Troy ounce vs ounce
Every gold, silver, platinum and palladium price you see is quoted per troy ounce. A troy ounce weighs 31.1035 grams. The ounce on your kitchen scale weighs 28.3495 grams. Mixing them up is the most common reason a scrap gold estimate comes out wrong.
| Unit | Equals |
|---|---|
| 1 troy ounce | 31.1035 grams |
| 1 troy ounce | 1.0971 avoirdupois (regular) ounces |
| 1 troy ounce | 20 pennyweights (dwt) |
| 1 troy ounce | 480 grains |
| 1 avoirdupois ounce | 0.9115 troy ounces, or 28.3495 grams |
| 1 gram | 0.03215 troy ounces |
| 1 pennyweight | 1.5552 grams |
| 1 kilogram | 32.1507 troy ounces |
| 1 troy pound | 12 troy ounces, or 373.24 grams |
| 1 avoirdupois pound | 14.5833 troy ounces, or 453.59 grams |
| 1 tola | 11.6638 grams, or 0.375 troy ounces |
Where the troy ounce comes from
The name traces to Troyes, a market town in France that hosted big trade fairs in the Middle Ages. Merchants there used a standard weight for precious goods, and England was weighing gold and silver in troy units by the 1400s.
Most of the world went metric, but bullion didn't. Exchanges, refiners and mints still quote in troy ounces, and the US, UK and much of the world price precious metals that way. Gram and kilogram prices are just the ounce price converted.
In everyday writing people drop the word "troy." If someone quotes gold per ounce, they mean the troy ounce.
| Product | Weight | Where you see it |
|---|---|---|
| 1 troy ounce coin or bar | 31.1 g | Gold Eagles, Maple Leafs, Krugerrands (gold content) |
| 10 troy ounce bar | 311 g | Common silver and gold bar size in North America |
| 1 kilo bar | 1,000 g = 32.15 oz | Popular in Asia and with larger investors |
| 10 tola bar | 116.6 g = 3.75 oz | Sold across India, Pakistan and the Gulf |
| London Good Delivery bar | About 400 oz (350 to 430 oz) | The bar banks trade and central banks hold |
Common questions
- Is a troy ounce heavier than a regular ounce?
- Yes. A troy ounce is 31.1035 grams and a regular (avoirdupois) ounce is 28.3495 grams, so the troy ounce is about 9.7% heavier.
- Then why is a troy pound lighter than a regular pound?
- A troy pound has 12 troy ounces (373 grams), while a regular pound has 16 smaller ounces (454 grams). The troy ounce is bigger, but the troy pound has fewer of them.
- Can I weigh gold on a kitchen scale?
- You can, but set it to grams. A kitchen scale's ounce setting uses avoirdupois ounces, so reading it as troy ounces makes your gold look about 10% heavier than it is.