A carat is the term used for the measurement of a diamond's weight. It is equal to 200 milligrams, or 0.2 grams, and there are 142 carats to an ounce. (This is a totally different term from the "karat" weight of gold, which is actually a measurement of purity rather than weight). There are 5 carats to a gram. For jewelry purposes, carats are further divided into points, a one-carat stone equaling 100 points. Therefore, a half-carat stone may be referred to as a "50-pointer," a quarter carat, "25-points," etc. The smaller stones used in pave or channel settings are sometimes called melee. In certificates, appraisals and receipts, however, the weight of your diamond should be written in carats, rounded to 1/100ths, such as .25 carats; .50 carats, 1.20 carats, etc. As the carat weight of a diamond increases, so does its rarity and therefore its price. Because larger diamonds are rare, they generally have a greater value per carat. Generally the price of the stone per carat is determined using the internationally used price list called the Rappaport List or "the List". The price of diamonds go up as they reach milestone weights such as .50ct, .70, .90ct, 1ct, 1.50ct, 2ct etc. Because of this price configuration diamond cutters will never consciously cut a diamond to be a .95 when it's possible to make it a 1 carat stone or a 1.90 if it's possible to make it a 2 carat stone even if it means giving up a better cut. Therefore a stone that is .99 carats is very hard to find. It looks like a 1 carat diamond but it doesn't cost it. How you throw your weight around. Carat weight does not always reflect appearance. You can have a .90 carat diamond appear larger than a 1 carat diamond if it is cut shallower. So always be conscious of the Measurements and the Depth Percentage as they are more accurate indicators of how the carat weight will show itself.