Gold is weighed differently around the world
A gram is a gram everywhere, but almost no gold market quotes in grams alone. London and New York trade in troy ounces of 31.1034768 grams — a unit that has nothing to do with the ordinary ounce used for food, which is 28.35 grams and about 10% lighter. Mixing the two is a costly mistake.
Across South Asia the unit is the tola, 11.6638 grams, defined as exactly three eighths of a troy ounce. Bangladesh calls the same weight a vori. Because it is tied to the troy ounce rather than a round metric figure, ten tola is 116.638 grams rather than a tidy 116, and rounding early is where errors creep in.
The tael problem
The tael is where most conversion errors happen, because the same word means different weights in neighbouring markets.
| Tael | Grams | Used for |
|---|---|---|
| Hong Kong (bullion) | 37.429 | Exactly 1.2 troy ounces. The CGSE standard for licensed bullion trading |
| Hong Kong (trade) | 37.7994 | Jewellery and general commerce |
| Taiwan | 37.5 | Local market |
| Mainland China (市兩) | 50 | Metric-aligned, half of a jin |
The Hong Kong bullion tael was fixed at 1.2 troy ounces by the colonial Weights and Measures Ordinance of 1885 and remains the standard used by licensed members of the Chinese Gold and Silver Exchange Society. A quote in "taels" is ambiguous unless you know which one — the gap between 37.429 and 50 grams is a third of the value.
Thailand quotes two baht weights
Thai gold is quoted in baht, and the weight depends on the form. One baht of bullion is 15.244 grams; one baht of ornamental jewellery is 15.16 grams. Both trade at the Thai market standard of 96.5% fineness, roughly 23.16 karat, which sits between the 22K common in India and the 24K sold as investment metal elsewhere.
Vietnam uses the lượng (also written cây or tael) of 37.5 grams, divided into ten chỉ of 3.75 grams. Korea uses the don, also 3.75 grams — the two systems share a root, which is why the small units match exactly.
Purity is written differently too
Karat and millesimal fineness describe the same thing from different directions. 24K is pure, and each karat below that is one twenty-fourth less gold.
- 24K / 999 — investment bars and coins. Too soft for most jewellery
- 22K / 916 — the jewellery standard across India and much of the Middle East
- 21K — common in Gulf markets
- 18K / 750 — the usual choice in Europe and for branded jewellery
- 14K / 585 and 10K / 417 — widespread in the United States
- 9K / 375 — the lowest grade that may legally be called gold in the UK
The UK operates the oldest continuous hallmarking system in the world, running since 1300, and most EU states follow the Vienna Convention marks of 375, 585, 750 and 916. Where you see a three-digit stamp, it is parts per thousand.
Why buying and selling are so far apart
Gold can hold its value exactly and still lose you money on a round trip, because charges land on both ends. Buying adds a making charge or premium — small on bars, often 10–25% on worked jewellery — and then any VAT or sales tax on top. Selling subtracts refining costs and the dealer's margin, and tax paid on purchase is generally not refunded.
Put together, the spread between what a dealer sells at and buys back at commonly runs 15–20%, and wider for intricate jewellery. That is the amount the metal price has to rise before you break even. This calculator shows that break-even figure directly, so you can see what you are actually committing to.
Where the numbers come from
- Spot reference price — the international market price that moves through the trading day. All calculations use this. It is a market reference, not an official benchmark fix, and the provider does not disclose its upstream source.
- Exchange rates — market rates refreshed once a day, cross-checked against a rate computed from the European Central Bank's euro reference rates. The ECB quotes against the euro only, so USD/KRW and similar pairs are cross-rates, not ECB-published figures.
Every figure on this page is converted from the international benchmark. It is not a retail quote. Your local shop price includes duties, taxes and margins that vary by country and by dealer. Use the local premium field to model that gap, or simply enter your dealer's quoted price and work from there.
Conversions used here
- troy ounce 31.1034768 g · tola / vori 11.6638038 g · Thai baht 15.244 g (bullion) or 15.16 g (jewellery)
- Hong Kong bullion tael 37.429 g · Taiwan tael 37.5 g · Chinese 市兩 50 g · lượng 37.5 g · chỉ 3.75 g · don 3.75 g
- Buying = spot × purity × weight × (1 + premium) × (1 + making charge) × (1 + tax)
- Selling = spot × purity × weight × (1 + premium) × (1 − buyback deduction)
Information only, not investment advice. For everyday unit conversion see the other calculators.