Does Diamond Size Matter When Buying an Engagement Ring?

This page may contain affiliate links.

minute/s reading time

October 22

As a matter of fact, diamond size does matter. Perhaps it shouldn’t, but the reality is that it does. As a matter of fact, the first question that people usually ask when they first see a diamond engagement ring is: How Big Is It? In other words, they want to know the diamond carat weight.

With that in mind, you might just need to accept the fact that size matters. Sure, we’re also going to talk about the importance of Diamond Cut Quality and Optical Precision. After all, these factors control how visually pleasing the diamond will be. That’s because they control the balance of brilliance, dispersion and scintillation. At the same time, the proportions of the diamond will play an active role in our enjoyment.

That’s why keeping the crown angle of the diamond between the range of 34.3 – 34.8 degrees offset by a pavilion angle of 40.6 – 40.9 degrees will help to create a visually pleasing balance of brilliance (reflected white light) and dispersion (reflected colored light) or “fire”. But, sometimes, in the end, it really comes down to size and I have to set my own preferences aside. After all, it’s my job to help each client find the Biggest Bang for the Buck and that’s what this post is all about.

Diamond Size vs Carat Weight:

The challenge with focusing on size is that I firmly believe that sometimes less is more. Personally I would rather present somebody with a diamond which is slightly smaller, but which is cut so precisely that it screams “Look at me!” from across the room.

Nice Ice was built on this premise and our entire diamond selection process revolves around selecting diamonds for visual performance.  Now while it’s possible to find diamonds that perform quite nicely outside the realm of super ideal cut diamonds, the fact is that the odds of finding a beautiful diamond dramatically increase within a specified set of parameters:

Total depth between 59 – 61.8%
Table diameter between 53 – 58%
Crown angle between 34.3 – 35 degrees
Pavilion angle between 40.6 – 40.9 degrees
Girdle: thin to medium
Culet: GIA none or AGS pointed
Polish: GIA Excellent or AGS Ideal
Symmetry: GIA Excellent or AGS Ideal
Overall Cut Rating: GIA Excellent or AGS Ideal

This range of parameters does not guarantee that the diamond will perform to my expectations visually. However, it dramatically increases the odds that it will.

My preference for this center range of proportions is shared by Brian Gavin Diamonds. As a matter of fact, Brian Gavin is the only diamond cutter in the world who holds a patent for maximizing light performance in the modern round brilliant cut diamond.

We’re also going to consider diamonds from Blue Nile and James Allen even though they tend to focus on a slightly broader range of proportions.

Balancing Precision, Performance and Cost:

It’s pretty easy for most people to understand that higher levels of precision and increased performance cost money when it comes to things like automobiles, but it can be a challenge for people to relate that understanding to diamonds which are usually discussed in terms of Carat Weight, Color, Clarity and Cut… especially since the majority of jewelry stores market “Shape” as “Cut” in what I believe is a conscious attempt to distract consumers away from the importance of Diamond Cut Quality and Visual Performance.

The only place the term “Cut” is used to describe “Shape” in the diamond industry is at the jewelry sales counter and on those glossy 4C’s marketing pamphlets that are practically useless… in the backroom, the buying office and the cutting room floor, the term “Cut” always refers to the proportions of the diamond, the polish rating, the symmetry rating and the overall diamond cut quality.

Now that you have an accurate understanding of Diamond Cut Quality, it is easy to see that precision cut diamonds are going to cost more than diamonds of lesser cut quality… just as a high performance automobile is going to cost more than a standard four door sedan and is likely to be more fun to drive.

But why does it cost more to produce an ideal cut diamond than a diamond of lesser cut quality? For one thing, more diamond rough is lost during the production process… quite simply, when a diamond is cut to less desirable proportions more of the diamond rough is retained during the cutting process and thus the diamond cutter retains more weight and his efforts will yield a heavier, but less beautiful diamond.

This approach works quite well for the diamond cutter in terms of profits because the majority of diamond buyers are primarily focused on the carat weight of the diamond and not the visual performance.  Since diamond prices are tiered by carat weight, it makes considerable sense for a diamond cutter to produce a finished diamond with the heaviest carat weight possible.  In addition, more time is spent planning the cutting of the diamond and actually cutting an ideal cut diamond than a diamond of mediocre cut quality… it takes a master craftsman to produce an ideal cut diamond, but a relatively new apprentice can cut a diamond of standard quality.

And then there is the extra equipment required to plan the cutting and actually cut a diamond to ideal proportions… even the polishing wheels must be changed out more frequently and all of this costs money.

