Troy Ounce to Grams: Troy Weight Converter
1 troy ounce = 31.1034768 grams exactly, about 31.1 g. That is 9.7% heavier than an ordinary (avoirdupois) ounce of 28.35 g.
Troy weight converter
Source: NIST Handbook 44, Appendix C (General tables of units of measurement) · All sources
Precious metals are weighed in troy units. Convert any troy, avoirdupois or metric weight below, or use the charts for the common bullion and jewelry sizes.
Troy ounces to grams chart
Common bullion sizes: 1/10, 1/4 and 1/2 oz coins, 1 oz coins and rounds, 10 oz and 100 oz bars, and the 1 kg bar (32.15 oz t).
| Troy ounces | Grams | Avoirdupois oz | Pennyweights |
|---|---|---|---|
| 1/10 ozt | 3.11 g | 0.11 oz | 2 dwt |
| 1/4 ozt | 7.776 g | 0.274 oz | 5 dwt |
| 1/2 ozt | 15.552 g | 0.549 oz | 10 dwt |
| 1 ozt | 31.103 g | 1.097 oz | 20 dwt |
| 2 ozt | 62.207 g | 2.194 oz | 40 dwt |
| 5 ozt | 155.517 g | 5.486 oz | 100 dwt |
| 10 ozt | 311.035 g | 10.971 oz | 200 dwt |
| 12 ozt | 373.242 g | 13.166 oz | 240 dwt |
| 32.15 ozt | 1,000 g | 35.274 oz | 643.01 dwt |
| 100 ozt | 3,110.348 g | 109.714 oz | 2,000 dwt |
The troy weight system
| Unit | Equals | Metric |
|---|---|---|
| 1 grain (gr) | — | 0.06479891 g (exact) |
| 1 pennyweight (dwt) | 24 grains | 1.55517384 g |
| 1 troy ounce (ozt) | 20 pennyweights = 480 grains | 31.1034768 g |
| 1 troy pound (lb t) | 12 troy ounces = 5,760 grains | 373.2417216 g |
The grain is the one unit shared by the troy, avoirdupois and old apothecaries' systems, which is why grains still appear on ammunition, arrows and some medicines. Everything else is built from it: 480 grains to the troy ounce, 437.5 grains to the avoirdupois ounce.
Troy vs avoirdupois
troy ounces = grams ÷ 31.1034768 troy ounces = avoirdupois ounces × 0.9114583Example: a coin marked 1 oz weighs 31.1 g of fine metal, not 28.35 g. A kitchen or postal scale reads in avoirdupois ounces, so a 1 troy oz coin shows as about 1.10 oz. If you weigh a 10 oz bar on a kitchen scale, expect about 10.97 oz.
Karats and fineness
Gold purity is given in karats out of 24, or as fineness in parts per thousand. 24K is pure gold (999), 22K is 916.7, 18K is 750, 14K is 583.3 and 10K is 416.7. A 10 g ring stamped 14K contains 10 × 0.5833 = 5.83 g of gold, or 0.188 troy ounce.
Frequently asked questions
How many grams are in a troy ounce?
Exactly 31.1034768 grams. The value is fixed by the 1959 international definition of the pound (453.59237 g) and the grain (1/7,000 pound).
Is a troy ounce heavier than a regular ounce?
Yes. A troy ounce is 480 grains (31.10 g); a regular avoirdupois ounce is 437.5 grains (28.35 g). So 1 troy ounce = 1.0971 ordinary ounces.
Is a troy pound heavier than a regular pound?
No, the opposite. A troy pound has only 12 troy ounces (373.24 g), while an avoirdupois pound has 16 smaller ounces (453.59 g). Troy pounds are rarely used today.
How many troy ounces are in a kilogram?
32.1507 troy ounces. That is why a 1 kg gold bar is often listed as 32.15 oz t.
What is a pennyweight?
A pennyweight (dwt) is 1/20 of a troy ounce: 24 grains or 1.555 g. Jewelers in the US still price scrap gold and casting metal by the pennyweight.
Why is gold weighed in troy ounces?
Troy weight was the standard for precious metals in medieval Europe (the name is usually traced to the market town of Troyes, France). The London and New York bullion markets kept it, so gold, silver, platinum and palladium prices are still quoted per troy ounce.
Sources
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- Last updated
- November 5, 2026
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