Carat refers to weight and therefore the size of a diamond. One carat is divided into 100 points. Therefore, a diamond weighing 50 points is half a carat. Size is the most obvious factor in determining the value of a diamond. But two diamonds of equal size can have very different values, depending on their cut, clarity and colour.
The diamond pictures on the left show the approximate actual size of the different carat weights of diamonds.
The ring pictures below show the same ring with different carat weight of diamonds. Please note these pictures are enlarged but all by the same degree. You can click on any of the ring pictures to view.