As with all precious stones, the weight–and therefore the size–of a diamond is expressed in carats.
One carat is divided into 100 “points” so that a diamond of 25 points is described as a quarter of a carat or 0.25 carats. Size is the most obvious factor in determining the value of a diamond, but now you know that two equal sizes can have very unequal prices depending on their quality. However, remember that diamonds of high quality can be found in all size ranges. The previous chart shows other examples with the approximate size of diamonds of varying carat weights.