Carat

This, of course, is the first thing people think of and notice about diamonds, especially engagement rings. "How big is it?" is often the phrase that follows "Congratulations!" when you hear that someone is engaged. However, "bigger is better" is not always the best advice when selecting a diamond.

 
 

Diamond Math

Everyone knows that a bigger diamond is more expensive, but the price increases are not that straight-forward. For example, a one carat diamond should cost about twice as much as a similar half-carat diamond, right? Not true. The price of a diamond increases exponentially as the size goes up. So, if the half-carat stone costs $5, then a one carat stone may cost $15 and a two carat stone may cost $50.

Big Points and Big Leaps

There are certain points as a diamond's size increases where the price does even more gymnastics. For example, going up two to four points doesn't usually have a great impact on the price of a diamond. However, if that increase crosses any of the "big points," the price will take a "big leap."

1.00, 2.00 The whole-carat marks are obvious points where the price of a diamond will make the biggest leaps in price.

0.25, 0.50, 0.75 The quarter-carat marks also create obvious "big points" where price may leap.

0.33, 0.65, 0.90These are less obvious points where price may leap. These leaps will be the smallest.