Round Cut Diamond Buying Guide

By Michael Fried

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Bottom Line Recommendation:

For an exquisite Round Cut Diamond, pay close attention to the diamond’s Cut quality. Review the GIA report and ask an expert for assistance. When it comes to Clarity, we recommend looking a diamond that is eye clean like this beautiful SI1. To go higher than that in Clarity is paying for something that will go unnoticed. For Color, we recommend the J Color for white gold solitaire rings like this beautiful Round Cut in a 18K white gold setting. And for yellow gold solitaire rings, we recommend K or L Color like this Round Cut in 18K yellow gold.

For assistance in selecting the highest quality Round Cut at an exceptional price point, contact our diamond experts.

The Round Cut Diamond

As the most popular Diamond Shape, the Round Cut Diamond represents over two thirds of all diamonds sold.

The Round Brilliant Cut boasts 58 facets (including the culet) and offers exceptional white light reflection, also known as brilliance. With a classic, timeless appearance, Round Brilliant Cuts are often used in engagement rings, necklaces and other fine jewelry pieces. This 1.0 Carat stone is a stunning example of a Round Brilliant Cut.

In 1919, Marcel Tolkowsky created a surge of interest in the Round Cut Diamond by publishing his work, “Diamond Design: A Study of the Reflection and Refraction of Light in Diamond” which highlighted the ideal cut aspects of a Round Brilliant. Since Tolkowsky’s influence, the Round Cut has remained the most common diamond cut.

Prior to the 20th century, during the Edwardian, Art Deco and Victorian eras, the Old European cut was a popular diamond choice. As knowledge and technology advanced over time, diamond cutting techniques became more refined. Cut design progressed toward larger tables, smaller culets and longer, leaner facets. While Old Europeans were cut primarily for color, the Round Brilliant is cut for brilliance.

The primary difference between the Old European and the Round Cut is that the Old European maintains facets with triangular blocks while the Round Brilliant has thinner facets. Some customers enjoy the vintage style and personality of the Old European, though most prefer the brilliance of the Round Cut.

Round Cut Diamond — Cut Quality

Of all the characteristics, Cut quality is the element that most heavily impacts a diamond’s beauty. It encompasses how well-proportioned and aesthetically appealing a diamond is. Cut proportions affect a diamond’s ability to reflect light and provide brilliance.

The GIA is a well-respected and renowned lab grading entity that issues reports for diamonds. They grade Round Brilliant Cuts on the following scale:

    • Provides the highest level of fire and brilliance.
  • Almost all incoming light is reflected through the table.
Very Good
    • Offers immense brilliance and fire.
  • Majority of entering light reflects through the table.
    • Provides ample yet not overwhelming brilliance.
  • Much of the light reflects through the table.
    • Offer minimal brilliance.
  • Light exits through the sides and bottom of diamond.
    • Yield nearly no sparkle or brilliance
  • Light escapes from the bottom and sides of diamond.

While GIA grade is important, it is not the sole aspect to consider when it comes to Cut. Be sure to keep this in mind as you search for diamonds, as roughly 55% of all GIA round diamonds listed on the internet are Excellent cuts. This means there is a wide range of “excellence” within their grade (ranging from truly stunning to mediocre).

To evaluate a diamond’s Cut quality, ensure it is not cut too shallow or too deep.

When a Round Brilliant is cut too shallow, incoming light strikes the pavillion at a low angle. The light then travels through the diamond and exits through the sides, without reflecting through the table to the eyes. The large amount of escaping light causes the diamond to lack both brilliance and fire.

If a diamond is cut too deep, light will strike the pavillion at a sharper angle, prompting the light to reflect to another pavilion and exit through the bottom of the diamond—instead of through the table. For this reason, when a diamond is cut too deep, it will be dull instead of radiant.

When a diamond is cut for maximum brilliance and fire, light strikes each pavilion and reflects back to the eye through the crown and table. A well-proportioned Round Cut Diamond with optimal facet angles reflects white and colored light almost flawlessly.

How Light reflects through a diamond

Because Cut quality impacts your diamond’s beauty the most, we strongly recommend detailed attention in this area. If you’re working within a budget, consider reducing your Carat weight to ensure you purchase a high quality cut.

Rather than making a decision based solely on a grading report, review the diamond closely and ask for an expert’s opinion.

What is a Brilliant Cut Diamond?

A Brilliant Cut Diamond refers to a specific form of Cut that utilizes numerous facets to reflect white light particularly well. The Round Brilliant Cut, for example, has 58 facets (including the culet) and embodies a cone-like shape, like this Excellent Cut Round Diamond from James Allen.

A depiction of a Brilliant Cut’s facets—including its crown, pavilion and table facets—is displayed in the image below. Depths, angles and proportions work together to generate a diamond’s ability to emit fire and brilliance. Because Brilliant Cuts have a large number of carefully constructed facets, light reflects off of them in a remarkable way.


