Although commonly thought to refer to the actual size of a diamond, a carat is actually a standard unit of measure that measures the weight of a diamond. One carat is equivalent to 200 milligrams. Carat sizes are also expressed as “points”, with a carat diamond equalling 100 points, a one-half carat diamond being 50 points, a three-quarter carat diamond being 75 points, and so on.

Larger diamonds are much rarer than smaller ones. In fact, hundreds of tons of rock and ore must be processed to uncover a single one –carat gem quality diamond, and less than one percent of all women will ever own a one-carat or larger diamond.

Since a carat is a unit of measurement and not size, two diamonds of the same carat weight may appear to be different sized depending on how the diamond is cut. Some diamonds will have extra weight on the bottom part – or pavilion – of the stone, and therefore appear smaller.