A Basic Guide to Diamond Carat Weight

The carat, usually abbreviated to CT, is a unit of mass equal to 200 mg used to measure gemstones and pearls. Carat weight is one of the 4Cs of Diamond Quality – a universal method created by the GIA to evaluate diamond quality.

Basically, diamond carat weight measures how much a diamond weighs. Each carat can be subdivided into 100 “points”, which allows precise measurements to the hundredth decimal place. Stones greater than 1 carat are described in carats and decimals. A 1-carat diamond is comprised of 100 points; therefore, a 50-point diamond weighs 0.50 carats, and a diamond which weighs 0.25 carats can be described as a 25-pointer. The majority of diamonds used in fine jewelry weigh one carat or less.

 In jewelry pieces with more than one diamond, the carats are described in terms of total carat weight; i.e., the combined total weight of all the stones in the piece.

 While it is important that a diamond's value is determined using all of the 4Cs, all else being equal (clarity, color and cut), diamond price increases with diamond carat weight. This, according to the GIA, stems from two reasons: the relative rarity of larger diamonds, and the greater desirability of larger diamonds. A single 2-carat diamond will cost much more than two 1-carat diamonds, but it is also important to remember that very large diamonds with good color and clarity are very rare.

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