Ideal Proportions for a Round Brilliant Cut Diamond
Marcel Tolkowsky revolutionized the world of round brilliant diamonds in 1919 when he published his landmark book titled “Diamond Design“. In his book, he wrote about a set of proportions that would yield in a diamond with maximum beauty, fire and scintillation based on mathematical calculations. Ever since the epic publication, Tolkowsky’s findings were widely applied in diamond polishing by cutters around the world.
Marcel Tolkowsky’s ideal proportions for a round brilliant diamond.
In more modern times, much has changed as Tolkowsky’s groundbreaking discoveries were further developed upon. With the help of specialized studies and technological advancement, researchers from GIA & AGS had published scientific journals that changed the way we polish and buy diamonds.
One of the major breakthroughs made was the discovery that ideal cut diamonds do not have to follow a single set of proportions as set forth in Tolkowsky’s original dissertation. In fact, a diamond could be polished within a range of proportions and it would still display ideal optics.
General Proportions For Round Brilliant Cut From Tolkowsky
| Table % | 52.4% to 57.5% |
| Depth % | 56.88% to 63.92% |
| Crown Angle | 33.7° to 35.8° |
| Pavilion Angle | 40.2° to 41.25° |
| Girdle Thickness | Thin – Medium |
| Culet Size | None |
Source: The Ideal Cut: A Consumer’s Guide.
*Note: The above historical table should be used as a reference only. With modern day research, the Tolkowsky proportions have been further refined. If you are looking for a diamond that exhibits superior brilliance and sparkle, scroll down to use MY proven table of ideal cut diamond proportions instead.
In Tolkowsky’s initial publication, he stated that the ideal cut diamond should only have a table proportion of 53%. However, it has now been scientifically proven that an ideal cut could have proportions outside of this value and diamonds with slightly bigger tables can also achieve ideal optical properties.
Both GIA & AGS had also came up with comprehensive tables of proportions and cutting guidelines. You can download the AGS cutting guidelines here and GIA proportions chart here to do your own comparisons and analysis.
My Personal Criteria is Even Stricter Than Both GIA & AGS Labs
Over the years of examining and analyzing diamonds, I had tabulated my own set of parameters for selecting a ideal cut round diamonds. While it is modeled after Tolkowsky’s initial findings and studies from GIA/AGS, my parameters are much more stringent.
Here’s why…
This tighter set of parameters helps to filter diamonds that are the cream of the crop and I personally use it to handpick diamonds for myself. I strongly recommend that you apply these parameters when searching for your own diamonds. It will not only help you save time but weed out the badly cut diamonds as well.
Here, I want to highlight that proportions should only serve as an initial filtering process. In order to confirm light performance, you will need to rely on idealscope or ASET images for analysis.
Beyond4Cs.com’s Ideal Cut Proportions for Round Diamonds
| Table % | 54.0% to 57.0% |
| Depth % | 61.0% to 62.5% |
| Crown Angle | 34.0° to 35.0° |
| Pavilion Angle | 40.6° to 41.0° |
| Lower Girdles | 75% to 80% |
| Star Facets | 50% to 55% |
| Girdle Thickness | T – M – ST |
Now, with all the technical specifications laid out, you might assume that all the diamonds in the market should be polished to ideal proportions if cutters simply followed a standard formula. However, the truth is far from that.
In fact, it is estimated that 90% of the round diamonds are cut to dismal proportions by choice.
As a consumer, here’s your bottom line when selecting a round diamond for light performance. There’s ABSOLUTELY NO wriggle room when it comes to proportions. Even if a diamond just barely failed to meet these proportions, it is an INSTANT REJECTION and you will have to dump the stone.
When buying diamonds, the ideal proportions matter and precision is required. Even if a diamond has just a 0.2° deviation in pavilion angles (41.2°), it WILL impact light performance. It doesn’t matter whether it has been graded as a triple excellent diamond or a triple ideal stone.
I have to reemphasize here: if the proportions aren’t correct, light performance will be adversely affected. (Granted, there could be outliers but the odds of you finding a well cut diamond outside of these proportions are extremely low.)
Why You Need to Avoid Round Cut Diamonds With Non-Ideal Proportions
Despite my advice, I know there are some readers and internet trolls who will still say stuff like: “Does having something slightly out of the range REALLY affect the light performance or something like that?” or “So what if the pavilion angle is 0.2°? If it were such a big issue, why did GIA still grade the diamond as a triple excellent rating?”.
Well, check out the examples of GIA triple excellent diamonds below. These are diamonds with near misses in proportions and I want you to look at how a small variation can affect the light return of the diamond in a big way.
The ASET imagery reveals significant light leakage and poor edge-to-edge brightness for both diamonds.
