Diamonds 101: Round Diamonds

Round diamonds are classic, versatile, and beautifully brilliant. They’re also incredibly popular. Well over two-thirds of all diamonds sold today are round diamonds. It’s clear that many people adore round diamonds— but is this top diamond shape right for you? We’re here to help you decide for yourself with a new edition of Diamonds 101.

In this Diamonds 101 guide, we’re going over everything you need to know about round diamonds. We’ll cover the definition and anatomy of the round cut diamond, share why round diamonds are so popular, detail how to buy a round cut diamond, and answer the most frequently asked questions about round cut diamonds.

What Is a Round Diamond?

Round diamonds are diamonds that have a round shape when viewed from above. There’s more than one way to cut a round diamond. However, the vast majority of round diamonds have a very specific cut: the round brilliant cut.

The round brilliant cut was invented by Marcel Tolkowsky in the early 1900s. Tolkowsky, an engineer who came from a family of diamond cutters, studied the optics of diamond cuts as a part of his Ph.D. thesis. His goal was to maximize light performance in round diamonds by figuring out their ideal cut and ideal proportions. He later published his findings in the 1919 book Diamond Design: A Study of the Reflection and Refraction of Light in a Diamond. In that book, he described a specific set of angles and proportions that he believed would maximize a round’s diamond’s scintillation.

Tolkowsky’s findings had an incredible impact on modern diamond cutting. His formula created a much more brilliant round diamond, which we now know as the round brilliant cut diamond. Today’s round brilliant cut has been refined over the years to create an even more brilliant round diamond that features 57 facets and an optional culet. A modified version of the brilliant-cut is also featured on many other modern diamond shapes, including oval-shaped, cushion cut, pear-shaped, marquise cut, and princess cut diamonds.

A Note on Round Brilliant Cut Diamonds vs. Other Round Diamond Cuts

When people talk about round diamonds today, they’re usually referring to round brilliant cut diamonds. However, there are other types of round diamonds. Two lesser-used, yet notable round diamond cuts are the old European cut and the rose cut.

The old European cut was a very popular diamond cut from 1890 to 1930. It was the most popular round diamond cut until the round brilliant came along. Old European cut diamonds have triangular block facets that create a flashier, chunkier type of light reflection compared to the round brilliant’s fragmented shimmer. It’s quite rare for a diamond cutter to create a new old European cut, so most diamonds with this cut are antiques.

The rose cut is another antique diamond cut, but it’s somewhat common for modern vintage-inspired jewelry to feature rose-cut diamonds. Popularized in the 1700s, the rose cut features large triangular facets, a domed top, and a flat base. This gives the rose cut a glassy and luminous look, rather than a sparkly look.

Why Is Round The Most Popular Diamond Shape?

The round brilliant cut diamond gets its name from its impressive light performance. It’s the most brilliant of all the diamond shapes and that’s the main reason why the shape is so beloved. If you want maximum sparkle, you want a high-quality round brilliant cut diamond.

Another reason for the popularity of the round diamond shape is its style. Round diamonds have a classic, traditional style that’s considered timeless. Round diamond jewelry doesn’t go in and out of fashion. It’s simply always en vogue, which certainly contributes to the round diamond’s enduring popularity.

How to Buy a Round Diamond

Considering Cut

When you buy a round brilliant cut diamond, you want to prioritize diamond cut grade above all else. Diamond cut, one of the 4Cs of diamonds, is a grading of how well a diamond was cut, which affects its light performance. Cut quality is important for every shape, but it’s especially important for the round brilliant cut because this shape is all about shimmer. If a round diamond has been well cut, it will look beautifully bright, sparkly, and dazzling. However, if a round diamond is poorly cut, it will leak light, making it look dull, dim, lifeless, and smaller than it actually is.

