Many people confuse carat with the size of a diamond. Carat actually refers to the weight of a diamond. The cut and setting of a diamond can make it appear larger or smaller than it’s actual weight. One carat is the equivalent of 200 milligrams and is not to be confused with karat – the measure of purity of gold. One Carat can also be divided into 100 points and therefore a .50 carat diamond is the equivalent of a ½ carat diamond etc.
The term carat is derived from the word carob, a seed that is surprisingly uniform in weight, and was therefore used as a reference for diamond weight in ancient times. A carob seed was said to equal 1 carat.

Another common misconception about diamonds is that a 1 carat is twice the price of a ½ carat. This is not the case. Despite the fact that colour, cut and clarity all effect the price, larger diamonds are found less frequently in nature and 1 carat diamond will cost more than twice as much as a _ carat (with cut, colour and clarity remaining constant). Therefore the larger the diamond the rarer it is and therefore the higher the value.