The Round Brilliant diamond. Classic, bright, and timeless. Always a beautiful choice! Round cut diamonds are the most popular shape of all time, and produce the most brilliance of all diamond shapes. However, people regularly make three mistakes shopping for a round engagement ring that can ruin its beauty. And we’re not only talking about ignoring ideal round diamond proportions. Read on to learn what to focus on, what to ignore, and what to not pay a premium on.

Round Engagement Ring Mistake No. 1: Focusing on the Invisible

It is easy to get caught up in all the letters and numbers of diamond color and clarity. A website may tell you something, while a different jeweler tells you another. However, it pays to think for yourself. Can you actually see the differences in what they’re showing you? If you can’t see it, we’d recommend not prioritizing it.

4Cs scales for round diamond engagement rings

How to Properly Prioritize and Maximize Value

  • Look for “eye clean” stones, do not over-focus on VVS or flawless.
  • Focus on finding a stone that looks white to you, it doesn’t need to be technically “colorless.”

One of the first things couples learn about diamond grading is D-E-F “colorless” vs G-H-I-J “near colorless.” And then there is diamond clarity with VVS, VS, SI acronyms. Some say clarity is more important than color, while others say color is more important than clarity. But in reality, you don’t need a flawless stone. And you don’t need a colorless one either. Instead, focus on visually comparing color and clarity with your naked eye, and determine what you can actually see. If you cannot see it, then you do not need to prioritize it. Here is an example of clarity:

two round diamonds on gray background
The diamond on the left is a VVS1: a very rare, almost flawless clarity. The stone of the right is a VS2: a gem with a few inclusions that are not visible without magnification. In other words, without magnification, you cannot see inclusions in either one of these stones. In these two-carat diamonds, this equates to a $14,000 difference. Do you think it’s worth it?

Here’s an example of color:

round diamond color comparison
The diamond on the left is a D: the top color you can get. The diamond on the right is a G: the top of the “near colorless” tier. In these two-carat stones, there is a $9,000 difference between the D and the G. And, there is no distinct difference in these stones to the naked eye! Do you feel that is worth $9,000?

Moral of the story

In a Round engagement ring, don’t over-focus your attention on ultra-high color and clarity. A stone that looks white and doesn’t show eye-visible inclusions will look almost identical to a colorless, flawless stone. Instead, focus on cut – that is where you’ll get the biggest upgrade in look.

Round Engagement Ring Mistake No. 2: Not Focusing on Sparkle (Cut)

The cut of your Round engagement ring is not just its circular shape. Its “cut” also refers to how well the angles of your center stone align, how symmetrical all the facets are, and how well the stone is polished. These little differences are directly related to how much your stone sparkles. And, sparkle is the most important aspect of a diamond! The round brilliant was literally created to return the most light. As a result, they have the most sparkle to lose. So, not knowing the little differences in round diamond proportions is one of the biggest mistakes in choosing a round diamond.

round engagement ring cut chart

Ideal round diamond proportions create max sparkle

  • When a diamond is cut too shallowly, it can exhibit a “fisheye.” A fisheye occurs when the diamond is so shallow that the girdle (the very outer edge of the diamond) is reflected as a center ring in the diamond.
  • When a diamond is cut too deeply, a “nailhead” can occur. A nailhead is a dark area in the center of your gem where all your beautiful light is leaking out.

Nailheads and fisheyes occur when crown and pavilion angles are mismatched to an extreme extent. And, crown and pavilion “ideal” alignment makes certain round brilliants sparkle significantly more than the rest. So, understanding how these two angles are supposed to interact is very important. Because, without knowing what to look for, one can pay a premium for an “Excellent cut” stone, yet not get ideal round diamond proportions and max sparkle.

How to Get the Best Round Engagement Ring Sparkle (Cut)

Foolproof Option One: Learn Ideal Round Diamond Proportions

  • Only look at diamonds that fall within ideal round diamond proportion ranges.
  • Learn how angles work with one another so you can get max light return!

