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Tips on Choosing a Diamond Size

How to Choose the Perfect Diamond Size

Choosing the right diamond size for your ring is one of those things that requires a bit of insider knowledge, and we're more than happy to share our expertise with you.
How many carats are in the average engagement ring?

The short answer is the number of diamond carats varies and is based on factors such as ring setting size, ring design and pricing considerations. A luxurious ring may have .24 carats or 1.00 carats.

When looking at carat size, it's best to think in terms of fractions and points. Don't worry, you don't have to be a math whiz. We provide an easy chart below. To get an idea of how this works, let's consider the following:

  • How big is a 1/4ct diamond?
  • How big is a 3/8-carat diamond?
  • How much is 5/8 of a carat diamond?

See our chart below for quick answers to the above questions.
Here's a more detailed explanation about carat sizing:

Weight vs. Size:
Diamonds are sold according to weight, which is measured in carats* and points. To illustrate, think of this: When you buy bananas at the grocery store, they are put on a scale and sold to you by weight, and that weight is pounds and ounces. Diamonds are sold the same way; they are put on a scale and sold by weight, but that weight is carats and points.

A carat is subdivided into 100 points, so a diamond weighing 75 points is a 3/4-carat diamond, 33 points is 1/3-carat, 150 points is a 1.5 carat, and so on. Points are not to be confused with facets, however, which are the cut surfaces of the diamond.

Points are measured within ranges, so that a ¾-carat diamond may be between 69 and 82 points and still be considered a ¾-carat. Note the table below.

Fraction Points Approximate mm width
(round diamonds)
1/4 carat
= .23 - .28
1/3 carat = .29 - .36 4.4mm
3/8 carat = .37 - .44 4.8mm
1/2 carat = .45 - .58 5.2mm
5/8 carat = .59 - .68 5.5mm
3/4 carat = .69 - .82 5.8mm
7/8 carat = .83 - .94 6.2mm
1.0 carat = .95 - 1.05 6.5mm

Diamonds are most accurately weighed when they are not mounted in a setting. In fact, most gemological laboratories will only grade loose diamonds - meaning, diamonds that are unmounted. If other factors are equal, the more a stone weighs, the more valuable it will be. Note in the image below that a 2-carat diamond does not appear to be twice the size of a 1-carat diamond when viewed from the top.

Mouse over (or tap if on a phone or tablet) the different diamond sizes below to get an idea of how each size appears.

Click here to design your perfect ring

What is the most brilliant diamond cut?

Classic round cut diamonds offer a tremendous amount of brilliance compared to other cuts. The sparkle is truly magnificent!

Our Take: Deciding on diamond size is really about striking a balance between carat weight and quality. Men, don't get so caught up in the technical aspects of grading that you lose sight of the romance surrounding this purchase. Our 30 years of experience in the jewelry business has taught us that nearly 100 percent of women would rather have a 1-carat diamond of good quality, than a 1-carat diamond of excellent quality. Selecting a diamond in the near colorless range (G-J), and SI1 or SI2 clarity, would allow you to get a larger diamond that is still beautiful. Diamonds within these ranges are considered to be the best value, and are the most sought after by consumers.

*When spelled with a C, carat is a unit of weight. When spelled with a K, karat refers to purity of gold.