Diamond weight is measured in carats. Carat is a unit that determines the weight of a diamond, not the size. High-carat diamonds are quite rare and therefore valuable. One carat equals 0.2 grams or 200 milligrams. A carat is divided into 100 points. For example, a diamond of 0.25 carat can also be called a 25-point diamond. The total carat weight (ct. tw.) determines the total weight of all the diamonds featured in a jewelry piece. So, if a ring has 5 diamonds each weighing 0.25 carats, then the total carat weight of the ring is 1.25 carats, or you could say that your ring holds 1.25 ct. tw. of diamonds. To choose the perfect carat weight of a diamond, consider the ring size, desired style, the size of your setting, and your budget.