The gold weight conversion procedures of the London Bullion Market Association (LBMA) are used for trading on the London bullion market and accepted internationally.
The LBMA records its basis for converting the weight of gold bars from grams (metric) to ounces troy (imperial), and vice versa, as follows:
1 gram = 0.0321 ounces troy
5 gram = 0.1608 ounces troy
10 gram = 0.3215 ounces troy
20 gram = 0.6430 ounces troy
½ ounce troy = 15.5517 grams
1 ounce troy = 31.1034 grams
1 kilogram = 32.1507 ounces troy
1 tonne = 32,150.70 ounces troy