The trade values diamonds in price per carat. These figures are much easier to remember as they are usually even numbers. In addition, wholesale price guides list diamond prices in price per carat values. The price per carat increases each time a given color and clarity combination enters the next weight category. Also recognize, as a diamond’s weight approaches the next category the price increases, even though a given price guide may not indicate this. Again, it comes back to rarity. For example, a 1.99 carat is going to be far less available than a 1.50 carat. As a result, it will be a more valuable diamond, demanding a higher price per carat — even though both are in the same weight category.