The Gemological Institute of America (GIA) grades diamond cut on the following scale:

Excellent

Very Good

Good

Fair

Poor

In general, we don’t recommend going lower than Very Good for any type of round-cut diamond jewelry. If you’re buying a center diamond for an important piece of jewelry, like a round cut diamond engagement ring, you may want to consider picking a diamond with an Excellent cut if your budget allows. If not, a Very Good cut round diamond should still look beautifully brilliant. Good cut diamonds, on the other hand, are usually much less bright compared to Very Good cut diamonds. We don’t recommend Good, Fair, or Poor cut grades for round brilliant cut diamonds.

Considering Color

Diamond color grade is a grading of how colorless a diamond is. Diamonds can be completely colorless or they may have a yellow tint. Diamond color is graded on a letter scale that goes from D (completely colorless) to Z (light yellow). The various letters fall into different categories:

Colorless: D to F

Near Colorless: G to J

Faint: K to M

Very Light: N to R

Light: S to Z

So, do you need to pay a premium for a D grade colorless diamond to get a beautiful round diamond? Probably not, but it all depends on how important color is to you. It can be very hard to tell the difference between D and F diamonds, and G and H diamonds will also look colorless to most people. That’s why G and H color diamonds are often recommended as good budget picks. But, at the end of the day, the right color grade for you is all about personal preference and how you perceive color. Some people are hyper-aware of tiny color differences, while others can hardly tell the difference between a D color diamond and an H color diamond.

In addition to color grade, there are two finer details you should consider that affect diamond color: diamond fluorescence and the precious metal your diamond will be set in.

Diamond fluorescence, a glow that may appear in UV light, can affect diamond color in either a good or a bad way. Fluorescence is something that will be noted on a diamond’s grading report. It appears in around a third of all diamonds and it can range from faint to strong.

Around 99% of the time, diamond fluorescence is blue. Blue fluorescence can be either a good thing or a bad thing. Strong blue fluorescence is generally undesirable since it usually makes a diamond look cloudy. But a medium blue fluorescence can make a faintly yellow diamond look whiter, which can work to your advantage. However, any fluorescence can make a colorless diamond look hazy. If you’re paying more for a colorless diamond, you probably want to avoid fluorescence altogether.

The precious metal you set your round diamond in won’t change its color, but it can change your perception of its color. For example, if you have a faintly yellow K grade diamond and you put it in a white gold or platinum setting, your setting could make your diamond look very yellow in comparison. On the other hand, if you put a faintly yellow diamond in a rose gold or yellow gold setting, the warmth of your setting could mask a bit of color. A tint of color can be much harder to spot in a warm, richly colored setting. Alternatively, a rose gold or yellow gold setting can actually make a colorless diamond look a bit yellow due to light reflection. Say you have a D-color loose diamond that looks perfectly colorless on its own. If you put it in a yellow gold or rose gold setting, it will reflect some of the setting’s color, making it look a bit yellow. Some jewelers would consider putting a colorless diamond in a yellow or rose gold setting a bit of a waste.

In general, understanding fluorescence and knowing the color of your precious metal can help you pick the diamond color grade that’s right for you. Think about how much you care about color, how fluorescence could affect your diamond’s color, and how different color grades may look in your chosen precious metal, then decide on your color grade accordingly.

Considering Clarity

When you’re shopping for a round-cut diamond, you can usually be extremely flexible with clarity grade. Diamond clarity is a grading of how flawless a diamond is, internally and externally. But round brilliant cut diamonds have many tiny facets that reflect light and make it hard to see inside the diamond. This makes it considerably more challenging to spot flaws on a round brilliant diamond.

Diamond clarity is graded as follows:

Flawless (FL)

Internally Flawless (IF)

Very, Very Slightly Included (VVS1 and VVS2)

Very Slightly Included (VS1 and VS2)

Slightly Included (SI1 and SI2)

Included (I1, I2, and I3)

Generally speaking, an eye-clean diamond (this means it doesn’t have flaws that can be seen with the naked eye) is what most people want. For a round brilliant diamond, it’s possible to go as low as SI2 and get a flawless-looking eye-clean diamond. And it’s not particularly hard to find an eye-clean SI1 grade round diamond. So, if you can find an eye-clean diamond in the SI range, you don’t necessarily need to spend more for VS2 clarity or higher. If two diamonds are both eye-clean, they’ll look equally flawless regardless of their clarity grade. If you want to spend more for a more technically perfect diamond, however, you can certainly do so.

