What is a troy ounce?

If you have ever weighed a gold coin on a kitchen scale and thought it was too heavy, or wondered why a "pound" of gold is lighter than a pound of butter, the troy ounce is the reason. This guide gives the exact figure, where it came from, and how to convert it to any unit a dealer might use.

How many grams are in a troy ounce, exactly?

One troy ounce is exactly 31.1034768 grams. The figure is exact because of how it is built. The troy ounce is defined as 480 grains, and since the international yard and pound agreement took effect in 1959, the grain has been fixed at exactly 64.79891 milligrams. The US National Institute of Standards and Technology (NIST) prints that grain value in bold in its guide to conversion factors, its sign that a factor is exact. Multiply 480 by 64.79891 mg and you get 31,103.4768 mg.

What is the difference between a troy ounce and a regular ounce?

The ounce on food packets and kitchen scales is the avoirdupois ounce (from old French for "goods of weight"). It is 437.5 grains, or 28.349523125 g. The troy ounce is 480 grains. Both systems share the same grain, which is why the comparison is exact: a troy ounce is 480/437.5, or 1.0971 times, an ordinary ounce.

The pounds work the other way round. A troy pound has 12 troy ounces, while an avoirdupois pound has 16 ordinary ounces. So a troy pound (373.24 g) is lighter than an everyday pound (453.59 g). That gives the old riddle its answer: a pound of feathers weighs more than a pound of gold, if the gold is weighed in troy pounds.

Grams derived from NIST's exact grain of 64.79891 mg. The avoirdupois pound is defined as exactly 0.45359237 kg.

Where does the troy ounce come from?

The name is generally thought to come from Troyes, a market town in the Champagne region of France where merchants from across Europe traded at the great medieval fairs. Another theory links it to the "tron", a type of balance. Either way, troy weights were in use in England by the 15th century, and in 1527 they were made the official standard for gold and silver.

The British later abolished the troy pound, but kept the troy ounce for precious metals. It survives in UK law today: the Weights and Measures Act 1985 bans the "ounce troy" from use in trade "except for the purposes of transactions in, or in articles made from, gold, silver or other precious metals". Across the Atlantic, the US Congress adopted the British troy pound as the standard for American coinage on 19 May 1828. In the US today, NIST's model regulation says precious metals must be sold by "either troy weight or SI units" (NIST).

Why is gold still priced in troy ounces?

Because the market's reference price is. The LBMA Gold Price, set twice each London business day and used as the benchmark by refiners, banks and central banks, is quoted in US dollars per troy ounce (LBMA). Futures on New York's COMEX exchange trade in troy ounces too. Every dealer and mint, from the US to Australia, starts from those prices, so the coins and bars they sell are made in troy-ounce sizes: 1 oz, 1/2 oz, 1/4 oz and 1/10 oz.

Gram and kilo bars sit alongside them, particularly in Europe and Asia, and jewellery is sold by the gram almost everywhere. That is why you will often need to convert. To see how the per-ounce price becomes a live quote, read what the gold spot price is.

How do you convert troy ounces to grams, kilos and other units?

A tola is 3/8 of a troy ounce (about 11.6638 g), a unit widely used for gold in South Asia and the Gulf. A 10 tola bar holds 3.75 troy ounces.

Quick rules of thumb: grams to troy ounces, divide by 31.1035; troy ounces to grams, multiply by 31.1035; kitchen-scale ounces to troy ounces, multiply by 0.9115.

Troy ounce converter

The gold value uses the live spot price and the purity you choose; it is a melt value, not a dealer price. A dedicated troy ounce converter page is also available.

What is one troy ounce of gold worth today?

Spot-based values, Loading. Spot is the wholesale price; you pay more when you buy and receive less when you sell.

Worked example: what one troy ounce actually cost in four countries

Spot is per troy ounce, but nobody sells gold at spot. The table uses real single-coin and single-bar prices from GoldVetted's automated price checks on 10 and 11 October 2026 (a weekend, when the market was closed and prices were static), and turns each into a price per gram of gold.

GoldVetted price checks: US and UK on 10 October 2026 (see the premium tracker), Canada and Australia on 11 October 2026. Premium = price divided by spot, minus one. Cost per gram = price divided by 31.1035, because each product holds one troy ounce of gold.

Every one of those products holds the same 31.1035 g of gold, even though the Eagle weighs 33.931 g in the hand. That is the key point for buyers: compare what you pay per troy ounce (or gram) of fine gold, not per coin weight. Country guides walk through dealers and taxes: where to buy gold in the US, in the UK, in Canada and in Australia.

Which coins and bars contain one troy ounce of gold?

All of the major 1 oz bullion coins contain one troy ounce of fine gold. Their total (gross) weight differs, depending on whether the gold is alloyed.

Weights from the Royal Canadian Mint, Perth Mint, Royal Mint and US Mint product pages; Krugerrand weight from its published specifications.

The 22 carat coins weigh about 2.8 g more because copper and silver are added on top of the full ounce of gold, making them harder wearing. They are not "short" on gold. Our guide to gold coins vs gold bars covers which suits which buyer.

What mistakes do people make with troy ounces?

• Using a kitchen scale in ordinary ounces. A 1 oz Maple Leaf reads about 1.097 oz on a food scale. Weigh in grams instead.
• Dividing the ounce price by 28.35. That overstates the per-gram value by about 9.7%. Divide by 31.1035.
• Thinking a heavier coin holds more gold. An Eagle or Krugerrand weighs 33.93 g but holds exactly one troy ounce of gold, the same as a 31.1 g Maple Leaf.
• Valuing jewellery at the full ounce price. 18ct is 75% gold and 9ct is 37.5%, so multiply by purity first.
• Mixing up pennyweights and grams. Some jewellers and scrap buyers quote per pennyweight, which is 1.555 g. A price per dwt looks about 55% higher than the same price per gram.

How does the troy ounce work in the US, UK, Canada and Australia?

Whatever country you buy in, the steps are the same: work out how many troy ounces of fine gold you are getting, multiply by spot, and compare that with the price. Our guide on how to buy gold takes you through the rest, from choosing a dealer to storage.

This guide is information, not financial advice. Gold prices can fall as well as rise.

Not financial advice. GoldVetted provides general information to help you compare options. It is not personal financial, tax or legal advice. Gold prices go down as well as up, and you may get back less than you pay. Check tax rules with the official source or a qualified adviser before you act.