Carat size is the simplest of the four "C's" to measure a diamond's quality. However, it is not a direct measure of size (like inches or millimeters) but a measure of weight. Each carat is equivalent to 200 milligrams, or about .007 ounces. There are 100 points in a carat, so a "33 pointer" equals a third of a carat or .33 carats. Diamonds of the same weight can differ based on other factors, especially the cut, which influences size. The correlation of size to value is an obvious one. The larger a diamond is, the more valuable it is.