The unit of measurement of a diamond
is called carat weight or carat in short. 1 carat (ct) is equal to 200 milligrams (mg) in weight wherein each cart is divided into 100 points. Similar to currency, a 0.50 ct. is equal to 50 points and a 0.25 ct. is equal to 25 points.
A related term, Total Carat Weight (TCW), this is the total carat weight of several pieces of diamonds. For example, a diamond engagement ring
with a center stone of 1.00 ct., side stones of 0.50 ct. and accents stones of 0.32 has a Total Carat Weight of 1.82 TCW.