For max sparkle, each angle in your Round Engagement Ring must work together with the others. So, a Round diamond must fall within the below ranges AND its angles must align ideally.

chart of round diamond anatomy

IDEAL ROUND DIAMOND PROPORTIONS: RANGES

A bit frustratingly, GIA and the industry do not agree on what constitutes an “Ideal” Round Engagement Ring diamond. In fact, a quick Google search shows “Ideal” means something very different from one company to the next. That said, these parameters are a broad range that most jewelers will agree is a fair “ideal” starting point.

  • Table:                      55%-60%
  • Depth:                     58% to 63%
  • Pavilion Angle:     40.6 to 41.8
  • Crown Angle:        31.5 to 36.5
  • Girdle:                    Thin to Sl. Thick
  • Culet:                      None to Small
  • Polish:                    VG-EX
  • Symmetry:             VG-EX

Choosing a diamond that falls within these parameters means that they are a great candidate for excellent sparkle – and they will not have a fisheye or a nailhead. GIA “Excellent” cut diamonds typically fall within these parameters (so that’s an easy way to start this journey). But that’s not the end. After you’ve selected a few candidates, then look at their angles (you’ll find them on the GIA Certificate)!

IDEAL ROUND DIAMOND PROPORTIONS: ANGLES

Pavilion angle: The “pavilion angle” is the angle of the bottom facets on your diamond, compared with its girdle (its outer diameter).

Crown angle: The “crown angle” is the angle of the top facets against the girdle.

How they work together: Crown and pavilion angles need to coordinate with one another to bounce light back out the top of the diamond, and not lose it through the side or bottom. Remember using a mirror to play with sunlight as a kid? You know how when you moved the mirror, the light reflection moved, too? Those are how diamond angles work.

Example of where crown and angle pavilions are on GIA Cert

TOLKOWSKY IDEAL ROUND DIAMOND PROPORTIONS

Tolkowsky ideal round diamond proportions reflect a 34.5 degree crown and a 40.8 degree pavilion result in the most sparkle. However, you don’t need these exact angles to max your sparkle – you just need his math. A good rule of thumb is for every 1.0 degrees steeper your crown, subtract 0.2 degrees from your pavilion (for example: 35.5 crown, 40.6 pavilion). Likewise, for every 1.0 degrees shallower your crown is, add 0.2 degrees to your pavilion (for example: 33.5 crown, 41.0 pavilion).

Pro Tip! Diamonds with nice black arrows, like the one on the left below, often have ideal proportions. Diamonds without any “contrast” (dark arrows) will not be as sparkly.

Ideal cut diamond vs not ideal cut side by side comparison

(left) Ideal cut Round diamond vs Not ideal cut Round (right)

Moral of the Story

You can do this! Set your diamond search parameters to exclude anything but “Excellent” cut Round diamonds, then also set your table to 55-60%, depth percentages to 58-62%, and of course, your budget! Then, pick out 2-3 stones that strike your fancy. Pull up the Diamond Certificate, and compare your pavilion and crown angles against Tolkowsky’s angles to confirm ideal round diamond proportions. High/low, low/high. You got this.

Foolproof Option Two: Request an ASET Image for your Round Engagement Ring

So, there’s also a less-involved way to compare your Round Engagement Ring’s light return, too. Some diamonds come with their own computer-checked light return analysis. These are called “ASET Images.” An ASET Image is a color-coded photo of the diamond that shows how a diamond returns light.

green and red star pattern on round diamond engagement ring
  • Blue – Opposite of what you would expect, light that reflects in a straight line back to your eye will actually appear as a shadow. This “contrast” (what makes the stone dance from dark to light) is marked in blue. You want some contrast, in a pleasing, regular pattern.
  • Red – What you really want in a great ASET Image is red. That’s the light that creates great sparkle (light return at 45-75 degrees). 
  • Green – Light that reflects to your far left or right makes less of an impact, and is marked in green (light return at 0-45 degrees).

