Oval vs. Round Diamonds:
The Definitive Comparison

The sparkle of a diamond is that unmistakable flash of fire, brilliance, and scintillation emanating from the stone with every movement. The round cut diamond has the most sparkle of any diamond shape or cut due to its faceting structure and concentrated shape.

Round and oval diamonds both fall into the category of brilliant cut diamonds. Brilliant cut diamonds are so called because they are cut in such a way as to maximize the diamond’s brilliance. With 58 facets, round diamonds deliver fantastic white light reflection. Oval diamonds are typically cut with 57-58 facets, so have the potential to deliver just as much sparkle as a round diamond.                                                                                                                                                                                                                

To caption this concept of brilliance, diamond laboratories such as the GIA have come up with a grading scale to rate the brilliance of a diamond. The cut of a diamond is graded on a scale of Excellent to Poor, and this is done with a strict formula that incorporates the various measurements of a diamond (table & depth percentage, crown & pavilion angles). In other words, there is theoretically a range of proportions that provide for excellent light return. In addition to excellent symmetry, an ideally proportioned diamond should not be cut too flat nor too deep; somewhere in the middle is the sweet spot. While this formula is not perfect, it does a pretty good job at separating out all the poorly cut diamonds, and is a good tool to have when shopping for a round diamond. Unfortunately this Cut grade is not given to oval shape diamonds, and there's a good reason for this omission.  

In reality, it is very difficult to assign a ‘light return’ grade to an oval shape because every oval is so different. The long and skinny ovals must have a very different light-return profile than a short and round oval. Perhaps by incorporating the length to width ratio as a new factor to consider, the labs can begin to ascertain the light performance of a diamond based on its proportions. Until then, the ability to compare brilliance between oval shape diamonds based on measurements remains elusive, and the best way to determine cut is to compare multiple diamonds and choose the one that looks best to you.

The brilliance of both the oval and round cut diamond make each a perfect candidate for masking inclusions and blemishes. Because of their faceting, each does a good job of hiding inclusions and blemishes well near the sides of the stone, especially ovals. You would just want to be sure the inclusions aren’t too close to the girdle as this makes the diamond more prone to chipping with continued wear.

Ovals have a specific imperfection all their own that requires special attention called the bow-tie effect. This term describes a visible shadow across the diamond’s center width that appears to resemble a bow tie. The bow-tie effect can vary in degrees of severity and will only show from a direct face-up angle. So for ovals, it’s important to view the diamond in person to truly discern if a bow tie is apparent and to what degree.

While you can never avoid the bow-tie effect entirely with ovals, we choose the ones that look good with minimal bow-tie, and the end result is always a stunning design. Our advice to clients is to avoid the oval diamonds with obvious bow-tie, but not to get too hung up on this feature. In the end, a pretty oval will make for a gorgeous ring.

To illustrate this effect, we can look at two ovals side by side. On the left side of the image next to this paragraph is a nearly perfect stone - we’ve rarely seen anything nicer - but if you look really hard, there is still a slight bow-tie. On the right is a more common, still beautiful, oval with its signature bow-tie effect more noticeable in the middle.

When it comes to the size difference between oval and round diamonds, there are a few factors involved that give an advantage to ovals appearing larger. Because of its elongated shape and weight distribution toward the top of the stone, ovals will appear larger than round diamonds of the same carat weight.

This fact is backed up by the overall surface area of the diamond on display. Ovals come out about 10% bigger than round cut diamonds of a similar carat weight. Also since an oval will always have a longer length and a shorter width for its ratio measurement, most people intuitively look at the length of the oval and subconsciously determine the oval’s size with that measurement instead of the width.

Round diamonds are more uniform because they will always be the same shape. They may differ in carat size, but they are only ever round.

An oval diamond, on the other hand, will come in a variety of shapes and sizes depending on its length to width ratio. Oval diamonds can range in length to width ratio from 1.28 to 1.70. An elongated oval will appear thin and long and have a length to width ratio above 1.5. A more rounded oval will appear wider and fuller and sit closer to the 1.3 ratio. You will find that most oval diamonds have a 1.34 to 1.42 ratio.

To illustrate, here are two oval rings with different length to width ratios. The one to the left has a 1.30 length to width ratio; you’ll notice that it’s more rounded in appearance. The one to the right has a 1.52 length to width ratio.

Because of this spectrum, one oval diamond to the next will likely look different in shape whereas a round cut never will. Depending on the look you’re trying to achieve, oval diamonds will give you many more choices to design a ring that is that much more personal and unique, especially since they can be set vertically or horizontally in a ring.

Round diamonds are the most abundant diamond cut available, but for good reason. They are timeless and create the most stunning, sparkly engagement rings. There will always be more options of round cut diamonds in a wide range of quality.

Oval diamonds are much less prominent due to a lower demand. So, they’re actually rarer than round cut diamonds. However, since ovals will vary so much in shape, and round cut diamonds won’t, it may be much harder to find an oval cut diamond to fit your desired specifications.

Due to their high demand, round cut diamonds are generally 10% to as much as 30% more expensive than oval diamonds in a side-by-side exact quality comparison. This cost difference is mostly due to the much higher demand of round diamonds. However, how the two shapes are cut also plays a part. Cutting a diamond into a perfectly round shape results in up to 40% of the diamond rough being wasted. This makes round cut diamonds more expensive to produce.

Round diamonds also have a lot of competition because every dealer has the majority of their stock in round, which makes the margins razor thin. Rounds are also commoditized, especially since they are graded on cut. There’s probably slightly more market inefficiency with ovals since they can’t be easily compared based on the lab report alone, and the highest quality cut stones will get priced at a premium. In the end, price comparison between the two shapes is very difficult, and probably not incredibly productive. Our advice is to choose the shape that you like most, and not let price drive your decision.

Color is going to be quite different in comparison between an oval diamond and a round diamond. Oval diamonds are, on average, visually one to two color grades lower than round diamonds. What we mean by this is that in terms of color alone, the average G color oval will look like an average H or I color round.

This occurs for a couple of reasons. Firstly, round diamonds hide color well because of their brilliance, so a lower color grade may still appear quite white. And secondly, oval diamonds tend to show more color because of their shallower cut, so they’ll need a higher color grade to still appear white to the naked eye. Knowing these factors, you can play with the other diamond 4Cs to determine what will work best for your preferences.

When it comes to designing an oval versus a round diamond ring, the best advice is to consider how the stone will look on your hand. While oval and round diamonds look great on all types of hands, there are some for whom the attributes of these specific stones can be exceptional.

An oval diamond, whether more elongated or wider, will have the visual effect of lengthening the finger. This could be a lovely match for those with fuller hands or shorter fingers. A round diamond will enhance the fullness of a finger because of its equal proportions, so is a very appealing, balancing look for anyone with more slender fingers.

From a jeweler’s design perspective, round diamonds are incredibly easy to work with and are well-suited for every type of setting. That’s not to say that oval diamonds are difficult to work with, but for certain designs, an oval stone wouldn’t work, as with our Sundara. Our Pembroke is another examples where most clients feel a round stone looks better than an oval: