One carat equals to 0.2 grams or 200 milligrams. Carat weight is the prime factor that determines the weight of a diamond. Larger diamonds are undoubtedly costlier. Carat makes expressing diamond weight easier as compared to milligrams. Instead of giving three labels to diamonds weighing 20 milligrams, 211 milligrams and 220 milligrams, carat offers a category for fitting the diamonds in a one category, placing these diamonds in one-carat range.

One should not forget that high carat weight does not necessarily mean a larger looking diamond. Even diamonds of the same weight can differ on a basis of other factors, especially cut that influences perceived size. Large diamonds are rare to find and much in demand as compared to small diamonds even of the same quality. The price of a one-carat solitaire diamond ring is more than a ring with smaller diamonds making up the same carat weight. Diamond comparison is not effective until you compare the diamonds of similar features and qualities. While comparing the value of different diamonds, divide cost of every diamond in accordance with the carat weight and then calculate its price per carat.