Carat is the unit of measurement for the physical weight of diamonds. One carat equals 0.200 grams or 1/5 gram and is subdivided into 100 points. For comparison, in units more familiar in the United States, one carat equals 0.007 ounce avoirdupois. Which would require over 2,265 carats to equal 1 pound!
Carat weight is the most objective of the diamond’s 4Cs. All that is required is a precisely balanced scale capable of measuring extremely small weights. Carat weight is measured using a highly accurate, and calibrated digital scale.
Here are some facts about a diamond’s weight and price that are important to understand before purchasing.
Comparing the value of diamonds by carat weight is like comparing the value of paintings by size. A wall-sized canvas by an unskilled artist may be bigger than a miniature by Rembrandt, but it will not be worth more. Large diamonds are rarer than smaller ones, and as the carat weight increases, the value of the diamond increases as well. However, the increase in value is not proportionate to the size increase.
For example, a 1-carat diamond will cost more than twice that of a ½-carat diamond (assuming Color, Clarity and Cut grade are the same). Weight does not always enhance the value of a diamond, either. Two diamonds of equal weight may be unequal in value, depending upon other determining factors such as Cut, Color and Clarity. In fact, if a diamond is improperly cut, the added weight may serve only to reduce its brilliance.
The best way to see the difference in weight versus cut is to look at an AGS Ideal® cut diamond (be sure it comes with an AGS Laboratories diamond grading report or an AGS Ideal® Report from GIA to verify). Then look at the largest diamond in the store that is not an AGS Ideal® cut. You will see a noticeable difference.
Overall, it is important to consult an American Gem Society® jeweler or other credentialed jeweler regarding the weight, quality and value of a particular diamond.