Why does my 1 ct diamond look smaller than hers?

In our 4c’s blog we talked about Carat Weight and how it is commonly confused with the size of the diamond. Diamonds are sold by weight and not by visible size or measured diameter. The size of a diamond refers to the dimension measurements, while carat weight is just that, the weight of the diamond. Size can be used to estimate the weight of a diamond and vice versa, but it is not always accurate because there aren’t set measurements for each weight.

The measurement most consumers are concerned about is the face up size, rightly so, since that is what you see the most of when looking down on a ring. The measurements and proportions that affect the cut grade and brilliance of the diamond are also very important. Size is determined first by the shape of stone the cutter wants the diamond to be made into, and second by how much weight the cutter thinks can be retained while still keeping an excellent cut grade and brilliance.

Just like snowflakes all diamonds are different. Even if two diamonds are the same basic shape and weight, their dimensions and proportions are slightly different.

If two diamonds are of the same average diameter and quality, but different weights, the heavier diamond will cost more. This is known as Weight Ratio, which is used by GIA in its Diamond Cut Grading system to determine hidden weight. For example, if you have two diamonds that both weight 1 carat, but one of them looks a lot smaller than the other that is because of dimensions and proportions. A deep cut is smaller in diameter and a shallow cut is wider in diameter. A shallow cut makes a diamond look bigger on the top (spread), but diamonds that are either too shallow or too deep sacrifice ‘Cut’ quality and therefore, brilliance. A deeply cut diamond has most of its weight hidden in its depth, making it appear smaller than a well-cut diamond of the same weight.

Just because the proportions of a diamond are a little off of ideal is not necessarily a bad thing. The most important part thing about the cut grade of the diamond you are considering is that it will have the most brilliance and have a reasonably sized visible area.

(Diamond Size vs. Carat Weight: What Is the Difference?, 2017); (Get to Know Your Diamond, 2017); (ILENE REINITZ, 2017)