The weight or size of a diamond is measured in carats (ct.). A carat is 0.2 grams and there are 100 points (or 200 milligrams) per carat. A GIE Gemologist’s Scale provides a highly precise diamond weight and this weight is specified in the diamond-report to two decimal points. A .50 ct diamond is the same as a 50-point diamond or 1/2 carat stone. Larger diamonds are rare in nature and hence are more valuable. Carat weight is categorized into groups for example 1 carat, 2 carat etc. This also determines the rarity and value.