A diamond's weight is measured in 'carats', which is a small unit of measurement equal to 200 milligrams. The term 'Carat' is different from 'Karat', which measures the purity of gold.

The carat weight is extremely important in determining a diamond's value. Bigger diamonds are more rare, and the value increases exponentially as the size of the stone increases. A two-carat stone of the same grade will cost much more than twice the amount of a one-carat stone. Remember that size is only one of the factors for choosing a diamond, you should also consider the cut, colour and clarity of the diamond.