The carat is the measurement unit used to calculate the weight of diamonds (ct). In contrast to one gram, a diamond carat weighs 0.05 grams or five carats. A 2 carat ring cost may be significantly impacted by its carat weight. A diamond becomes rarer as it increases in size and carat value. This is so that a diamond cutter can make smaller diamonds more quickly than they can find a piece big enough to make a 2-carat stone.