Round Brilliant Cut Diamonds: Ask a Diamond Expert

Angelica Frey | July 11, 2023

Round cut diamonds are the most popular of all diamond shapes in the world both for popular engagement rings and fine jewelry. Beyond its timeless and versatile appeal, the Round Brilliant cut itself was created for ultimate brilliance. The unique arrangement of its facets is optimal for interacting with the light, which is why the Round Brilliant is considered the most brilliant diamond of them all.

GIA graduate gemologist Queena Chang and and VRAI’s Sr Director of Sales & CX Grace Taylor sat down with us to offer their insights into Round cut diamonds. Discover why this beloved VRAI created diamond shape might be right for you.

What Is A Round Diamond?

Round Cut diamonds are round-shaped diamonds with brilliant faceting. A Round Brilliant diamond has 57 or 58 facets, and the table helps gather light from above and either reflects it back to the observer or directs it into the diamond’s interior. The crown facets consist of 8 bezels, 8 stars, and 16 upper halves. They gather and disperse light to create brightness, fire, and a scintillating pattern of light and dark.

The pavilion facets, consisting of 16 lower halves, 8 mains, and an optional culet, reflect the light back through the crown to the viewer’s eye.

A Round diamond is a work of mathematical precision meant to maximize brilliance. Diamond cutter Marcel Tolkowsky, who developed the Round Brilliant cut in 1919, highlighted the ideal proportion as 100% diameter, 53% table, 43.1% pavilion and 16.2% crown. He exposed his theories and findings in Diamond Design, which is now part of the public domain. Tolkowsky’s proportion has, since then, been tweaked and perfected.

The History of the Round Cut

The development of the Round diamond had been at least six centuries in the making. The oldest precedents are known as the “Single Cut” diamond, the “Mazarin” diamond, and the “Peruzzi” diamond.

The Old Mine and Old European cut constitute a historical precedent to the Round Diamond. Old Mine cuts were mostly cut between the 18th and 19th century, and have a chunky faceting pattern, but vary in shape: some are rounder, others more rectangular. Old European cuts were cut in the 19th and early 20th century and have a harmonious round shape. Both Old Mine Cut and Old European diamonds were cut by hand, and there was no standard. This means no two Old Mine or Old European diamonds are alike.

“One of the oldest cuts for diamonds is the Old Mine Cut, which was first popularized in the Georgian and Victorian Eras. This shape was achieved by taking a mined diamond’s octahedron shape, and rubbing two of them together to form the soft cushion/off round outline, and then faceting the 57 or 58 facets that we now see in modern Round Brilliants,” explains VRAI’s Chief Diamond Expert Queena Chang.

In 1873, Boston diamond cutter Henry Morse invented the bruting machine. This made the creation of a symmetrical outline and faceting pattern easier for the cutter. It allowed them to cut diamonds into precise round shapes without following the outline of the original crystal.

Morse also invented the first gauge to measure the angles of diamonds. He is credited for the invention of the American cut, one of the forerunners of the modern round brilliant cutting style. It’s notable for this having a lower crown, a larger table, a shorter pavilion, and smaller culet compared to the Old European. Morse is famous efor being among the first cutters who emphasized cut and brilliance over size.

Belgian-born Marcel Tolkowsky standardized the formula for the Round Brilliant diamond in 1919, which, thanks to technological advances, has since been perfected. In the 1950s, R. W. Ditchburn applied Tolkowsky’s principles to fancy-cut shapes that have brilliant faceting, such as Oval, Marquise, and Pears.

In the fall of 2004, GIA’s own Thomas Moses published A Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds for their quarterly journal Gems & Gemology.

Most Famous Round Diamonds in History

The Round Brilliant cut is a newer shape compared to others, so the most notable pieces are more recent in history.

The Martian Pink is a 12.04 pink, Round diamond that was named by Jeweler Ronald Winston in 1976 and was sold at auction in May 2012. Christie’s described it as "the largest round fancy intense pink diamond to ever go under the hammer,” The BBC reported.

The Premier Blue Diamond is a 7.59-carat round fancy vivid blue diamond offered as the top lot in Sotheby’s Hong Kong Magnificent Jewels and Jadeite sale on October 7, 2013 at the Hong Kong Convention and Exhibition Centre.

In 2018, Sotheby’s auctioned what was then known as “The Largest Flawless D Round Diamond ever graded,” and it weighed 102.34 carats.

In 2021, Sotheby’s also sold an unmounted Round diamond weighing 50.03 carats with a GIA report stating that the diamond is G color, VVS2 clarity, with Excellent Cut, Polish and Symmetry.

How to Buy a Round Diamond

A Round diamond is a diamond shape that looks closest to its carat weight. Its brilliant facets give it unprecedented brilliance, and, if well cut, they can offset a low color grade and the presence of blemishes and inclusions. A Round diamond is the result of centuries of tinkering in terms of proportions, so when it comes to the 4Cs, the cut is the most important of the four criteria.

Evaluating Round Brilliant Diamonds

In the case of Round diamonds, a diamond’s cut grade is the most indicative of its appearance, as the proportions among angles, facets, crown, table, and pavilion determine how the light is reflected and dispersed.


