What Is a Troy Ounce?

Definition

A troy ounce (symbol ozt) is the unit used to weigh precious metals — gold, silver, platinum, and palladium. One troy ounce equals exactly 31.1034768 grams, almost always rounded to 31.1035 g.

The troy ounce belongs to the troy weight system, an older measurement standard kept alive specifically for the bullion and jewelry trades. When a price quote says "gold is $2,400 an ounce," the ounce in question is a troy ounce — not the ounce you use to weigh food or mail.

Troy Ounce vs Standard Ounce

The everyday ounce is the avoirdupois ounce, which weighs 28.3495 g. The troy ounce is heavier. Here is the direct comparison:

A troy ounce is roughly 10% heavier than a standard ounce — about 2.75 g more. That gap matters: an "ounce" of gold contains noticeably more metal than an "ounce" of sugar.

Here is the common point of confusion. While the troy ounce is heavier, the troy pound is actually lighter than a standard pound. A troy pound holds only 12 troy ounces (12 × 31.1035 g ≈ 373.24 g), whereas a standard pound holds 16 avoirdupois ounces (453.59 g). Fewer ounces wins out, so the troy pound comes in lighter.

Why Precious Metals Use Troy

The troy system traces back to medieval European trade, with the name commonly linked to the market town of Troyes in France. Long before national standards, merchants needed a single, agreed weight for gold and silver so coins and bullion could be traded across borders without dispute.

That need for consistency is why the troy ounce survived while most of the old systems faded. Every major exchange, mint, and refiner quotes precious metals in troy ounces, so a one-ounce gold bar means the same thing in London, New York, or Zurich. Keeping bullion weight separate from everyday avoirdupois weight also removes any ambiguity about exactly how much metal is changing hands.

Everyday Examples

Once you know the troy ounce, common precious-metal items make sense:

• 1 oz gold coin — an American Gold Eagle or Canadian Maple Leaf holds one full troy ounce (31.1035 g) of gold.
• Silver bars — sold in troy ounces too, with popular sizes of 1 ozt, 10 ozt, and 100 ozt.
• Spot prices — every gold and silver quote you see is per troy ounce, never per standard ounce.
• Kilo bars — a 1 kg gold bar equals about 32.15 troy ounces, which is why large bars are often listed in both grams and ozt.

To switch between troy ounces, grams, and standard ounces, use our weight converter for exact, instant results.