Gold price per gram by karat

Karat measures parts of gold out of twenty four. 18k is 18 parts gold and 6 parts alloy, which is 75% pure. 14k is 58.3%, 10k is 41.7%. The value per gram is simply the fine gold price multiplied by that fraction, which is why the table below is a straight line rather than anything mysterious.

The trade rounds some of these. 22k is treated as 91.67% and 24k as 99.9% rather than a theoretical 100%, because absolutely pure gold is too soft to work.

European and most modern pieces carry a three digit fineness: 375 for 9k, 417 for 10k, 585 for 14k, 750 for 18k, 916 for 22k, 999 for 24k. US pieces more often use 10K, 14K, 18K directly.

A missing stamp does not mean the piece is fake. Older jewellery, and anything that has been resized, often lost its hallmark. Any buyer will test rather than trust the stamp anyway.

22k and 24k carry more gold per gram and are worth more, but they are soft, scratch easily and are rare in western jewellery. 14k dominates the US market precisely because it survives daily wear. When selling, karat determines the price per gram and nothing else. There is no premium for being harder or more common.