Troy Ounce vs Ounce: How Many Grams in an Ounce of Gold?

There are 31.1035 grams in an ounce of gold. That is the troy ounce, the only ounce the gold market uses. The everyday ounce on a kitchen scale is the avoirdupois ounce, 28.3495 grams, about 9.7% lighter. Confusing them is the commonest weight error in precious metals, and at today's prices it costs hundreds of dollars. The troy ounce to grams calculator converts any weight instantly.

How Many Grams in an Ounce of Gold? The Direct Answer

One troy ounce is exactly 31.1034768 grams, usually rounded to 31.1035 g. One avoirdupois ounce is exactly 28.349523125 g, rounded to 28.3495 g. Both figures are exact by definition, not estimates.

The gap has a simple mechanism: the two systems share one atom, the grain, fixed at 64.79891 milligrams. A troy ounce is 480 grains, an avoirdupois ounce 437.5, and 480 divided by 437.5 is 1.0971. They were never converted into each other; they count a different number of the same grain.

What the Wrong Ounce Actually Costs You

Take a one-ounce bullion coin and check it against a per-gram quote. Assume an ounce is 28.35 g and you compute 28.3495 x $131.14 = $3,717.75. The coin actually holds 31.1035 g, worth 31.1035 x $131.14 = $4,079.00. You have under-valued it by $361.25.

The mirror mistake costs more, and it is the one that ends up in spreadsheets. Divide $4,079 by the wrong 28.3495 g and you get $143.88 per gram instead of $131.14. Apply that to a real troy ounce and you value it at $4,475, an overstatement of $396 on one coin and nearly $4,000 on a 10 oz bar. The live gold price per gram settles it.

1 oz Gold in Grams: Conversion and Value Table

Bullion is minted in fractions and multiples of the troy ounce, so these are the weights you meet at a counter. Values use $4,079 per ounce, or $131.14 per gram, for pure 24K metal; see live gold rates for movements.

Coins and bars trade above these pure-metal figures, scrap jewellery below. A one-ounce Krugerrand also weighs more than 31.1035 g in total, because it carries a full troy ounce of fine gold plus copper alloy. For scale, see what a gram of gold looks like.

The Troy Pound Paradox: Heavier Ounce, Lighter Pound

Here is the part most people get backwards. The troy ounce is heavier, so the assumption is that every troy unit is heavier. It is not. A troy pound is 12 troy ounces, 373.24 g; a standard pound is 16 everyday ounces, 453.59 g. The troy pound is 17.7% lighter.

In grains the reason is obvious: 5,760 in a troy pound against 7,000 in an avoirdupois pound. The 9.7% advantage per ounce is swamped by four fewer ounces in the pound. It is also why the trade never quotes gold per pound; the gold price per pound page states which pound it uses.

Which Metals Use the Troy Ounce, and Which Do Not

• Troy ounces: gold, silver, platinum, palladium and rhodium. Silver is quoted the same way, currently $58.14 per troy ounce.
• Metric carats: diamonds and gemstones, 0.2 g each, unrelated to the karat used for gold purity.
• Avoirdupois ounces and pounds: food, parcels, body weight, every non-precious good.
• Pennyweight (dwt): common with North American scrap buyers. One dwt is 1/20 of a troy ounce, or 1.55517 g, so divide a per-dwt offer by 1.55517 to compare it per gram.
• Grams and kilograms: jewellery retail across Europe, the Gulf and Asia, and wholesale bar trading.

That gives a rule you can apply in ten seconds at a counter. If a price is quoted per ounce for a precious metal, it is a troy ounce, without exception. If a kitchen, post office or gym scale says 'oz', it is not.

Where the Troy Ounce Came From

The name points to Troyes in the Champagne region of medieval France, whose fairs were among the great commercial meeting points of twelfth and thirteenth century Europe. Merchants from Italy, Flanders and England needed one weight standard they could all trust for coin and bullion.

England adopted troy weight for gold and silver in the sixteenth century, and Britain abolished it for general trade in 1879 while keeping it for precious metals. Bullion contracts, assay certificates and decades of price history are denominated in troy ounces; the LBMA fixes in them and the COMEX contract is 100 troy ounces. Switching would break every long-run price series. For the regional units alongside it, see all gold weight units explained.

Frequently Asked Questions

How many grams in an ounce of gold?

There are 31.1035 grams in an ounce of gold, because gold is measured in troy ounces. The everyday avoirdupois ounce used for food and post is 28.3495 grams, 2.754 g lighter. Gold, silver, platinum and palladium all use the troy figure.

What is a troy ounce, and how much does a troy ounce weigh?

A troy ounce is the precious-metals weight unit, equal to 480 grains or exactly 31.1034768 grams. It is one twelfth of a troy pound, not one sixteenth of a standard pound. Spot prices, futures contracts and refinery bars are all denominated in it.

Troy oz vs oz: is a troy ounce the same as a regular ounce?

No. A troy ounce is 9.71% heavier: 31.1035 g against 28.3495 g. They come from different medieval systems that share the name 'ounce'. Confusing them understates a one-ounce coin by $361 at $131.14 per gram, or overstates it by $396 if you divide by the wrong figure.

How much is an ounce of gold at today's price?

At the time of writing one troy ounce of pure gold is $4,079, or $131.14 per gram. That is fine-metal value only; a minted coin trades above it and scrap jewellery below. Spot moves continuously, so check a live quote first.

How many grams in 1 oz of gold on a kitchen scale?

A kitchen scale in 'oz' mode counts 28.3495 g per ounce, so it will not read a bullion ounce correctly. Weigh in grams and divide by 31.1035 to get troy ounces. A genuine one-ounce coin reads about 1.10 on that scale.

Why do gold markets still use troy ounces?

Because continuity is worth more than tidiness. Britain kept the troy ounce for precious metals in 1879 when it dropped it elsewhere, and bullion contracts, mint standards and price records were already built on it. The LBMA and COMEX still quote per troy ounce.

Conclusion

One number closes this question: an ounce of gold is 31.1035 grams, and every per-ounce price for a precious metal uses it. Convert to grams first, value in grams, convert back at the end, and the trap disappears. Run it through the troy ounce to grams calculator, check the current gold price per gram, and use the gold guide for the wider set of units and formulas. The pound carries the same trap in a larger size — how much is a pound of gold worth works through the troy pound versus standard pound gap, and the 100 gram gold bar shows what these conversions look like on a real product.