Weight Conversion Ounce-Gram
Also: Ounce to gram, oz to g, Troy ounce conversion, ozt
The troy ounce is the international standard unit for precious metal prices and corresponds exactly to 31.1034768 grams.
Anyone following precious metal prices inevitably comes across two different weight units: the price per troy ounce quoted on exchanges and the gram commonly used in everyday life. Converting between the two is simple – but only if you know which "ounce" is meant. In the unit converter any unit can be converted in seconds.
The Troy Ounce – Not to Be Confused with the Everyday Ounce
In precious metal trading, only the troy ounce (abbreviation ozt or oz t) applies. It derives from the medieval Troy weight system, which originated in the French town of Troyes, and was established by the LBMA as the binding pricing unit.
Alongside it exists the avoirdupois ounce (oz av), used in the Anglo-American everyday world for food, post and other goods. It is lighter than the troy ounce:
| Unit | Grams | Use |
|---|---|---|
| Troy ounce (ozt) | 31.1034768 g | Precious metals worldwide |
| Avoirdupois ounce (oz av) | 28.3495 g | Everyday (USA, UK) |
| Difference | +2.754 g | The troy ounce is heavier |
Anyone who accidentally calculates using the avoirdupois ounce underestimates the quantity of metal by almost 9.7 % – a considerable error when buying or selling.
Conversion Formulas
Grams → troy ounces: g ÷ 31.1034768 = ozt
Troy ounces → grams: ozt × 31.1034768 = g
Practical rules of thumb for quick mental arithmetic:
- 1 ozt ≈ 31.1 g (sufficient for rough estimates)
- 10 ozt ≈ 311 g (e.g. ten 1 ozt silver coins)
- 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 the silver price have been quoted in troy ounces for centuries – the London gold market has used the unit since the 17th century, the COMEX in New York since its founding in 1933, 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 regarded as 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 it is enough to enter the weight in grams – the conversion into troy ounces and the multiplication by the current spot price are carried out automatically.
Fine Weight vs. Gross Weight
Important: the weight of a coin or bar in grams is the gross weight (total weight including alloy content). The fine weight – that is, the amount of pure metal contained – only results from multiplication by the fineness:
Fine weight (g) = Gross weight (g) × Fineness (e.g. 0.999)
A Krugerrand (22 carat, fineness 916.7 ‰) weighs around 33.93 g gross, but contains exactly 1 ozt = 31.1035 g of fine gold. The difference lies in the copper added to the alloy.
In Brief
The troy ounce, at exactly 31.1034768 grams, is the indispensable bridging unit between the international exchange price and the weight in your hand. Anyone who does not cleanly separate the gram and the avoirdupois ounce is calculating past the market. The unit converter makes this distinction automatically.