Troy Ounce

The standard unit of weight for precious metals, equal to approximately 31.1 grams — distinct from the avoirdupois ounce (28.35 grams) used for everyday goods.

All precious metals prices are quoted in troy ounces, not the avoirdupois ounces used for everyday goods. The distinction matters: a troy ounce is approximately 31.1035 grams, while an avoirdupois ounce is 28.3495 grams — a difference of roughly 10%. A "10-ounce silver bar" contains 10 troy ounces (311 grams) of silver, not 10 avoirdupois ounces. Confusing the two creates meaningful valuation errors when converting between price and weight.

The troy ounce traces its history to Troyes, a medieval French trading city that became a major center for precious metals commerce. The system spread through European trade and was standardized in the 19th century. Twelve troy ounces equal one troy pound, compared to 16 avoirdupois ounces in an avoirdupois pound. The troy system has no everyday use outside precious metals and certain pharmaceutical and gemstone applications.

For investors, the troy ounce is simply the universal unit of account for gold and silver. When a spot price of $30/oz silver is quoted, that is $30 per troy ounce. When a COMEX silver contract specifies 5,000 ounces, those are 5,000 troy ounces (approximately 155.5 kilograms of silver). When a coin dealer lists a "1-ounce silver round," it contains exactly one troy ounce. Understanding this eliminates a common source of confusion when converting between metric weights commonly used in Asian markets: 1 kilogram equals 32.1507 troy ounces.

This definition is for informational and educational purposes only. Nothing on Finance Compass constitutes financial, investment, or trading advice. Always conduct your own research and consult a qualified professional before making financial decisions.