A troy ounce (oz t) is the standard unit for weighing precious metals and equals 31.1035 grams. It is about 10% heavier than the everyday avoirdupois ounce of 28.35 grams.
How the troy ounce works
Bullion prices around the world are quoted per troy ounce, so a Singapore dealer quoting a gold coin in Singapore dollars is still working from a US dollar price per troy ounce, converted into SGD. One troy ounce is exactly 31.1034768 grams. The ounce on a kitchen scale or a food label is the avoirdupois ounce, 28.3495 grams. If you confuse the two you will underestimate the metal content by roughly 9%.
The figure that matters is the fine weight: how much pure metal the item holds. A coin marked "1 oz" always contains one troy ounce of fine metal, but its total weight can be higher if the alloy includes copper or silver.
| Coin | Gross weight | Fineness | Fine gold |
|---|---|---|---|
| 1 oz Canadian Maple Leaf | 31.10 g | 999.9 | 31.10 g (1 oz t) |
| 1 oz South African Krugerrand | 33.93 g | 916.7 | 31.10 g (1 oz t) |
Both coins hold the same gold. The Krugerrand is heavier because of the copper alloy, not because it has more value. You can compare current offers on the 1 oz Krugerrand in SGD and see how a premium changes the gap between coins with identical metal content.
Tael and tola: the older units you still meet in Singapore
Singapore's gold trade grew from Chinese, Malay and Indian merchant traditions, and two older units are still heard in gold shops in Chinatown and Little India.
- Tael (tahil). Singapore's Weights and Measures Act lists the tahil as 1 1/3 ounces, or 37.7994 grams. Many bars sold as "1 tael" in the regional market, however, weigh 37.5 grams. Always read the gram weight printed on the bar or certificate rather than relying on the name. A 37.5 g bar holds about 1.2057 troy ounces.
- Tola. Used by South Asian buyers, one tola is 11.6638 grams, so a 10 tola bar weighs 116.638 grams, or 3.75 troy ounces.
Quick conversions
| Unit | Grams | Troy ounces |
|---|---|---|
| 1 troy ounce | 31.1035 | 1.0000 |
| 1 tahil (Weights and Measures Act) | 37.7994 | 1.2153 |
| "1 tael" bar sold at 37.5 g | 37.5 | 1.2057 |
| 1 tola | 11.6638 | 0.3750 |
| 1 kilogram | 1,000 | 32.1507 |
Using the troy ounce when you compare prices
To compare a tael bar, a 50 g bar and a 1 oz coin, convert each to price per gram of fine gold. Divide the total price, including delivery or collection costs, by the fine weight in grams. Our gold price per gram in SGD gives you the benchmark, and the difference between your result and that figure is what you pay above the spot price.
For jewellery the calculation changes again: a 916 bangle quoted by weight contains only 91.6% gold, so check its fineness before converting.
Related terms
Fineness Spot Price Premium over Spot
FAQ
How many grams is 1 troy ounce of gold?
One troy ounce is 31.1035 grams, and a 1 oz bullion coin always contains that much fine gold regardless of its total weight.
How many grams is 1 tael of gold in Singapore?
The Weights and Measures Act defines the tahil as 37.7994 grams, but many tael bars sold in the region weigh 37.5 grams, so check the weight stamped on the bar.
Is a troy ounce the same as a normal ounce?
No. A troy ounce is 31.1035 grams while the normal avoirdupois ounce is 28.35 grams, so a troy ounce is about 10% heavier.