Carat (purity)

For other meanings, see Carat.

The carat is a measure of the purity of precious metals and their alloys, such as gold. One carat in this sense is one-twenty-fourth purity by weight. Therefore 24 carat gold is pure gold, 12 carat gold is 50% purity, etc. In the United States and Canada, the spelling karat is usually used for the measure of purity, while carat refers to the measure of mass.