Diamond light performance is bounded by the laws of physics and it has a direct correlation to the facet proportions. So, if you are thinking about buying a diamond with proportions that don’t conform to the table I laid above, you better be asking yourself a big fat WHY.
Why should you settle for a diamond with less than ideal proportions when there are literally hundreds of diamonds out there available in the market? In contrast, let me show you what a diamond that is cut for ideal light performance looks like.
This diamond has top notch light performance and extreme cut precision.
In fact, I’ve recently purchased the diamond above and you can read the full review of the engagement ring here. I’ve even recorded a video that compares how well the diamond sparkles in various environments.
Although I’ve been in the trade for many years, I’m also a consumer like many readers as well. And when I shop for a diamond, I’m super anal about cut quality because I want the most sparkly diamond that money can buy.
Related Articles
About The Website:
Leave A Comment
Latest Posts From Our Blog
Join Us On Social Media!
Visit The Gallery For Ideas!
164 Comments
Hi Paul,
Per your super ideal diamond proportions chart, how significant of an impact on the cut would a crown angle of 35.5 and pavilion angle of 41.2? The ring I am looking it has the other dimensions within the ideal ranges you listed above (depth of 62.3% and table of 57%).
A pavilion angle of 41.2° will almost always result in light leakage under the table.
Thanks so much Paul! What impact does the crown angle of 35.5% have even though it is just slightly off the super ideal cut diamond proportions?
The problem with crown angles is that they need to work together with the rest of the diamond proportions (i.e. pavilion, table, depth etc..) to give a fuller picture. You can’t just look at the crown angles alone and try to analyze stuff. Get an idealscope/ASET image of the diamond and it will reveal details of the stone’s brilliance in an objective manner.
And I’ve highlighted and explicitly mentioned that you need tangible data to confirm the brilliance of a diamond after using filtering out choices with the best proportions. That’s because even if a diamond had ideal proportions, there can still be variations in light performance.
Take this example below which has facet proportions that match my table. But light return can still be improved!
hi paul,
thanks for your guide…after reading your strict criteria, i’m looking at a diamond and it is showing these stats..can you let me know if it has an ideal depth and table for round diamonds and the specifications of your ‘cream of the crop’ cut?
table: 57
depth: 62.3
crown angle: 35
pavilion angle: 41
girdle: medium – slightly thick (faceted) 4%
You need scope images like ASET, idealscope and H&A to do that. Numbers don’t reveal much.
https://beyond4cs.com/buying-diamonds-blind/
Paul,
I have my eyes on one of two diamonds 2.0 + Ct round, (I) Color, S2 Clarity. The GIA Report link is:
http://www.bluenile.com/certs/6205654625.pdf?params=cHJvZHVjdD1CTiZwaG9uZT0xKzg4OC01NjUtNzY0MSZsaW5rPWh0dHAlM0ElMkYlMkZ3d3cuYmx1ZW5pbGUuY29tJTJGX0xEMDYzNzE4MDMmc2t1PUxEMDYzNzE4MDMmbGFiPWdpYSZjb3VudHJ5PVVTQSZjdXJyZW5jeT1VU0Qm
And
http://www.bluenile.com/certs/2186529173.pdf?params=cHJvZHVjdD1CTiZwaG9uZT0xKzg4OC01NjUtNzY0MSZsaW5rPWh0dHAlM0ElMkYlMkZ3d3cuYmx1ZW5pbGUuY29tJTJGX0xEMDYyOTYzNTAmc2t1PUxEMDYyOTYzNTAmbGFiPWdpYSZjb3VudHJ5PVVTQSZjdXJyZW5jeT1VU0Qm
They are both identical cut and have ideal depth and table for round diamonds but I have concerns over its CLARITY CHARACTERISTICS and comes with GIA report.
My questions to you are:
(1) Are they any good?
(2) Does the CLARITY CHARACTERISTICS makes a big difference?
(3) In comparison: which one of them is much better than the other?
(4) What are your recommendations? Should I proceed forward with that purchase?
Thank you.
It is a bad idea to buy such a large sized diamond with low clarity ratings blind.
You need to read this: https://beyond4cs.com/buying-diamonds-blind/
Correction :)
Hi Paul,
Hope all is well..
I’m looking for the best round diamond for my engagement ring but one of the jewelers I visited showed me a triple excellent GIA certified diamond that looked stunning to me. This is my first time buying an item that is so expensive and I am getting the jitters.
Is there any red flags on this stone? GIA report number: 2198106970, Price almost $2k.
Appreciate for any tips on what to look for in a diamond in terms of the best gia ideal cut diamond proportions? I value your opinions and comments and I want to learn how to buy the perfect diamond ring without getting duped.
