For any gemstone, the measuring unit of its weight is Carat. A carat is further divided in to 100 points. For example, a diamond measuring 50 points is ½ carat in weight or 0.50 ct. A diamond measuring 75 points in weight is ¾ carat or 0.75 ct in weight. The grading of a diamond begins right from this point. The easiest way to determine the weight of a diamond is this: 1 carat is equal to 0.2 gram Again, there is wide range of possibilities that two diamonds of the same shape cut from the common rough piece can differ based upon the level of proportions. Well, pricing of the diamond do not follow static logic like bullion market. For example, one carat diamond costs pretty higher (much more than double) than the ½ a carat diamond as it’s rare to find a large piece of diamond.