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How You Should Actually Shop for a 3 Carat Diamond Ring

By Stephanie Dore

We get it. Size matters to you. And because it matters to you, it most definitely matters to us. We hear it time and time again, someone wants a 3 carat diamond ring and the first question is, “how much does a 3 carat diamond cost?” Well, darlings, you’re asking the wrong question. Think about it like buying a house, let’s say. You’re comparing a bunch of properties that are all the same square footage—but everything else is different. Different finishes, different neighborhoods, different layouts…and thus totally different prices. And those are the things that will determine if you’re happy living in that house for, say, ever. Well, you’re going to wear that engagement ring forever too, so here’s how you should actually shop for that stunner.

3 carat oval diamond ring paired with half carat eternity band and baguette channel band
The Harper No 2 with a 3 carat oval diamond center adds flawless elongation when stacked with alternating bands.

Are you fancy, now?

This comes as a shock to many diamond newbies, especially since it’s not one of the 4Cs, but the shape of a diamond plays a pretty major role in its price. As the most popular (and available) diamond shape, a round diamond (no matter the size) will cost you about 20% more than any fancy shape. What’s a fancy shape, you ask? That’s the easy question: anything other than round. 

Fancy shapes can not only save you dollar bills but some even look bigger! Take an oval for instance. A 3 carat oval diamond ring is going to look about 20% larger than a 3 carat round diamond simply because of its shape (and its cut, really). Because it’s elongated and cut shallower in the pavilion, an oval’s weight is more spread out, giving you more look for your money. Now…an Asscher on the other hand is going to look a little smaller than the same weight round. The visual size of a diamond is all about the shape and proportions (the length to width ratio and overall depth). Here’s more:


The super standard of the industry, round diamonds with an excellent or ideal cut grade won’t vary much. If you go lower on cut grade (not our recommendation) then you risk getting a diamond that hides its weight in a thicker girdle or deep pavilion, meaning it’ll look smaller from the top view—which is how everyone’s going to see it. An ideal cut 3 carat round diamond should be about 9.3mm in diameter. 


Because a princess cut diamond is most similar to a rough diamond’s natural octahedral shape, they do tend to offer some savings in price (you know, less wasted diamond and all…). But they’re also the second most popular shape, so it’s not that much savings. Also, they tend to be cut a bit deeper, so their diameters across the top may make them look a little under-sized for their weight. An ideal cut, 3 carat square princess cut will be about 8mm in length x 8mm in width.


Like we said, with oval diamonds, you can get a big look for your little buck (ok, maybe little is a reach). But, these shallow-cut diamonds with tons of spread also have all the brilliance of a classic round diamond. What to watch out for? Bow ties. An ideal cut 3 carat oval diamond ring will be about 11.5mm long x 7.5mm wide.

An elongated emerald cut will give you maximum length for carat weight.


It’s not easy to find a really well cut emerald cut diamond, but totally worth it if you do because this elongated, super sophisticated shape will give you plenty of rock to admire. Just be sure not to skimp on clarity grade because the emerald’s long, open facets are like big windows for inclusions to show through. An ideal cut 3 carat emerald will be about 9.5mm long x 7mm wide.


Similar to emeralds, the step-cut faceting of an Asscher cut means you probably don’t want to sacrifice on clarity. Unlike emerald, though, Asschers tend to run deep and small like princess cuts. They might look a little under-size for their weight. The trade off? Mesmerizing facets that with a pinwheel pattern that you can get lost in for daaaaays. An ideal cut 3 carat Asscher diamond will be about 8.1mm in length x 8.1mm in width.

custom frank darling asscher five stone diamond engagement ring
Similar to cushions, it is extremely important to pay attention to the table size of an Asscher cut.
frank darling radiant yellow gold bezel setting
Radiant cuts are fantastic length-maximizing hybrids!


These mixed-cut diamonds are gorgeous. But they’re not big. Or at least they don’t look it. Typically cut deeper, with smaller face-up measurements, you can find some more elongated shapes that will help you maximize the size appearance. Just make sure they’re not hiding weight in a thick girdle (so you’re not paying for what you can’t see). A 3 carat ideal cut radiant diamond will be about 8.5mm in length x 7.5mm width.


It’s harder to determine what you’re getting with a cushion cut diamond because each one is totally unique. Elongated cushions can give you tons of spread and a crushed-ice look that is totally on-trend right now. While squared cushions tend to be cut a bit deeper and therefore have a smaller overall look for their weight. Aim for a depth percentage under 70%, and a table under 70% for best results. An ideal cut 3 carat cushion diamond will be about 9mm long x 8mm wide.

