How this calculator works
The calculator starts from the live 24K gold price per troy ounce, converted to JPY at the current exchange rate. Your weight is converted to grams (1 troy ounce = 31.1034768 g, 1 tola = 11.6638038 g), and the value is adjusted for purity — the multiplier is simply the karat divided by 24, so 22K/916 gold uses 22 ÷ 24 ≈ 0.9167. The formula: value = grams × pure gram price × purity, plus any premium and minus any discount you enter.
Japanese jewellery is typically K18 (75% gold), with pure K24 reserved for investment items and ceremonial pieces. Purity is stamped as K18 or K24 together with the maker's mark, and major retailers publish a daily gold price in yen per gram.