Karats, fineness and purity

Purity is expressed either in karats or in fineness. Pure gold is 24 karat, or 999.9 parts per thousand.

An 18K item is 75% gold; 14K is about 58.3%; 22K, common in some bullion coins, is about 91.67%. Fineness simply writes these as decimals such as .750 or .9167.

U.S. rules require karat markings to be accurate within tight tolerances, and reputable refiners stamp fineness and weight on every bar.

The value of any gold item is its pure gold content times the spot price, before premiums. Knowing purity is the first step in fair pricing.