Custom Frank Darling Harper no 4  cushion engagement ring in platinum and yellow gold
Cushions can’t be taken at face value, but you definitely want to maximize the face of the diamond. Make sure to pay attention to table measurements when shopping for a cushion!


Marquise cut diamonds, like ovals, have a super elongated form and tons of spread. Cut pretty shallow, their weight is more visible face up than with other shapes. But also similar to ovals, they can have those annoying bow ties through their bellies, or super thin points that hold color (and are more prone to breaking). We love them turned horizontally for lots of finger coverage! An ideal cut 3 carat marquise diamond will be about 14mm long x 7mm across.

Custom Frank Darling Harper pear cut diamond solitaire engagement ring in platinum
Rotate your pear sideways
for a modern, unique look


Because they’re kind of a cross between a round and a marquise diamond, a pear cut diamond will be somewhere in the middle. Deeper under the rounded end and shallower under the point, an ideal cut 3 carat pear shaped diamond will measure about 12.5mm long x 8mm wide, giving you the best of both worlds.

Top of the Class

You guessed it. We can’t have a discussion about diamond pricing without all the Cs showing up. So what’s next? Cut. Truly always the most important of the Cs, cut grade is what determines your diamond’s sparkle. I mean, you could get a 3 carat diamond ring with a low cut grade but…it’s going to look like a big, dull hunk of rock. Kind of missing the point, right? While only round diamonds have actual cut grades, the proportions of fancy shapes can tell you a lot. Our two cents, though? Get your eyes on it! The best way to know if your diamond has the shape and sparkle you’re after? Seeing it. BTW: we can help with that.

Get way more size for your buck with a champagne diamond. Or, add a halo for some extra width!

Thank You, Next

Don’t think we’re letting you go without a little word on the importance of color and clarity—especially when it comes to purchasing a sizable diamond. Because, yes, the bigger the diamond, the more color it can hold. But going a bit lower in color (say…champagne hued) can get you a warm, sparkling glass of…oh sorry got distracted. But really, a lot of brilliance for less. But also bigger facets also mean bigger windows to see inclusions through. We always recommend starting with something in the middle of the road, say VS1 – VS2, then toggling around until you reach your target price. Again, getting a photo or video of your actual diamond will help you determine how it looks. 

Saving Private Diamond

If you’re looking to get the most size for your money (who doesn’t love that?) then there are a few super easy ways to go about that. First? Buy shy. Little trick of the trade—diamond prices jump at the whole carat mark. Which means you’ll pay a lot more for a diamond that’s exactly 3 carats than one that’s 2.9 carats…and you probably won’t be able to see the difference. If you’re cool with it, shop in the 2.7-2.9 carat range for some serious savings. 

Your Type or Mine?

Lab grown or Earth mined, the rocks don’t lose their…ok that doesn’t rhyme at all. But really, diamond type is a major price differentiator. In general, lab grown diamonds will cost 40-50% less than a comparable mined diamond. We also love moissanite as a diamond alternative for its superb sparkle, durability, and low price tag. Or go all out and shop colored diamonds or gemstones to really open up your options!

frank darling custom radiant diamond cut engagement ring
Lab or Natural? Both will look beautiful! Just work with what works for your budget and preferences.
frank darling oval diamond engagement ring with double claw prongs in yellow gold
Best way to make your 3 carat stunner the main character? Set it on a solitaire.

Speaking of Possibilities…

When it comes to the best engagement ring settings for a 3 carat diamond, we suggest keeping it minimal. You want the diamond to be the center of attention after all, right? Nothing pops more than a 3 carat stone on a barely-there, 1.5mm band. Also, keep it vertical if you’re going for a fancy, elongated shape. While east-west settings are trending, they’re better suited to 1 or 2 carat diamonds. A 3 carat diamond ring needs that added finger length to really shine.

Want some extra sparkle? If you’re considering an emerald or Asscher, vertical baguette or trapezoid side stones can enhance the hall of mirrors effect. Or try a hidden halo that shines from the side without distracting or adding too much fuss from the top view. Have something specific in mind? Take the ring quiz to get a free sketch!

Ready to Find Your Dream Diamond?

If you’re not sure on size, order a whole flight! We’ll send you four cubic zirconia “diamonds,” in your choice of size and shape, for free! Click here to get started. Check out our diamond search where you can view 360-degree images of more than 10,000 diamonds and don’t forget to zoom out (because size can be deceiving), or book an appointment at our New York salon to view certified lab-grown and natural diamonds in person. Not finding what you’re looking for? Email us with what you’re looking for at and we’ll curate a list of 5-7 exclusive stones that are just right for you.

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