One thing to note about looking for an eye-clean diamond is that this is not something that will be on a diamond’s grading report. And it isn’t something that will necessarily be noted on an online listing. If you want to be more flexible with your diamond clarity grade, you should check and see whether or not the diamond is eye-clean by looking at it personally.

Considering Carat Weight

For most people, carat weight is all about budget. Higher carat diamonds are more expensive and people usually get the highest carat weight they can afford. We recommend thinking about what you want for your round diamond’s cut, color, and clarity, then considering carat weight. This will help you easily pick out a round diamond with the quality you want.

FAQ About Round Diamonds

Q: Is it true that round diamonds are more expensive than other diamond shapes?

A: Yes, round diamonds are more expensive than any other diamond shape. A round diamond can cost over 30% more than a fancy-shaped diamond with comparable qualities.

Q: Why are round diamonds more expensive?

A: Part of the reason round diamonds are more expensive than other diamond shapes is their immense popularity. Because so many people want round diamonds, people in the diamond industry charge more for them. However, popularity isn’t the only reason for higher round diamond prices. Round diamonds are more expensive to create. When diamond cutters take a rough diamond and cut it into a shape, they’ll always experience some rough diamond waste. Yet, cutting a round shape leads to more rough diamond waste than cutting any other shape, which makes the raw cost of creating a round diamond higher. On top of that, it takes a tremendous amount of skill to cut a high-quality round diamond, which also contributes to higher manufacturing costs.

Q: How much do round diamonds cost?

A: Round diamond prices can be dramatically different depending on the specific diamond’s carat weight and qualities. A one-carat diamond could cost anywhere from $2,000 to $18,000.

Q: Which fancy-shaped diamonds are similar to round diamonds?

A: If you like the look of round diamonds but don’t like their higher price tags, you could explore the idea of getting a fancy-shaped diamond with a similar style. Our top recommendations would be cushion cut diamonds, which are square-shaped diamonds with rounded edges, and oval-shaped diamonds. When they have a length-to-width ratio that’s approximately 1:1, cushion-cut diamonds can look very similar to round diamonds, especially once you set them in jewelry. Then, oval-shaped diamonds are always elongated, but their high brilliance and traditional look make them similar in style to round diamonds.

Q: Are round-cut diamonds good for engagement rings?

A: If you want your diamond engagement ring to have maximum sparkle and a classic style, a round-cut diamond is an excellent center stone choice. Round diamonds also look beautiful in every ring setting style, including halo, three stone, split shank, diamond band, and solitaire engagement rings. So, round diamonds are not only beautiful and classic but also versatile.

Q: What’s the best jewelry setting for a round diamond?

A: Round diamonds have a “blank slate” quality to them, allowing them to look spectacular in virtually every jewelry setting. With that said, round-cut diamonds look particularly incredible with certain setting styles. Round diamonds look amazing in solitaire settings, which provide a simple backdrop that lets the mesmerizing brilliance of the diamonds take full focus. Then, halo settings are seamlessly glamorous alongside round diamonds, pave diamond accented settings perfectly match the style of round diamonds, and engraved settings add lovely romance to the round diamond’s classic look.

Q: How big are the different carat sizes?

A: Every round diamond can have slightly different proportions, which can affect how large the diamond looks when viewed from above in jewelry. With that said, we can share average sizes for various carat weights to give you an idea of round diamond size. The table (the top) of a well-cut one-carat round diamond will measure around 6.5mm. A two-carat round diamond measures 8mm on average, while a three-carat round diamond measures around 9.1mm.

Q: Is round diamond certification important?

A: Yes, absolutely. No matter what diamond shape you’re buying, you should make sure your diamond comes with a diamond grading report from a reputable grading laboratory (like the GIA or AGS). A diamond grading report provides you with proof that your diamond has the qualities the jeweler or retailer you’re buying from says it does. If a diamond doesn’t come with a grading report, consider that a red flag.