Our final installment on the four C's of diamonds addresses carat, or carat weight. Carat refers to the weight of a diamond. There are 100 "points" to a one carat diamond, so a 33 point diamond is a 1/3 or .33 carat diamond, a 50 point diamond is a 1/2 or .50 carat diamond, etc.. Diamonds weighing over one carat are written out as 1 1/4 or 1.25 carat. Carat is a pretty straightforward concept, perhaps the easiest of the four C's to understand. Carat weight is determined by weighing a diamond on an industry-approved diamond scale. All things (cut, color, and clarity) being equal between two diamonds, the heavier of the two will be more expensive.
GIA has yet another excellent four C's tutorial on carat weight.