Round cut diamond guide and size chart

Timeless elegance and jaw-dropping sparkle both come to mind when you envision a diamond with this instantly recognizable shape: the modern round brilliant. At Lightbox, we’ve captured the iconic brilliance of this classic cut with our dazzling signature hues of pink, white, and blue lab-grown diamonds for all occasions. The always stunning round cut diamond has evolved through the years and today, it continues to shine as one of the most popular lab-grown diamond shapes at Lightbox. 

Discover the rich history of the round brilliant cut, its awe-inspiring characteristics, our top styling tips, and how to choose the perfect round cut lab-grown diamond for your Lightbox jewelry collection.

What is a round brilliant diamond?

The round brilliant cut diamond is a widely popular diamond shape in both natural and lab-grown diamonds. It features an unmistakable circular silhouette and a cone-like shape—with 58 perfectly placed facets (including the culet). It’s these carefully constructed facets that allow light to perform in a way that’s unparalleled by any other cut. Although other types of round cuts exist—like the vintage old European and rose cuts—the majority of round diamonds seen today are round brilliants.

Throughout the jewelry world, round brilliant cut diamonds are some of the best-selling diamond shapes of all time (dominating about 70% of all natural diamonds sold, to be exact). In Lightbox designs, our round lab-grown diamonds offer eye-catching sparkle and brilliance that instantly steal the show.

The history of round cut diamonds

The round brilliant diamond has left its mark throughout history as an iconic shape in truly unforgettable diamond jewelry—including the engagement rings of Britney Spears, Mila Kunis, Princess Beatrice, and even Queen Elizabeth’s legendary three-carat platinum-set ring. Believe it or not, the classic appearance of the round cut diamond has been developed by some of the world’s top diamond cutters over generations that span more than one hundred years. This shape made regular appearances throughout the Edwardian, Victorian, and Art Deco eras—in the form of the old European cut—but it wasn’t until the invention of the bruting machine in the late 1800s that it was modified to create greater scintillation (also known as sparkle).

In 1919, the popularity of natural round cut diamonds really soared when diamond cutter Marcel Tolkowsky published his thesis, titled “Diamond Design: A Study of the Reflection and Refraction of Light in Diamond.” Tolkowsky’s specifications laid out the ideal proportions for maximizing fire and brilliance in a natural round cut diamond, and created the 58-facet gold standard that we know and love today.

How to choose a round brilliant diamond

Whether you’re looking for a round brilliant—or any other lab-grown Lightbox diamond shape—the 4C’s of diamond buying should always be your go-to guide. With that being said, there’s a few important considerations to note when it comes to round diamonds in particular. Keep reading to find our top tips for choosing the perfect Lightbox lab-grown round brilliant diamond for you.


The fire and brilliance that we all love so much about a natural or lab-grown diamond are an extension of the quality of the stone’s cut —and no other shape sparkles quite like a round brilliant. The captivating light that’s reflected from the 58 precise facets of a round brilliant stone is created through mathematical calculations advanced over decades to create ideal symmetry and proportions. For over 50 years, the team at Lightbox has been utilizing the leading technology to create laboratory-grown diamonds that are all measured as having at least a “Very Good” cut, to ensure exceptional brilliance, fire, and scintillation.

When it comes to natural diamonds, it’s important to note that round brilliants are graded very strictly by diamond grading labs — and the cutting standards for these stones are generally considered to be very high. In fact, the round brilliant is the only shape that receives a cut grade from the GIA (Gemological Institute of America). In the case of lab-grown diamonds, ​​the GIA and IGI both offer dedicated reports using the same grading process as natural diamonds, with a special specification that the origin of the round stone is lab-grown.


Everyone can have a slightly different preference when evaluating the color of a natural round brilliant diamond, but here’s some good news: The incredible brilliance of this diamond cut may actually show color less than any other shape. In other words, the superior light reflection of a round brilliant can help conceal color and make a natural diamond appear brighter. With Lightbox lab-grown diamonds, you never need to worry about deciphering between colors, since all of our lab-grown round diamonds are categorized as “near colorless” for a consistent, high-quality color grade -- and our Lightbox Finest™ stones are 'colorless D, E, F', the highest grades a stone can be.


The exceptional light of natural round brilliant diamonds can also help disguise visible inclusions better than any other cut — meaning you’ll be less likely to notice flaws with the naked eye. In natural round brilliant stones, you might want to opt for inclusions around the perimeter, as these may be less noticeable through the table (or top, flat surface) of the diamond. We believe that one of the major benefits of lab-grown diamonds is the ability to create round stones that consistently reach our top clarity standards of VS clarity or better for magnificent beauty and value.


Lightbox’s core collection of lab-grown round brilliant diamonds are always priced at 800 USD per carat (or 1500 USD for our Lightbox Finest™ stones with each being produced to the same transparently priced standard. For natural stones, keep in mind that round brilliant diamonds are generally considered to be the most expensive shape. This is largely due to their unrivalled sparkle, continually high demand, and the fact that their carat weight yield is fairly low. To learn more about the competitive pricing of our lab-grown diamonds, check out our diamond pricing guide.

How to style your round brilliant diamond

When it comes to effortlessly styling your lab-grown round brilliant diamond jewelry, you’re in luck — this shape works with almost any design or metal, including our white gold, yellow gold and rose gold. Luckily, diamonds with a round cut have been on-trend for centuries, and they aren’t going out of style anytime soon. There’s a good reason this shape is the most popular among all types of diamonds, after all! The universally flattering style of a round brilliant is an eternal classic. Although its original claim to fame is in breathtaking natural diamond engagement ring designs, the round brilliant is extremely wearable in all of our lab-grown diamond styles — especially in our necklaces and earring.

Since the beauty of this shape can stand on its own, we recommend a simple solitaire setting to fully highlight the unbeatable fire of the round brilliant cut. Other popular styles include delicate micro-pavé or halo settings—like this pair of 1-carat lab-grown diamond halo earrings. They’re also the perfect way to highlight the distinctive beauty of Lightbox’s lab-grown colored diamond jewelry.

Caring for your round brilliant diamond

The round brilliant makes an excellent choice for all lifestyles, as long as proper jewelry wear and care instructions are followed. This means keeping your jewelry away from harsh chemicals, cleaning supplies, and checking the prongs periodically to make sure they are still secure. Unlike some of the other diamond shapes—like the sharp, angular corners of the princess cut (which can be more prone to snagging or chipping, depending upon the setting used)—the round brilliant is considered very durable and versatile. At Lightbox, all of our prongs are expertly hand-set on each design to ensure that your round lab-grown round diamond is always protected. 

Regardless of your style or budget, there is always room for the unbeatable fire and brilliance of a lab-grown round brilliant diamond in everyone’s jewelry wardrobe.

  • Our environmental commitment

    At Lightbox we are big on transparency and our commitment to reducing the footprint of our stones is a huge part of this. See more on how we grow our stones with 100% renewable energy.

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  • Visit the lab

    Explore the Lightbox Lab in Portland, Oregon, home to our world-leading technology producing up to 200,000 carats a year, each one always VS clarity, very good cut and now 'grown in the USA'.

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