Many Thanks,
Zach
Crown angles are too steep and will result in light leakage. Keep it under 41.0 degrees. Follow this guide carefully; https://beyond4cs.com/step-by-step-guide/
Hi Paul, love your website! I am looking to buy an engagement ring in the near future, doing the initial research currently. Is this a good buy, especially in term of the cut and having the best proportions in a diamond?
https://www.jamesallen.com/loose-diamonds/round-cut/1.11-carat-h-color-vs2-clarity-excellent-cut-sku-714133
Many thanks!
The diamond is good but not great in terms of cut.
I would recommend buying this stone instead: https://www.jamesallen.com/loose-diamonds/round-cut/1.12-carat-g-color-vs2-clarity-excellent-cut-sku-843690
It’s a much better choice in terms of light performance and also offer immense value for money.
Thx for the reply Paul, would you say that the diamond you recommended close to their “true hearts” range?
Yes.
Hi Paul,
Was wondering if you could chime in on the below diamond’s cut quality. I was a bit price strapped, but I felt like this was one of the better diamonds I could find for the money.
https://www.jamesallen.com/loose-diamonds/round-cut/0.74-carat-k-color-vs1-clarity-excellent-cut-sku-827118
The crown angle is a tad too high and this generally translate to some light leakage under the table facet. In this particular diamond, you actually can see the light loss from the video. Overall, it’s still a decent diamond. Not the best but still better cut than the majority of diamonds in the market.
Hi Paul, can I ask what’s your view fancy cut such as 100+ facets round diamond? I recently saw one, the cut is not graded overall as excellent overall as only round brilliant would be graded 3 Ex, but otherwise I see the polish and symmetry both Ex, also compare the cut measure with your suggestion, seems pretty much in line (Table, Depth, Crown, Etc). Color is F, Clarity is VS1 on the certificate (HRD issued) however I can’t see anything with 10X loupe, and it’s definitely a lot more sparkling then same weight F color VVS1 3Ex round brilliant stone. I read that you thinks HRD is pretty much in par with GIA, so I wonder if you have any concerns on the 100+ facets?
Thanks
Yifang
https://beyond4cs.com/shapes/round/solasfera-vs-star-129/
Hi, great article and incredible informative site. i’m looking at a:
0.9 ct
I clarity
VVS1
6.21-6.24×3.77
The seller said it’s looks bigger on top but smaller on bottom? what would you price this diamond? and is a good buy?
Read this: https://beyond4cs.com/diamond-prices/
Hi Paul,
I am looking for a diamond that will fit into a 1 ct halo setting 6-6.5mm.
Can you tell me what I am gaining with the more expensive of these 2. they both look nice.
Really appreciate your guidance.
Thanks
Richard
http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3577089.htm
https://www.jamesallen.com/loose-diamonds/round-cut/0.92-carat-i-color-vs1-clarity-ideal-cut-sku-902220
You are gaining optical precision with the White Flash diamond. Size wise, the 0.98 is also closer to a 1 carat stone.
The James Allen diamond has a slightly larger table than I would normally recommend. It compromises slightly on fire for brightness.
Anyway, I personally won’t buy both diamonds because they aren’t good enough by my standards (I’m really anal this way).
This is what I would recommend instead: http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3597937.htm
Hi Paul,
I have a low budget of $1000 USD for a diamond and setting, but I really want a really good quality diamond. I am looking at a .23 carat, D color, IF clarity diamond for $550. The GIA Report # is 2186473118. Is this a good buy?
Thanks,
-Patrick
Hi Paul,
Your website is very informative! Can you help me decide if I should go with this diamond. I have a budget under 1k for the diamond and setting and would like to have a quality diamond. I am interested in a RB 0.23 carat, D color, IF clarity, Triple excellent, GIA # 2186473118. The diamond angles are within your strict guidelines parameter. The cost is $550. I’m not necessarily looking for a diamond with the best proportions or numbers as long as it sparkles! Is this a good buy?
Thanks,
Pat
Read these:
https://beyond4cs.com/buying-diamonds-blind/
https://beyond4cs.com/diamond-prices/
If you are low on budget, buying a D IF is not the best idea. Stick with something like G VS2 to save money when both diamonds will look identical to each other.
Hi Paul, thank you for sharing your knowledge.
There are two diamonds I am interested in
Table – 56 / Crown – 35.5 / Pavilion – 40.6 / Depth 62.2
Color G – Clarity VVS2 and its only characteristic is “Pinpoint”
https://www.jamesallen.com/loose-diamonds/round-cut/0.91-carat-g-color-vvs2-clarity-excellent-cut-sku-820451
Table – 56% / Crown – 35 / Pavilion – 40.6 / Depth 61.9
Color H – Clarity VVS2 with characteristics Pinpoint/Cloud/Feather
https://www.jamesallen.com/loose-diamonds/round-cut/0.90-carat-h-color-vvs2-clarity-excellent-cut-sku-905839
They both in my budget..which is the better bet?
