Carat is the unit of weight for a diamond. Diamonds can range in weight from a fraction of a carat to several carats. One carat equals 0.2 metric grams. A carat can be further divided into points. 1 carat equals 100 points. Therefore, a half carat equals 50 points and a 25 pointer is a quarter carat. When considering diamonds of equal quality, the larger stone will have more value.