Diamonds are weighed in diamond carat weights. A carat weighs 200 milligrams. Diamond professionals also use the point system for smaller diamonds, with 100 points being equal to one carat.

A carat is usually abbreviated to ct.

Cttw refers to total carat weight. It is the total weight of all the diamonds in a piece of jewelry. For example, in the case of diamond earrings, the total carat weight refers to the weight of the diamonds in both earrings together. If the total carat weight is 1 carat, each individual earring is set with a 1/2 carat diamond.

The Connection Between Carat Weight And Price

All factors being equal, a larger diamond will cost more per carat than a smaller diamond because it is rarer. Two half carat diamonds will typically cost less together than a single one carat diamond. A four carat diamond will cost more than four times the price of a two carat diamond of the same quality.

The Connection Between Carat Weight And Dimensions

Two diamonds with exactly the same carat weight but with a different shape can have very different dimensions depending on their cut.

10.00 x 5.20 mm - One carat marquise diamond
6.30 x 6.30 mm - One carat round diamond
5.50 x 5.50 mm - One carat princess diamond
8.00 x 5.50 mm - One carat pear diamond

Carat weight is only one of the factors to consider when buying a diamond. Read more about color, cut and clarity.