The Benefits of Buying Precision

So I’ve provided you with some insight as to why ideal cut diamonds cost more than diamonds of standard diamond cut quality, but I haven’t really explained the benefits of buying an ideal cut diamond and so you’re probably wondering why you should spend more of your hard earned money than you have to… quite simply, the visual performance of an ideal cut diamond is dramatically superior to that of most non-ideal cut diamonds.

If we were to compare diamond cut quality to the wattage rating of a light bulb, the amount of light exhibited by the average zero ideal cut diamond (as outlined by the parameters listed at the beginning of this article) would be in the range of 100 watts. The degree of brilliance, dispersion and scintillation will be blinding!

In contrast, as the proportions of the diamond become less precise, the degree of brilliance, dispersion and scintillation decreases. Consequently, the diamond cut quality can result in a price difference as high as 60% in the wholesale market. So the next time that a jeweler tells you that diamond cut quality is not an important factor, consider that he either he might not have a very good grasp on the market conditions of buying a diamond (unlikely) or he simply doesn’t want you to understand the factors that go into pricing a diamond.

Brian Gavin Signature diamond reviews, AGSL 104060183027 diamond sizeSo the diamond quest which is the inspiration for this blog post began with asking me to help him find the “best possible 1-carat diamond” in his price range of $4,500 – 5000.00 and indicated that he was struggling with the variances of color and clarity which were available within this price range.

As an experienced diamond buyer, my initial reaction was to advise the client that a one carat diamond in this price range was going to look like, uh, dog shit (which I’m 99% positive is a professional gemological term) because it’s either going to be really heavily included or really, really low on the color scale, like something in the range of brownish-yellow-lime-green.

And then I proceeded to suggest that he consider something a little smaller and a lot nicer like 0.838 carat, H color, VS-2 clarity puppy from Brian Gavin because personally, I’d rather purchase something a little smaller that is going to scream “look at me” from across the room with the understanding that I can always trade it in for an upgrade for a special anniversary when I have a little bit more money to spend than buying something which is going to look less than desirable just for the sake of saying “it’s a carat”.

I also suggested this 0.82 carat, H, VS-2 from James Allen which is not cut as precisely as the previous option mentioned from BGD, but which is going to be a whole lot nicer than a $4-5K one carat diamond of lower quality.  Going back to the Light Bulb analogy used above, this puppy is probably in the range of 90 watts.

Now, why am I suggesting diamonds in the 0.80 – 0.99 carat weight category when the client specifically asked for a 1-carat diamond?  Because the client might not be aware that there is a substantial increase in the Price Per Carat (PPC) of diamonds that occurs between the 0.99 – 1.00 carat marks.  In terms of size, the average ideal cut diamond produced to my preferred set of parameters outlined above will have an outside diameter around 6.5 mm which is about the same diameter as the eraser on a standard #2 pencil.

The outside diameter of an 0.80 carat diamond produced to the same specifications will be around 6.0 mm so there isn’t a huge difference in terms of how large the diamond will “face-up” however the difference in price will be substantial… so what I’m trying to do is help the client find the best possible looking diamond within the confines of his desired price range and not necessarily something in the range of 1-carat because ultimately I think this is how I can serve his needs best.

But maybe I’m wrong, after all, this isn’t my engagement ring, not my money… not my diamond quest, but he did come to me for my advice and over the years I’ve consistently focused on the visual performance and optical precision of diamonds during my selection process because my preference is for diamonds which are truly beautiful and vibrant.  But keeping with the initial statements made by the client asking me for help, let’s see what’s out there:

Using the diamond search engine from Brian Gavin Diamonds and limiting the selection criteria to Brian Gavin Select which are virtual diamonds that are not produced by Brian Gavin, but which fall within a slightly expanded range of parameters than those I stated towards the beginning of this article and “everything else” which is quite literally “everything else” listed for sale in the multiple listing service used by the trade to buy and sell diamonds worldwide, I found the following options within the desired price range:

Brian Gavin Select 1.01 carats, SI-1 clarity and I color with no fluorescence with an overall cut rating of GIA Excellent which is the highest rating available from the GIA for proportions, polish, and symmetry.  The diamond has a total depth of 61.6% with a table diameter of 59% and a crown angle of 34.0 degrees which is offset by a pavilion angle of 41.4 degrees with a medium to slightly thick, faceted girdle.

Now while I’m sure this is, ahem, “a very pretty diamond” it’s probably about 60 watts on the scale of visual performance that I operate from within.  And because of the slightly thick girdle and the extra depth in the pavilion (lower half) the outside diameter of the diamond averages 6.45 mm which is a little less than I expect a one-carat diamond to face-up and thus you’d be paying a premium for the carat weight, but ending up with the look of something in the ninety point range… so I’m not convinced this is a great option, but it does fall within the parameters specified by the client.

