Diamonds are weighed in units called carats. A carat is measured in increments called points. One carat is equal to 100 points. Carat weight is the easiest of the 4C's to determine because it is measured on a diamond scale. Two diamonds of equal weight can have very unequal value depending upon the cut, color and clarity of each.
Very small differences in carat weight can sometimes result in a disproportionate cost. To the naked eye, the difference between a 1 1/10 carat and 1 1/5 carat diamond might be impossible to discern, but the cost difference between those carat weights can be significant for otherwise comparable diamonds.