Ounce-Gram Conversion
Also: Ounce to Gram, oz to g, Troy Ounce Conversion, ozt
The troy ounce is the international standard unit for precious metal prices and equals exactly 31.1034768 grams.
Anyone following precious metal prices will inevitably encounter two different units of weight: the price per troy ounce quoted on exchanges and the everyday gram. The conversion between the two is straightforward — but only if you know which "ounce" is meant. The unit converter converts any unit in seconds.
The Troy Ounce – Not to Be Confused with the Commercial Ounce
In the precious metals trade, only the troy ounce (abbreviated ozt or oz t) is used. It derives from the medieval Troy weight system, which originated in the French city of Troyes, and was established by the LBMA as the binding unit of price.
Alongside it exists the avoirdupois ounce (oz av), used in everyday Anglo-American life for food, postage, and other goods. It is lighter than the troy ounce:
| Unit | Grams | Usage |
|---|---|---|
| Troy ounce (ozt) | 31.1034768 g | Precious metals worldwide |
| Avoirdupois ounce (oz av) | 28.3495 g | Everyday use (USA, UK) |
| Difference | +2.754 g | Troy ounce is heavier |
Anyone who accidentally uses the avoirdupois ounce will underestimate the metal quantity by nearly 9.7 % — a significant error when buying or selling.
Conversion Formulas
Grams → Troy ounces: g ÷ 31.1034768 = ozt
Troy ounces → Grams: ozt × 31.1034768 = g
Practical reference values for quick mental arithmetic:
- 1 ozt ≈ 31.1 g (sufficient for rough estimates)
- 10 ozt ≈ 311 g (e.g. ten silver coins at 1 ozt each)
- 1 kg = 32.1507 ozt (relevant for kilo bars)
- 100 g = 3.2151 ozt (common bar denomination)
Why is the Troy Ounce Still the Standard?
The gold price and silver price have been quoted in troy ounces for centuries — the London gold market has used the unit since the 17th century, COMEX in New York since its founding in 1933, and the LBMA as a formal institution since 1987. All global reference prices, ETF valuations, futures contracts, and central bank reserves are based on this unit. A changeover would require a complete redesign of all international trading standards and is considered unrealistic.
Conversion for Common Coin and Bar Sizes
| Product | Nominal weight (ozt) | Actual weight (g) |
|---|---|---|
| Standard bullion coin | 1 ozt | 31.1035 g |
| Half ounce | 0.5 ozt | 15.5517 g |
| Quarter ounce | 0.25 ozt | 7.7759 g |
| Tenth ounce | 0.1 ozt | 3.1103 g |
| Small bar | 1 g | 0.03215 ozt |
| Bar | 5 g | 0.16075 ozt |
| Bar | 10 g | 0.32151 ozt |
| Bar | 100 g | 3.21507 ozt |
| Kilo bar | 1,000 g | 32.1507 ozt |
With the melt value calculator, entering the weight in grams is sufficient — the conversion to troy ounces and multiplication by the current spot price are performed automatically.
Fine Weight vs. Gross Weight
Important: the weight of a coin or bar in grams is the gross weight (total weight including alloy components). The fine weight — i.e. the amount of pure metal contained — is only obtained by multiplying by the fineness:
Fine weight (g) = Gross weight (g) × Fineness (e.g. 0.999)
A Krugerrand (22 karat, fineness 916.7 ‰) weighs approximately 33.93 g gross, but contains exactly 1 ozt = 31.1035 g of fine gold. The difference is contained in the copper alloy addition.
In Brief
The troy ounce at exactly 31.1034768 grams is the indispensable bridge unit between the international exchange price and the weight in hand. Anyone who fails to clearly distinguish grams from avoirdupois ounces will calculate incorrectly in the market. The unit converter handles this distinction automatically.