A carat is a unit of measurement, it's the unit used to weigh a diamond. One carat is equal to 200 milligrams, or 0.2 grams. The word carat was based on the Carob tree (Ceratonia siliqua) seed which was use as a standard of measurement by the Arabs.Carob seeds were used as weights on precision scales because of their uniform size.
In 1907 the metric carat of 200 milligrams was adopted, which is now universally used today.A carat can also be further divided into "points". There are 100 points to a carat.
1 carat = 200 milligrams
[NOTE: Don't confuse "carat weight" with "karat," the method of determining the purity of gold.]