Troy Ounce

A troy ounce is the standard unit of weight used for gold, silver, platinum, and palladium, equal to 31.1034768 grams. It is heavier than the avoirdupois ounce used for groceries and shipping, which is about 28.35 grams, so a troy ounce of gold weighs roughly ten percent more than an ounce of anything weighed the ordinary way.

Every precious metals quote you see is per troy ounce, so the unit matters whenever you are converting between weight and value. The spot price of gold is the price of one troy ounce of pure gold.

Two distinctions come up constantly. The first is gross weight versus metal content. A one-ounce American Gold Eagle contains one full troy ounce of gold but weighs more than that overall, because it is 22 karat and alloyed with silver and copper. An American Gold Buffalo is .9999 fine, so its gross weight and its gold content are effectively the same. The second is partial ounces. Morgan and Peace dollars weigh 26.73 grams gross and contain .7734 troy ounces of silver, less than a full ounce despite being large coins. Fractional Gold Eagles work the same way, in halves, quarters, and tenths of an ounce of gold. Anyone buying bullion by weight should know which figure is being quoted.

A Texas Bullion Exchange specialist can confirm the metal content of anything you are weighing.