Next, I found this Brian Gavin Select diamond which is graded by the GIA as weighing 1.06 carats, SI-1 clarity, J color with no fluorescence with an overall cut rating of GIA Excellent.  Now this one is cut a little better with a total depth of 61.1 and a table diameter of 34.0 degrees offset by a pavilion angle of 40.6 degrees with a slightly thick girdle.

Now, this diamond is most likely quite pretty because the pavilion angle which controls the majority of light return is within my preferred range of 40.6 – 40.9 degrees and the slightly shallow crown angle is probably giving the diamond a fair amount of brilliance (reflected white light). However, the inclusions within the diamond sent a shudder down my spine because they consist of extensive twinning wisps, a feather (which I can live with), and a needle which is just a tiny diamond crystal that is shaped like a needle… and something called an “etch channel” which I’ve never heard of and frankly doesn’t sound good.

So imagine me sitting in front of my computer trying to shake the shudders off of me and I decide to wander over to James Allen Diamonds to see if I can find anything a little less scary. I find several options within the parameters specified by the client and this is the most interesting:

GIA graded 1.01 carat, SI-2 clarity, I color with no fluorescence, and an overall cut rating of GIA Excellent with a total depth of 60.1% and a table diameter of 58% with a crown angle of 32.5 degrees (SHALLOW, really shallow) with a pavilion depth of 41.0 degrees which in my opinion drops this puppy right into the MUTT category… but it’s a 1-carat that fits within the desired price range and it’s not too bad… it’s not too bad… are you paying attention?

All right well perhaps you’re beginning to realize why I usually don’t waste my time trying to find exceptionally pretty diamonds outside the realm of super ideal… there are too many options and it’s very rare that I ever find anything that doesn’t make me itch.  So now that I’ve spent about an hour sifting through the options over a carat on Brian Gavin and James Allen, I’m going to drop back down under the 1.00 carat mark and see what else seems interesting.  James Allen had four options available in the 0.90 – 0.99 carat range in their True Hearts collection and of those four, this one met my selection criteria in terms of proportions (the other four were cut beyond my personal preference):

James Allen True Hearts graded by the AGS as weighing 0.90 carats, VVS-2 clarity, J color with negligible fluorescence with an overall cut rating of AGS Ideal 0 which is the highest rating available from the AGS Laboratory for polish, symmetry, proportions and Light Performance.  The diamond has a total depth of 61.8% with a table diameter of 56.4% with a crown angle of 34.5 degrees offset by a pavilion angle of 40.7 degrees ~ NOW we’re talking!  This diamond should have a sparkling personality which is sure to please!  It would be great if we could trade a slightly lower clarity for a little better color, but that’s just not in the cards today in terms of what’s currently available within the James Allen True Hearts collection and I’m trying to find options within the 0.90 – 0.99 carat range to keep the outside diameter up, which averages 6.18 mm in this particular instance.

There was nothing available in the 0.90 – 0.99 carat range from Brian Gavin Diamonds at the time I wrote this article and nothing available from Infinity Diamonds.  Finally, I decided to approach this project from the perspective that I usually take when trying to find diamonds for my clients,

I shop for a diamond as if I were going to buy it for myself, tossing carat weight aside and focusing on visual performance while being aware of the clients budget… and for my money, I’d buy this 0.822 carat, VS-2 clarity, G color diamond from the Brian Gavin Signature Collection, it is graded by the AGS with an overall cut rating of AGS Ideal 0.

The average outside diameter is 6.05 mm and the diamond has a total depth of 60.9% with a table diameter of 57.1 with a crown angle of 34.6 degrees offset by a pavilion angle of 40.8 degrees with a thin to medium, faceted girdle.

The primary inclusions are tiny diamond crystals and a cloud of pinpoint size diamond crystals that were trapped within the larger diamond crystal as it formed.  The diamond exhibits a crisp and complete pattern of hearts and arrows so the optical precision is dead-on and Brian tells me that it’s drop-dead gorgeous.  Ladies & Gentlemen, we have a winner! Punch the winning lottery ticket and tell Brian to drop it in a setting.

About the Author

Dive deep into the glittering world of diamonds with Todd Gray, the CEO of Gray Matter Development, LLC. Todd has 35+ years of experience as a diamond buyer and trade consultant. He ghostwrites content for several online vendors and is an avid Freediver, currently exploring the Cenotes of Yucatan, Mexico. Dive into brilliance with Todd Gray!