1 Ounce of Gold in Grams: 31.1035 g, With Conversion Tables
One ounce of gold is 31.1034768 grams, because gold is weighed in troy ounces, not the 28.35 gram ounce used for food. For most purposes 31.1035 g or 31.1 g is close enough. To convert, multiply ounces by 31.1034768; to go back, divide grams by the same number. A 1 kg bar is 32.1507 troy ounces.
The sections below give ready-made tables for coin and bar sizes, explain where the number comes from, and show how purity and price per gram fit in. For the physical side of the metal, see gold vs copper differences.
Key takeaways
- One troy ounce of gold is 31.1034768 grams; round it to 31.1035 g for everyday use.
- The kitchen (avoirdupois) ounce is 28.35 g, so using it for gold understates the weight by about 8.9%.
- A 1/10 oz coin holds 3.1103 g, a 1/4 oz coin 7.7759 g and a 1 kg bar 32.1507 troy ounces.
- Weight and gold content differ: 10 g of 22 karat gold contains 9.1667 g of pure gold.
- Price per gram = price per troy ounce divided by 31.1034768.
Table of contents
How Many Grams Are in One Ounce of Gold
The answer is 31.1034768 grams. NIST lists the troy ounce at 31.10348 g in its conversion table, and the exact value follows from the definition: a troy ounce is 480 grains, and the grain is 64.79891 milligrams. Multiply the two and you get 31.1034768 g.
Dealers, mints and market quotes all use this unit. When a coin is sold as “1 oz”, it means one troy ounce unless the seller says otherwise.
Gold Ounce to Grams Conversion Table
Coins and small bars come in fractional sizes. Each row below is the troy ounce figure multiplied by 31.1034768 and rounded to four decimal places.
| Size | Troy ounces | Grams |
|---|---|---|
| 1/20 oz | 0.05 | 1.5552 g |
| 1/10 oz | 0.1 | 3.1103 g |
| 1/4 oz | 0.25 | 7.7759 g |
| 1/2 oz | 0.5 | 15.5517 g |
| 1 oz | 1 | 31.1035 g |
| 2 oz | 2 | 62.2070 g |
| 5 oz | 5 | 155.5174 g |
| 10 oz | 10 | 311.0348 g |
| 1 kg bar | 32.1507 | 1,000 g |
| 100 oz | 100 | 3,110.3477 g |
| Good Delivery bar (approx.) | about 400 | about 12,441 g |
The last row is the large bar held in the London market. LBMA describes a Good Delivery gold bar as approximately 400 troy ounces, so its gram figure is approximate too; each bar is stamped with its own fine weight.
Grams to Troy Ounces
Jewellery and many bars in the Gulf and Asia are sold by the gram. To compare a gram price with an ounce quote, divide the grams by 31.1034768.
| Grams | Troy ounces |
|---|---|
| 1 g | 0.0322 |
| 2.5 g | 0.0804 |
| 5 g | 0.1608 |
| 10 g | 0.3215 |
| 20 g | 0.6430 |
| 50 g | 1.6075 |
| 100 g | 3.2151 |
| 250 g | 8.0377 |
| 500 g | 16.0754 |
| 1,000 g | 32.1507 |
A 100 g bar is therefore a little over 3.2 troy ounces, and a 1 kg bar just over 32.
Why Gold Uses the Troy Ounce
Two different ounces are in common use. The avoirdupois ounce, used for groceries and postage, is 28.35 g (28.34952 g in the NIST table). The troy ounce is 31.1035 g. Precious metals are still weighed in troy units.
The gap is large enough to matter. A troy ounce is 1.0971 avoirdupois ounces, so the troy unit is about 9.7% heavier; put the other way, an avoirdupois ounce is about 8.9% lighter. Weigh a 1 oz coin on a kitchen scale set to ounces and it reads about 1.1 oz. Nothing is wrong with the coin; the scale uses the other unit.
The same split applies to pounds. A troy pound is 12 troy ounces (373.24 g), while an avoirdupois pound is 16 ounces (453.59 g), so the troy pound is the lighter of the two even though its ounce is heavier.
Gross Weight and Fine Gold Content
Weight tells you how heavy an item is. It does not tell you how much gold it contains. Purity is given in karats (parts per 24) or as fineness (parts per 1,000). Fine gold content equals gross weight times purity.
| Purity | Gold share | Pure gold in 10 g |
|---|---|---|
| 24 karat | 24/24 | 10.0000 g |
| 22 karat | 22/24 | 9.1667 g |
| 18 karat | 18/24 | 7.5000 g |
| 14 karat | 14/24 | 5.8333 g |
This is why two coins both described as “1 oz” can hold different amounts of gold. A coin sold as containing one fine troy ounce has 31.1035 g of pure gold whatever it weighs in total. A 22 karat coin designed that way has to weigh about 33.93 g gross, because the alloy metal adds weight.
Check the product description for the words “fine” or “gold content”. A weight with no purity attached is not enough to value an item.
Turning a Price per Ounce Into a Price per Gram
Gold is quoted in US dollars per troy ounce, including the XAU/USD rate shown on trading platforms. To express that as a gram price, divide by 31.1034768. To get a kilogram price, multiply the ounce price by 32.1507.
Using a round illustrative figure of 3,000 USD per ounce (not a current quote): 3,000 divided by 31.1034768 is 96.45 USD per gram, and 3,000 times 32.1507 is 96,452 USD per kilogram. A retail gram price will sit above that figure, because it adds the dealer premium and, for jewellery, making charges.
If you follow gold on a chart, the move in dollars per ounce converts the same way. Our guide to analysing gold (XAU/USD) covers what drives that quote, and the gold-silver ratio compares it with silver in the same unit.
Conversion Mistakes That Change the Answer
- Using 28.35 g. That is the food ounce. On 10 ounces it understates the weight by more than 27 g.
- Rounding too early. 31.1 g is fine for one coin. On a 400 oz bar the difference from 31.1034768 g is about 1.4 g.
- Treating gross weight as gold content. Apply the karat or fineness before comparing prices.
- Mixing up fluid ounces. A fluid ounce measures volume, not mass, and has nothing to do with gold weight.
Trading gold through a broker is a separate matter from owning it; gold trading costs at a broker explains spreads and swaps on XAU/USD.
Frequently Asked Questions
How many grams are in 1 ounce of gold?
One troy ounce, the unit used for gold, is 31.1034768 grams. Rounded, that is 31.1 grams. The 28.35 gram figure belongs to the ordinary avoirdupois ounce and is not used for precious metals.
Is a gold ounce the same as a regular ounce?
No. Gold is weighed in troy ounces of 31.1035 grams, while the everyday avoirdupois ounce is 28.3495 grams. A troy ounce is about 9.7 percent heavier.
How many troy ounces are in a kilogram of gold?
A kilogram is 32.1507 troy ounces, found by dividing 1,000 grams by 31.1034768.
How much pure gold is in a 1 ounce coin?
It depends on the purity. A coin sold as containing one fine troy ounce holds 31.1035 grams of pure gold whatever its gross weight; a coin that weighs one troy ounce at 22 karat holds 22 parts in 24, which is 28.5115 grams.
Sources checked 23 September 2026. NIST, Special Publication 811, Appendix B.9 Factors for units listed by kind of quantity or field of science (mass) · LBMA, About Good Delivery.
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