The unit of measure used for the weight of a diamond is the carat. As a matter of reference, a carat is equivalent to .2 grams or .007 of an ounce. Carat weight can also be divided further by using points. There are 100 points in one carat. So a 1/4 (.25) carat stone can also be expressed as 25 points and mean exactly the same thing. When comparing two diamonds, please note that just because one is twice the carat weight of the other does not mean that it will appear to be twice the size.