A carat is the unit of weight by which a diamond is measured. The carat-weight of a diamond is the easiest measurement of the 4C’s to determine. Carat-weight is not a factor which denotes the quality of a diamond, but merely its size by weight.

The word "carat" derives from the carob seeds that people used in ancient times to balance scales. So uniform in shape and weight are these little seeds that even today's sophisticated instruments cannot detect more than three one-thousandths of a difference between them.

"Carat” is not to be confused with "karat," which is used to indicate the purity of gold. One carat is subdivided into 100 "points". Therefore a diamond measuring 75 points is 3/4 carat in weight, or 0.75ct. There are five carats in a gram.