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The Ultimate Guide to the Round Brilliant Cut Diamond

By Stephanie Dore

Pretty much guaranteed to out-sparkle the competition, the round brilliant cut diamond is pretty fool-proof. Except that’s it’s not. While it’s easy to find a pretty one — they make up more than 75% of diamond sales — it’s also pretty easy to go wrong. Which will leave you with a big (or small) dull rock on your finger. Not to worry, darling, we’re here to make sure that doesn’t happen. Here’s your go-to guide to finding the most brilliant round diamond for your dollar.

Picture Perfect

When we say the modern round brilliant cut diamond has been exhaustively engineered to sparkle perfectly, we’re not even joking. For real, y’all. What started as rough turned into old mine cuts, hewn by hand to glimmer in the candlelight, and ended up as today’s laser-cut masterpieces cut to the highest specs. This is made them quite popular. And also pretty pricey. While round diamonds are the most available in the market, they’re also the most expensive. A round diamond (with comparable 4Cs to any other shape) will cost you 25% more. So make sure you’re putting your money where it counts.

Frank Darling custom round diamond bezel engagement ring
Want to satisfy your inner perfectionist? There is no better choice than the round brilliant.
frank darling round brilliant cut pavé diamond ring with sapphire accents
With rounds, brilliance is key.

Sure Round Brilliant Cut Bet

Where does it count? Cut. Cut. Cut. Above all other Cs, and most especially when it comes to round diamonds, cut grade is the most important. It’s the C that will play the biggest part in determining the brilliance and beauty of your diamond. And round diamonds are the only shape that has an industry standard grading system, so you know it’s important. A diamond’s cut grade takes into consideration:

  1. The diamond’s face-up appearance based on brightness, fire and scintillation
  2. The diamond’s proportions
  3. The craftsmanship, symmetry, and polish of the diamond’s facets

That Sparkle in Your Eye

What you call “sparkle” is really a diamond’s brightness, fire, and scintillation. Brightness is the white light you see returned to your eye. Fire are those rainbow flashes. And scintillation is that sparkly pattern of light and dark you get when you move the diamond around. This is all to say that how well a diamond is cut determines how well it bounces light around and back to your eye, resulting in, yes, sparkle.

frank darling custom compass point prong round brilliant diamond ring
Two-tone rings are a great way to add intrigue and max out the brilliance of your round diamond.
Frank darling custom 5 carat round diamond ring stack
The bigger you go, the more important your diamond’s proportions are!

Measuring Twice

A diamond’s proportions — the crown and pavilion angles, the size and placement of its facets — are pretty major too. Cut too shallow or too deep and light will just leak right out of the diamond instead of sparkling back to your eye. Remember, all those tiny facets act like mirrors, bouncing light around. If any of them are out of line, then light goes somewhere else. But there’s no single set of perfect proportions, and diamonds with different proportions can get the same cut grade. This is because all the different angles can add up to the same visual effect.

What’s Your Angle

So, if there’s no perfect set of proportions, it can be tough to narrow down what you’re looking for — but not so much for round diamonds, because they have cut grades. That means someone has already done the work for you! But here’s the stuff that gets measured

Now, if you’re comparing two diamonds with the same cut grade, you can use, say, the table percentage or depth percentage to further refine your assessment. But the cut grade takes all of that into account and will give you a better overall picture of how pretty your diamond is.

Polished Perfection

When it comes to a diamond’s finish — it’s symmetry and polish — you don’t want to skimp. It may seem like an extra, but it’s very important to your diamond’s beauty. Symmetry is how well all those little facets are aligned and perfected, and polish is just that. Are the surfaces smooth, with no trace of the cutting process. A little misalignment or poor polish can result in, well, a not so pretty stone. Now, if you’re buying a high cut grade, you’re likely going to have high symmetry and polish, but it doesn’t hurt to double check!

frank darling round diamond platinum solitaire ring
Want to let the diamond be the star? Set it in a classic prong solitaire.

Color Me Good

Color is the second most visible of the 4Cs to the naked eye, so it’s up next! Yes, that’s right, your eye can see minor color differences more noticeably than those inclusions, no matter how much you think otherwise. Color is graded not on the presence of color but the relative absence of it. So higher color grades (D, E, F) are “colorless” and then it goes on to “near colorless” (G, H, I, J), and so on. A well-cut round brilliant diamond can actually hide a little bit of body color, so you might go lower than you think in the range before you start noticing color. But many retailers will keep their inventory in that range and nothing below because I-J is where many folks start to see that warmth in a diamond. But guess what, the standard color range goes all the way to Z before it becomes what we call a “fancy color” diamond, so there’s a lot more room to play! Why do color grades start at D? Well, because back in the day before GIA set the modern standard, diamond colors were referred to with A, B, C, so it’s just easier not to get them confused.

Frank Darling custom split shank round brilliant diamond engagement ring
Yellow gold will bring color into your diamond anyway, so you may as well go warm!

