Troy Ounce vs. Regular Ounce
When people say "ounce," they usually mean an avoirdupois ounce — the one used for measuring food, body weight, and everyday items. But the precious metals industry exclusively uses the troy ounce, which is about 10% heavier.
| Troy Ounce | Avoirdupois (Regular) Ounce | |
|---|---|---|
| Weight | 31.1035 grams | 28.3495 grams |
| Used for | Gold, silver, platinum, palladium | Food, body weight, everything else |
| Per pound | 12 troy oz = 1 troy pound | 16 oz = 1 avoirdupois pound |
| Abbreviation | oz t (or just "oz" in metals context) | oz |
A troy ounce is 2.75 grams heavier than a regular ounce. If you weigh silver on a kitchen scale (which uses avoirdupois ounces) and multiply by the spot price, your calculation will be ~10% too low. Always convert to troy ounces first or use grams directly.
Why Do Precious Metals Use Troy Ounces?
The troy weight system dates back to the Middle Ages, originating from the French trading city of Troyes. Merchants in Troyes used this system for trading precious metals and gems at annual fairs. The system was adopted by the English in the 1400s and has been the global standard for precious metals ever since.
Quick Conversion Reference
| From | To | Multiply by |
|---|---|---|
| Troy ounces | Grams | 31.1035 |
| Grams | Troy ounces | 0.03215 |
| Regular ounces | Troy ounces | 0.9115 |
| Troy ounces | Regular ounces | 1.0971 |
| Kilograms | Troy ounces | 32.1507 |
| Pennyweight (dwt) | Troy ounces | 0.05 |
| Tola | Troy ounces | 0.375 |
Why This Matters When Buying or Selling Silver
- Price quotes — "Silver is $32.50 per ounce" ALWAYS means per troy ounce
- Weighing at home — Kitchen scales use regular ounces; use grams and convert instead
- Dealer negotiation — Make sure you and the dealer are using the same unit
- Silver bars — A "1oz silver bar" contains 1 troy ounce (31.1g), not 28.3g
Related Weight Units in Precious Metals
Pennyweight (dwt)
Common in the jewelry industry. 20 pennyweight = 1 troy ounce. Jewelers often weigh items in dwt because it provides a finer scale for small items.
Tola
Used in South Asia (India, Pakistan, Bangladesh) for precious metals. 1 tola = 11.6638 grams = 0.375 troy ounces. See our converter for easy tola conversions.
Grain
The smallest traditional unit. 480 grains = 1 troy ounce. Rarely used in modern trading but appears in some historical references.