Gold, silver, platinum and palladium are weighed in troy units, a system that predates the metric system by centuries and survives because the entire bullion market still prices metal per troy ounce. If you are checking a coin’s weight, valuing scrap jewelry or comparing a bar sold in grams with a spot price quoted in ounces, you need to convert between troy and metric units, and avoid confusing the troy ounce with the ordinary one on your kitchen scale.
How to use the troy weight converter
- Enter the weight in Value.
- Choose the unit you have in From: troy ounce (oz t), pennyweight (dwt), grain, troy pound, gram, kilogram, tola or carat.
- Choose the unit you want in To.
- The tape also splits the result into troy ounces and pennyweights, and into troy pounds and ounces. The table lists every unit, including ordinary ounces and pounds for comparison.
Troy weight formula
The troy system is built on the grain, which is shared with the everyday avoirdupois system and defined as exactly 64.79891 mg:
That makes a troy ounce 480 grains, or 31.1034768 g exactly, and a troy pound 5,760 grains, or 373.2417216 g. To convert, multiply by the grams per unit you start with and divide by the grams per unit you want:
Worked example: a 100-gram gold bar
Many refiners sell 100 g bars. To compare one with a spot price per troy ounce:
100 g ÷ 31.1034768 g/oz t = 3.2151 troy ounces
If gold trades at $2,400 per troy ounce, the metal content is worth 3.2151 × $2,400 ≈ $7,716, before dealer premiums.
A second example from the jewelry counter: a ring weighing 8.5 g is 8.5 ÷ 1.55517384 = 5.47 dwt.
Troy and metric conversion table
| Troy unit | Grains | Grams | Troy ounces |
|---|---|---|---|
| 1 grain | 1 | 0.06479891 | 0.00208333 |
| 1 pennyweight | 24 | 1.55517384 | 0.05 |
| 1 tola | 180 | 11.6638038 | 0.375 |
| 1 troy ounce | 480 | 31.1034768 | 1 |
| 1 troy pound | 5,760 | 373.2417216 | 12 |
| 1 kilogram | 15,432.36 | 1,000 | 32.1507466 |
| 400 oz t (London Good Delivery gold bar, nominal) | 192,000 | 12,441.39 | 400 |
Troy ounces versus ordinary ounces
The two ounce sizes differ by almost 10%, which is enough to make a costly mistake. A kitchen or postal scale reports avoirdupois ounces of 28.35 g. Weigh a one-ounce silver coin on it and you will read about 1.097 oz, not 1.000. Always convert through grams or use a scale set to troy ounces or pennyweights.
The pounds differ in the opposite direction. A troy pound is smaller than a regular pound because it contains only 12 ounces, so the heavier troy ounce paired with the lighter troy pound is a classic trivia question. In practice, the troy pound is almost never used today; bullion is traded in troy ounces, grams and kilograms.
Where troy units are used
- Bullion and coins. Spot prices for gold, silver, platinum and palladium are quoted per troy ounce, and coins such as the American Eagle are struck in fractions of a troy ounce.
- Jewelry and scrap. US jewelers and refiners commonly weigh in pennyweights; buyers in many other countries use grams.
- South Asia and the Gulf. The tola, fixed at 180 grains, is the traditional gold unit; the popular 10-tola bar weighs 3.75 troy ounces.
- Pharmacy history. The apothecaries’ system once used the same grain and ounce, which is why old prescriptions list doses in grains.
Remember that weight is only half of valuation. Multiply the troy weight by the metal’s purity (for example 0.750 for 18-karat gold) to get the fine metal content. For everyday weights, use the weight converter, or the avoirdupois weight converter for drams, stone and hundredweights.
Frequently asked questions
Is a troy ounce heavier than a regular ounce?
Yes. A troy ounce is 31.1034768 g, while an ordinary (avoirdupois) ounce is 28.349523125 g, so a troy ounce is about 9.7% heavier. Gold and silver prices are always quoted per troy ounce.
How many troy ounces are in a kilogram?
About 32.15 troy ounces. A 1 kg gold bar therefore contains 32.1507 troy ounces of metal, before allowing for its purity.
What is a pennyweight?
A pennyweight (dwt) is 24 grains, or exactly 1.55517384 grams. Twenty pennyweights make one troy ounce. Jewelers and scrap buyers in the US often weigh gold in pennyweights.
Why is a troy pound lighter than a regular pound?
A troy pound has only 12 troy ounces (5,760 grains), while an avoirdupois pound has 16 smaller ounces (7,000 grains). The troy pound weighs 373.24 g, about 82% of an ordinary 453.59 g pound.
Is a carat the same as a karat?
No. A carat (ct) is a unit of mass for gemstones equal to exactly 200 mg. A karat (k or kt) describes gold purity in 24ths, so 18-karat gold is 18/24, or 75%, pure.