Warm it Up

Now, we mentioned a whole range of colors, from K-Z, that really don’t get enough credit, folks. These warm, often yellow or brown tinted, stones offer both a unique look and a good bargain. We’ve been absolutely loving a warm colored diamond set in yellow gold for a super toasty, sunshiney, champagne-y feel. You can showcase a single stone, use them as contrasting accent stones to a colorless center, create a fun multi-hued cluster, or even an ombre effect that’s super timeless. And they’ll save you a bunch of cash over higher colored stones. What’s not to love about that?

Forget About Flawless

When it comes to diamond clarity, darling, please stop obsessing over the idea of flawless. Unless it’s truly your highest of high priorities and you’re flush with dollars you’re not worried about wasting, it’s just that — a waste. How so? Well, you’re basically spending money on something you’re never going to see. And that’s just not a good look. What’s a better look? An eye-clean diamond, darling. Eye clean is a common industry term that basically means the diamond will appear inclusion-free to the untrained, unaided eye at a normal viewing distance. Like, say, holding your hand out to gaze lovingly at your new jewelry. Not holding your ring up to your eyeball and squinting real hard. Eye clean is where you’ll strike the perfect balance between looks and price tag.

Round Brilliant Disguise

Now, the truly awesome thing about round diamonds is that their super-perfected brilliant cut works a bit like a killer Halloween costume. It’s the perfect disguise for not only a little bit of warm body color but also plenty of clarity characteristics. Yep, all that sparkle actually hides inclusions in round diamonds, so you can usually go a bit lower than you might think — even in the SI1-SI2 range — and still find an eye-clean diamond. The only way to know for sure, however, is to get your eyes on the prize. Yes, look at a diamond clarity plot (like a little map of inclusions) on your diamond’s certificate if it’s available (anything over 1 carat should have a full plot), but we strongly recommend getting photos and video of your stone as well.

Frank Darling round brilliant cut cluster diamond engagement ring
Love the classic, but not the boring? Customize your setting to elevate your round brilliant.
Frank Darling split shank round brilliant cut diamond engagement ring
Statement rings come in all shapes, but there’s something particularly brilliant about a round.

Size Doesn’t Matter

Look, most people are obsessed with size in some form or another, but to be frank, darling, it’s the least of the 4Cs you should worry about. Why? Well, because it really doesn’t matter. Yes, carat weight plays a major part in the pricing of a diamond, which we’ll get to in a sec, but other than that carat weight can be kind of an afterthought. It doesn’t determine beauty. It’s just, well, size. And not even that! Carat isn’t size, in fact, it’s the physical weight of the diamond. So you could have a poorly cut diamond with icky weight distribution that is higher carat weight but not so fun to look at. This is why you should put your money elsewhere. 

Sizing for Savings

Now, not everyone wants a big diamond. Sometimes a smaller diamond is what folks are after. But regardless of what size you’re looking for, you should know how to save money on it. Two ways: First, like we’ve been saying, is spending your money on a higher cut grade. Because, yes, diamond sparkle and brilliance can actually make your stone look a little bigger than its weight. And second, buy shy. Diamond prices jump exponentially at whole carat marks (1 carat, 2 carat, what have you), so buying something just below these weights can save you serious cash and you won’t even notice the difference. In fact, a ideal cut, .90 carat round brilliant diamond can look bigger than a good cut 1 carat any day of the week.

Can I Have Some More, Please?

Yes, yes you can. If you’re money-minded (aren’t we all?) or just looking for alternatives to a mined diamond (hello, you eco-conscious darlings), we’ve got your back. Lab created diamonds are a great, sustainable alternative to mined diamonds that can save you basically half the cost. And they’re still real diamonds! Yes, they’re real — chemically, optically, physically the same as a mined diamond. Just made in a lab. With science! That means exactly the same look for way less. Lab diamonds do have some slightly different clarity characteristics, but overall will have exactly the same grading determinations as a regular ol’ round brilliant cut, so you already know what to look for!

Round diamonds love side stones, especially funky ones like these black diamond accents!
Frank Darling round brilliant cut diamond ring with baguettes
The bigger the better when it comes to rounds!

More Money, No Problems

Want to save yourself even more? Moissanite — another type of gemstone altogether — also offers a fantastic alternative. Moissanite has, historically, been known for simulating the look of a diamond but is quickly gaining popularity as a gemstone preference in its own right, and we’re all aboard. Does it look just like diamond? Nope. But pretty similar. In fact, it has even more fiery rainbow sparkle (rather than straight up white sparkle) than a diamond, and some people totally love that. Did we mention it’s also a fraction of the cost? Well, it is. And just like lab created diamonds, moissanite is created in a lab and thus with either of these if you’re looking for something really specific, you can basically have it custom created. Bonus!

This Round’s On Us

Ready to find your dream round diamond? Check out our diamond search where you can view 360-degree images of more than 10,000 GIA and IGI certified lab grown and natural diamonds and don’t forget to zoom out (because size can be deceiving), or book a virtual or offline appointment at our New York studio to view diamonds in person. 

Not finding what you’re looking for? Email us with what you’re looking for at We’ll curate a list of 5-7 exclusive stones that are just right for you.

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