25 g of silver, or 0.0723 troy oz. Ten dimes ($1 face value) contain about 0.723 troy oz of silver when unworn. Dealers quote "junk silver" per dollar of face value for this reason. Our silver melt value calculator does the conversion for you.
How to use troy ounces when you shop
- Always compare price per troy ounce of fine metal, not price per item.
- Check gram-denominated bars against the gold price per gram: a 1 oz bar is not the same as a 30 g bar.
- For fractional coins (1/10 oz, 1/4 oz) divide the price by the fraction to get the cost per ounce, then compare the premium.
Related terms
Spot Price Fineness Bullion Karat
FAQ
Where can I find a troy ounce conversion table?
Our troy ounce guide on the blog has the full conversion table and the history of the unit. This glossary entry focuses on fine weight when you compare coin prices.
Is a troy ounce heavier than a regular ounce?
Yes, a troy ounce is about 9.7% heavier than the ounce used for food and postage in the US.
Does a 1 oz American Gold Eagle contain a full ounce of gold?
Yes, it contains one troy ounce of pure gold, and the added silver and copper bring its total weight to about 33.93 grams.