Each of the twenty-four equal divisions of the ounce. In jewelry, the number of carats expresses the number of parts of fine gold contained in twenty-four parts of alloy. Today the unit is designated by the letter K. By extension, the carat has become the unit of weight for precious stones and pearls. The carat is subdivided into four grains, in turn divided into quarters and sixteenths. The metric carat, instead, is equal to 200 milligrams.