- For other uses of the word carat, see Carat.
The carat is a unit of mass used for gems, and equals 200 milligrams. The word derives from the Greek keration (fruit of the carob), via Arabic and Italian. Carob seeds were used as weights on precision scales because of their uniform size. In the past, different countries each had their own carat, roughly equivalent to a carob seed. However, in 1907 the metric carat of 200 milligrams was adopted, which is now universally used today.