The Round diamond is the only diamond shape with an official cut grade. Round brilliant cut diamond has 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion that’s known as the culet. The large, flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. It is important to note that a wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light and how attractive the diamond is to the person viewing it.

A thick girdle increases the diamond’s depth, making the diameter of the diamond smaller. A steep crown and pavilion angle limit the diamond’s fire and scintillation. The opposite conditions will yield similar results: if the pavilion and the crown angles are too shallow, it causes a lack of contrast and limited scintillation.

Don’t sleep on the further grading parameters such as Symmetry and Polish. Symmetry indicates the alignment and shape of the diamond’s facets, while, within the GIA diamond grading system, Polish evaluates the quality of a diamond's surface condition as a result of the polishing process or to blemishes created after the cutting process.

Clarity and Color

A high-cut grade can mask clarity characteristics, especially at lower carat weights. What’s important is choosing a diamond that’s eye-clean, meaning it doesn’t have any inclusions that are visible to the naked eye. It’s best to devote one’s budget to an Excellent cut grade.

With Round diamonds, you have some leeway in terms of color as well, provided that you prioritized cut. In fact, to the naked, untrained eye, Colorless and Near Colorless diamonds are virtually indistinguishable. Colorless (DEF) diamonds do not have any color that's visible to the eye, and they are ideal for any white gold and platinum engagement ring or jewelry design that won’t further imbue them with color.

Near colorless diamonds (GHIJ) are diamonds that, when they face up, still appear colorless to the naked and untrained eye. Most people are unable to tell DEF diamonds apart from GHIJ ones without comparing them side by side against a white background.


The Round diamond is the diamond with the most balanced weight-to-size ratio thanks to its symmetrical shape and thanks to the standardized proportions between crown, table, and pavilion. Just keep in mind that carat refers to the diamond’s weight, not to its diameter: a 1 carat Round diamond measures 6.5mm in diameter, while a 2 carat diamond is around 8.1mm in diameter. A 2-carat diamond will weigh double the weight of a 1-carat diamond, but only be between 55 and 60% larger.

Pros and Cons of the Round Cut Diamond

With symmetry, a good weight-to-size ratio, and unprecedented brilliance, you would find it hard to find any drawbacks to the Round diamond.

“There’s a saying in the diamond world that nothing sparkles like a round brilliant, and it’s true! Rounds are optimally designed for light return, so they’re super sparkly,” says Taylor. “Some people find that their immense popularity is a downside - they’ve always been the most popular shape and they probably always will be.”

Top 3 Best Round Diamond Settings

“Round really works in every setting!” explains Taylor enthusiastically. “Because it’s kind of the default, most settings are designed with round brilliant centers in mind.”

The Knife Edge solitaire highlights the symmetry and harmony of the Round diamond. A Graduated Band engagement ring with a Round at its center is the ultimate expression of this shape’s beauty. The Double Band engagement ring creates a look of two parts (two parallel bands) working in synergy for a greater whole (the center diamond).

two engagement rings next to a ring sizer and package
two engagement rings next to a ring sizer and package

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How Large Does a Round Cut Diamond Appear?

A diamond’s carat weight shows differently, depending on the diamond shape. A Round Brilliant is often considered truest to its carat weight. Moving up in carat weight does impact its appearance, but going from 1 to 2 carats does not automatically double its perceived size.

On average, a 2-carat Round Brilliant cut diamond will appear around 50% larger than a 1-carat diamond of the same shape. And a 3-carat Round Brilliant cut diamond will appear around 15% larger than a 2-carat diamond of the same shape (so roughly 65% larger than a 1 carat Round).

What Diamond Shapes Share Similarities With the Round?

Round diamonds have brilliant facets, so if brilliance is your main focus, Oval, Cushion, Marquise, Pear, and Trillion will have a similar, yet not identical, scintillation pattern. “From our core collection of shapes, the Trillion is going to give you a really similar faceting style, and cushion can give you a similar feel on the hand (especially set in a 4 prong setting),” explains Grace Taylor, VRAI’s Senior Director of Sales and Customer Experience.

From our Cut for You™ program, Taylor recommends the Harmonia, Passion, Regulus, Round Rose, and Octavia. “These all have a round profile with unique facets,” she explains.

VRAI Created Diamonds

VRAI only sells lab created diamonds grown in our certified zero-emission foundries, powered by 100% renewable energy. This means all VRAI created diamonds are no mining, no human toll, no emission, no guilt diamonds. This lowers the cost of lab grown diamonds for customers so you get more carats for less!

virtual appointment with diamond expert meeting with potential customers over a call on a computer
virtual appointment with diamond expert meeting with potential customers over a call on a computer

Consult with a diamond expert

Speak with our diamond experts and enjoy:

  • Personalized guidance to select your ring
  • In-depth diamond 4C education
  • Exclusive in-store fittings or virtual try-ons
  • Custom design options

Speak with our diamond experts and enjoy:

  • Personalized guidance to select your ring
  • In-depth diamond 4C education
  • Exclusive in-store fittings or virtual try-ons
  • Custom design options