How Many Grams in a Troy Ounce? The Short Answer
One troy ounce = 31.1035 grams. Gold, silver, platinum, and palladium are weighed in troy ounces, not the regular (avoirdupois) ounces used for groceries and body weight — a regular ounce is only 28.3495 grams. So if you are asking how many grams in an ounce of gold, the answer is 31.1035 g, and every gold coin and bar size converts from that one number: a 1/10 oz coin holds 3.11 g of gold, a 1/4 oz holds 7.78 g, a 1/2 oz holds 15.55 g, and a full 1 oz coin or bar holds 31.10 g. The complete chart, including diameters, is below.
Gold coin sizes are quoted in troy ounces, but most people think in grams — and that mismatch causes real confusion at buying time. Here is the complete conversion in one place: a 1/10 oz gold coin contains 3.11 grams of gold, a 1/4 oz coin contains 7.78 grams, a 1/2 oz coin contains 15.55 grams, and a full 1 oz coin contains 31.10 grams. This chart covers every common fractional size with its weight in grams and its diameter, so you can compare sizes side by side before you buy.
Weights below are the fine (pure gold) content stated by the issuing mints, converted at 1 troy ounce = 31.1035 grams. Diameters shown are the official specifications for American Gold Eagle coins; other mints’ coins of the same weight class are within a millimeter or two.
Gold Coin Sizes in Grams: The Full Chart
| Coin size | Gold content (grams) | Gold content (grains) | Diameter (Gold Eagle) |
|---|---|---|---|
| 1/20 oz | 1.56 g | 24.0 | — |
| 1/10 oz | 3.11 g | 48.0 | 16.5 mm |
| 1/4 oz | 7.78 g | 120.0 | 22.0 mm |
| 1/2 oz | 15.55 g | 240.0 | 27.0 mm |
| 1 oz | 31.10 g | 480.0 | 32.7 mm |
| 2 oz | 62.21 g | 960.0 | varies by mint |
| 5 oz | 155.52 g | 2,400.0 | varies by mint |
| 10 oz | 311.03 g | 4,800.0 | varies by mint |
| 1 kilogram | 1,000 g (32.15 troy oz) | 15,432.4 | varies by mint |
For a deeper look at the smallest common size, see our guide to how much a 1/10 oz gold coin weighs in grams, and for bars, our 1 gram gold bar dimensions guide.
Why the Scale Weight Is Higher Than the Gold Content
Put a 1 oz American Gold Eagle on a scale and it will read about 33.93 grams, not 31.10. That is not a mistake. Gold Eagles are struck in 22-karat gold — the full troy ounce of pure gold is alloyed with silver and copper for hardness, so the finished coin weighs more than its gold content. The gross weights of the Gold Eagle family are 3.39 g (1/10 oz), 8.48 g (1/4 oz), 16.97 g (1/2 oz), and 33.93 g (1 oz). Pure .999 or .9999 fine coins, such as Canadian Maple Leafs, weigh almost exactly their stated content. When you weigh a coin to verify it, always compare against that specific coin’s published gross weight, not the conversion chart alone.
How Big Is Each Size, Really?
Diameters surprise first-time buyers. A 1/10 oz gold coin at 16.5 mm is smaller than a U.S. dime (17.9 mm) — a lot of gold value in a very small disc, which is exactly why fractional gold is popular for flexible budgets and gifts. A 1/4 oz coin (22 mm) sits between a dime and a nickel in feel. A 1 oz gold coin (32.7 mm) is a little wider than a U.S. half dollar. For silver, the same troy weights apply — a 1 oz silver coin contains 31.10 g of silver — but because silver is less dense, the coin is larger: a 1 oz American Silver Eagle is 40.6 mm across.
Which Size Should You Buy?
There is no wrong size, only a wrong fit. Smaller fractions carry higher premiums per gram but let you buy in smaller steps and sell in smaller pieces later. Full 1 oz coins carry the lowest cost per gram and the deepest resale market. Many stackers hold a mix: 1 oz coins as the core, fractional pieces for flexibility. If you are deciding between neighboring sizes, our related guides on silver coin melt value and bar sizes can help you compare formats before you commit.
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FAQ
How many grams are in a 1/10 oz gold coin?
A 1/10 oz gold coin contains 3.11 grams of pure gold (one tenth of 31.1035 g). A 22-karat coin like the Gold Eagle weighs 3.39 g in total because of its alloy metals.
Is a troy ounce the same as a regular ounce?
No. A troy ounce is 31.1035 grams; a regular (avoirdupois) ounce is 28.35 grams. Precious metals are always weighed in troy ounces, which is why a “1 oz” gold coin weighs more than an ounce of almost anything else in your kitchen.
What is the most popular gold coin size?
The 1 oz size is the market standard — lowest premium per gram and the easiest to resell. The 1/10 oz is the most popular fractional size for smaller budgets.
Do silver coins use the same sizes?
Yes — silver coins and bars are also sold in troy weights (1/10 oz, 1/4 oz, 1/2 oz, 1 oz, and larger), with the same gram conversions. The coins are physically bigger because silver is less dense than gold.
Educational content only — not financial advice. Coin specifications are as published by the issuing mints; always verify the exact specification of a specific coin before relying on a weight or measurement.