The first factor of the 4 Cs that most people hear about is carat weight, which is the best indication of a diamond’s size. Let’s take a minute to cover carat weights in detail to understand how it effects the price.
Diamond weights are measured in ”carats.” One carat equals 1/142nd of an ounce, or 1/5th of a gram. In other words… there are 142 carats in 1 ounce and 5 carats in 1 gram.
The word ”carat” comes from the ancient practice in India (where diamonds were first discovered and traded) of measuring diamond weights with the one thing in nature that is both small and the most consistent in weight — the carob seed. Thus the name ”carat” evolved in the English language, which is still equivalent to approximately the weight of one carob bean.
You also may have heard jewelers talking about ”points” when discussing diamond sizes. This does not refer to the number facets on a diamond, but rather to its weight. Just like one pound is divided into 16 ounces, one carat is divided into 100 points — so each point is 1/100th of a carat. A ”10-point” diamond weighs 1/10th of a carat, and a 50-point stone weighs one-half carat.
Carat weight has a great deal of influence on the price of a diamond — more so than one might imagine at first. Since larger stones are more rare in nature, they are more expensive as well. For instance, one diamond weighing 2 carats will always cost much more than two diamonds of the same quality weighing 1 carat each.
Below is an approximate comparison of the major diamond weights to act as a starting point in your consideration.
To see how diamond sizes vary, see this artical about [glossary id='127' slug='carat' /] weight in our Glossary.
For a complete scientific approach to this question, see our tutorial page about how carat weight affects price.