What is an Old European Cut?

The Old European Cut is similar to the Round Brilliant, but was designed prior to modern diamond technology. Old European Cuts generally have smaller tables, heavier crowns and deeper proportions than the modern Round Brilliant Cut.

The GIA currently considers the following to be a diamond with an Old European Cut:

    • Size of table: Equal to or less than 53 percent
    • Crown angle: Equal to or greater than 40 degrees
    • Bottom half facet length: Equal to or greater than 60 percent
  • Size of culet: Larger than modern Brilliant Cut culets


Round Cut Diamond — Clarity

Diamond Clarity refers to the the visual appearance of inclusions and blemishes in a stone.

The GIA grades Clarity on the following scale (from cleanest to most included):

    • IF: Internally Flawless
    • VVS1: Very Very Small Inclusions 1
    • VVS2: Very Very Small Inclusions 2
    • VS1: Very Small Inclusions 1
    • VS2: Very Small Inclusions 2
    • SI1: Small Inclusions 1
    • SI2: Small Inclusions 2
    • I1: Inclusions 1
  • I2: Inclusions 2

For the Round Cut Diamond, or any Diamond Shape for that matter, it is most important to determine if the diamond is eye clean—rather than simply reading the Clarity grade on a report. In other words, do you see any inclusions, blemishes or dark spots when looking at the diamond without magnification? In many cases, a VVS2 diamond and a VS1 diamond appear identical to the naked eye: free of any inclusions. Although they will look the same to you, the cost of the VVS2 will be much higher. For example, this stunning SI2 diamond saves you almost 25% over a mediocre VS2 like this one.

In addition to looking for inclusions, watch for their locations. If blemishes rest on the perimeter, they will be harder to see through the diamond’s table. They may also be eventually covered by jewelry prongs once the diamond is set. Check out our guide on VVS diamonds for more information on how to locate inclusions.

As a general guideline, we suggest looking for a diamond that is eye clean, and not choosing a higher Clarity grade than this. There is no reason to go higher than this, and pay more for something that will go unnoticed. As an example, you may find a stunning S1 with inclusions near the edge, making them hardly noticeable or covered by jewelry prongs once set in a ring.

Review the diamond closely yourself through high level technology like that of James Allen and ask an expert to double check your work before a purchase.

Round Cut Diamond — Color

Because Round Brilliant Cuts reflect more light than any other Diamond Shape, Color is more difficult to distinguish. The diamond’s multiple facets and high level of brilliance contribute to concealing Color, making Color a component that should be reviewed but not overemphasized.

On a scale from D to Z, a GIA lab report will indicate the level of tint or color within a diamond. D signifies a clear, colorless diamond while Z means easily recognizable brown or yellow tint. To the naked eye, however, the differences between two adjacent grades (such as G and H) are rarely noticeable.

For a closer look at the slight difference between Diamond Color grades, let’s review the chart below. In the image, two sets of identical diamonds are shown. On the right, the nine diamonds are arranged face down in order based on their Color grade. On the left, the diamonds are arranged randomly.

When looking at the photos on the left, are you able to identify the correct grading order?

(Answers (left side): First Row = G, L, E. Second Row = F, J, D. Third Row = H, K, I.)

As you probably noticed, the eye has a difficult time deciphering any one element of a diamond, such as Color, in this case.

As another example, the Color of this H graded diamond with SI2 Clarity in a 14K white gold setting looks identical to the Color of this I graded diamond with SI2 Clarity in a similar setting, while the diamond cost is nearly 8% more. Even an expert would have a hard time noticing the Color difference under 10x magnification.

In addition to reviewing the diamond for Color, consider the setting that will be used. A diamond should appear colorless in relation to its setting. For example, this I Colored Round Cut looks colorless in a 14K white gold setting and this K Colored diamond looks white in relation to its 14K yellow gold setting.

In general, we recommend the J Color for white gold solitaire rings and K or L Color for yellow gold solitaire rings. We strongly encourage viewing the diamond closely and asking an expert for assistance. It could save you hundreds or even thousands of dollars in an area that will likely go unnoticed to the naked eye.

For more information on Diamond Color, check out our Diamond Color Guide.


If you’re looking for a timeless Diamond with impressive brilliance, a Round Cut Diamond may be the perfect choice. Consider first the quality of the diamond’s Cut, then its Color and Clarity, to ensure the most stunning Round Cut Diamond.

To confirm you’re making a smart purchasing decision, contact one of our experts who can help with reviewing and identifying high quality diamonds.

About the author
Mike learned the diamond business from the ground-up at Leo Schachter Diamonds - one of the world's top diamond manufacturers. He has been recognized as a diamond industry expert by Time, PeopleMoney, The Daily Mirror, NerdWallet, The Times Herald, Yahoo Finance Australia, The Art of Charm, The Washington Diplomat, The Next Web, and more. See more
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