- 1 troy ounce = 31.1034768 grams; 1 kilogram = 32.1507 troy ounces.
- A troy ounce is ~10% heavier than the avoirdupois ounce (28.3495 g) and is the global standard for precious-metal quotes.
- Price per gram = price per ounce ÷ 31.1035 — the conversion used across our price pages.
Live conversion of the indicative XAU/USD price (Gold API). Other currencies — in prices by currency.
Factors worth memorising
- 1 troy ounce = 31.1034768 g;
- 1 kilogram = 32.1507 troy ounces;
- price per gram = price per ounce ÷ 31.1035;
- 1 tonne (central-bank and mining data) = 32,150.7 oz.
Who uses which units
Exchanges and the professional market quote gold in US dollars per troy ounce. Retail in continental Europe, the CIS and Asia works in grams; India also uses the tola (11.664 g), and the Shanghai Gold Exchange quotes yuan per gram. Reserve and mining statistics are published in tonnes.
Quick conversions for a task
To value an item or bar it is easier to start from the per-gram price of the right fineness: formulas and the table are in the purity guide; automatic calculation with a currency picker — in the gold calculator.
Frequently asked questions
How many grams are in a troy ounce?
Exactly 31.1034768 grams. It is the international standard for precious metals: gold, silver, platinum and palladium are quoted in troy ounces on every major venue.
How does a troy ounce differ from a regular ounce?
The avoirdupois ounce is 28.3495 g; the troy ounce is 31.1035 g — about 10% heavier. The name comes from Troyes, a medieval French fair town whose weight system stuck to precious metals.
Why isn't gold quoted per gram directly?
Exchange standards (COMEX, LBMA) are built on troy ounces: a COMEX contract is 100 oz, a London Good Delivery bar about 400 oz. Retail markets convert the quote to grams — the conversion we show on our price pages.
More guides
Updated: 2026-07-19. This material is informational and not investment advice — see the disclaimer. Data provenance is described in the methodology.