Finally, and very importantly, you do not want much white or black. White or black (depending upon the background of the image) mean you’re losing light out the bottom of the stone, never to be seen again. Look at all that light loss in the “average” stone!!

Moral of the Story

Red, all day, every day. You also want well defined blue. Green should be minimal. If it looks like it has white or black polka dots, you’re missing some light.

Foolproof Option Three: Ask a gemologist!

Still feel a little overwhelmed? That’s where diamond experts come in. If you have questions about diamond proportions, ASET Images, or just want help choosing between stones, email our gemologist here. I’m a GIA Graduate Gemologist and an AGS cut aficionado, which means I live and breathe this stuff. Answering your questions would make my day!

Round Engagement Ring Mistake No. 3: Not Comparing Apples to Apples (Certification)

All the colors, clarities, and angles you just learned are only worth so much as the paper they are written on. In other words, you can’t know them without a credible Diamond Certificate. GIA, AGS, and GCAL certificates are exacting, and IGI certificates stand up for lab created diamonds. Other labs simply do not hold up. So, make sure you are comparing apples to apples. A GIA graded G color will look white. An EGL graded G color will show color. Finally, diamonds sold without certifications are typically not top quality stones (else they would have been sent for certification). And, most jewelers selling them don’t know any better than you do what angles the gem has. Did you know that jewelers do not need any diamond or gemstone education to open a shop?

A long time ago, I once heard a jeweler tell a customer, “buying a non-certified diamond is like getting a puppy without papers. It’s still a puppy.” To which the (smart) customer said, “if I ever buy a puppy worth thousands of dollars, I want papers.”

dog with round engagement ring in wooden box

How to Get the Round Engagement Ring You Pay For

  • Natural Diamonds: pick a GIA Certificate
  • Lab Diamonds: pick a IGI or GCAL Certificate

The key to making sure you get what you pay for – and that your investment is protected – is a credible diamond certification. A diamond certification is a lab report from an independent laboratory that lists the diamond’s color, clarity, and proportions. So, it’s not just your jeweler’s word, it’s the professional opinion of someone who doesn’t have a horse in the race. Here’s my really long-winded explanation of why I suggest GIA for Natural Diamonds, and why I suggest IGI or GCAL for Lab Diamonds. And here’s the recap:

1. Credible Certificates Level the Playing Field

Your jeweler knows diamonds. They’ve probably done this for years or decades. However, you’ve probably not made a life out of looking at the minute differences between diamonds. So, your jeweler has a bit of an upper hand in this scenario. A credible diamond certificate levels this playing field, because there’s no wiggle room or ability to stretch the truth with an independent diamond quality analysis. So, you both know exactly what the diamond is, and what to compare it against. Less credible certificates, such as EGL, are “upgraded” (meaning an H color stone could be “certified” as an F), giving that power back over to your jeweler (who knows about, and will use, the upgraded color). As a result, when you demand a credible diamond certificate like GIA or GCAL, you and your jeweler are on equal footing.

2. Credible Diamond Certificates Protect Your Investment

For Natural Diamonds, GIA does the strictest diamond grading out there. When a Natural diamond has a GIA certificate, you know the color, clarity, and all the diamond proportions are correct. For Lab Diamonds, GIA, IGI, and GCAL are the most credible. In comparison, labs like EGL can be upwards of 2 grades off. You’ve done this much work to understand everything – don’t let an upgraded report ruin things.

Moral of the Story

Your Round engagement ring is one of the most emotional (and expensive!) purchases you’ll make in your life. A credible diamond certificate ensures you get exactly what you bargained for, and also that your partner and your insurer know exactly what you have. A credible diamond certification also makes sure that your investment is protected in the event you want to upgrade or pass down your diamond to a beloved child – your diamond certificate proves its quality and value.

round engagement ring in white gold

7mm (about 1.3 carat) Round Lab Diamond Engagement Ring

Do You Have Questions?

No worries! Email me here and I’ll walk you through it. Chatting with me is free. And together, we’ll make sure you get the best Round engagement ring for your taste and budget.