Thnx
Hi Faab,
I don’t bet when it comes to buying diamonds. I always make rational decisions based on tangible data.
Both stones are pretty well cut but not the best yet. I did a search and would recommend this stone instead:
https://www.jamesallen.com/loose-diamonds/round-cut/0.93-carat-h-color-vs2-clarity-ideal-cut-sku-1004014
Hi Paul
What do you think of the below diamond?
Measurements 6.18-6.22×3.85
0.90 F SI1 Excellent cut, polish and symmetry
table – 56
depth – 62
pavillion 40.6
crown 35.5
lower girdle 80
star facet 50
medium faceted 3.5
cutlet none
buying online is not an option for me, there are no images available at the moment. The seller can guarantee it is eye clean.
Well, I’m sorry to say this but it’s pretty silly to buy a diamond blind when there are other jewelers who can offer better services and products.
Read this: https://beyond4cs.com/buying-diamonds-blind/
HI Paul,
What do you think of this one? Table is bigger than what you recommended and falls outside the “best numbers” in the table above.
http://www.briangavindiamonds.com/diamonds/diamond-details/1.245-i-vs1-round-diamond-ags-104074030059
Thanks.
This stone is very well cut as evident by its ASET and Idealscope image. It’s a great stone and the fluorescence is a plus.
Hi Paul,
Would you be concerned if the table size is 58%, but all other measurements are within your standard? Idealscope image and ASET also looks good. Will a diamond only look good and sparkly if it falls within a certain range of best table % size or depth % ratio?
Thanks
No. It’s not a problem if the ASET checks out.
Hi Paul,
I’m currently looking at a 0.5ct.round with the following numbers and measurements
table – 56
depth – 61.1
pavillion – 40.8
crown – 34
Is it good? Would love to hear your thoughts on this. Thank you
Best Regards
Proportions and dimensions look good on paper. Get scope images to reveal light performance and cut precision quality.
https://beyond4cs.com/grading/aset-reference-charts/
https://beyond4cs.com/hearts-and-arrows/
Hello Paul,
thank you so much for giving advice to people.
My finace and I want to get just a small diamond, our budget is about 460 Dollars. I was trying to follow your instructions when looking for one. Could you tell me your opinion on these? Would you recommend any? Thank you very much!!!
https://www.jamesallen.com/loose-diamonds/round-cut/0.30-carat-k-color-vs1-clarity-excellent-cut-sku-864332
https://www.jamesallen.com/loose-diamonds/round-cut/0.30-carat-k-color-vs2-clarity-excellent-cut-sku-1015219
https://www.jamesallen.com/loose-diamonds/round-cut/0.31-carat-k-color-vs1-clarity-excellent-cut-sku-850115
https://www.jamesallen.com/loose-diamonds/round-cut/0.32-carat-k-color-vvs1-clarity-excellent-cut-sku-879002
This would be the best diamond out of those you shortlisted: https://www.jamesallen.com/loose-diamonds/round-cut/0.32-carat-k-color-vvs1-clarity-excellent-cut-sku-879002
Thank you so much, Paul!
The certificate says it has internal graining. What does that mean? Would that be eye-visible? Also, it says that the color is K – faint brown. I am OK with K color, because I want a golden ring solitaire setting and I´ve heard that the gold makes the diamond look slightly yellowish anyways. But wouldn´t faint brown be too brown? (It doesn’t seem any more brown to me than other diamonds though).
Also after some more time I shortlisted more diamonds at James Allen with their search bar => https://beyond4cs.com/go/ja/
Is the one you suggested first still the best of them?
Thank you very much for your help!!! It is awesome! :)
I did a search for you and would recommend this diamond: https://www.jamesallen.com/loose-diamonds/round-cut/0.30-carat-k-color-vs1-clarity-excellent-cut-sku-921708
Thank you so much for your recommendation, it is very helpful! I appreciate it tons! It looks beautiful! I noticed that it it has medium blue fluorescence, so it will not look brown-ish?
A K is a K. It will look brownish. If you want a diamond that doesn’t show color, you need to go up to a G.
The fluorescence isn’t of consequence. No worries there. This is an ideally cut diamond with outstanding optics.
Paul
Could you help me rank the three below from best to worst and explain why? I’m looking for overall performance while considering the value.
The 2.5 VVS2 seems to have the best overall cut angles and percentages yet it appears the most dull on the video, any thoughts on this as well?
https://www.jamesallen.com/loose-diamonds/round-cut/2.51-carat-j-color-vs1-clarity-excellent-cut-sku-1028758
https://www.jamesallen.com/loose-diamonds/round-cut/2.50-carat-j-color-vvs2-clarity-excellent-cut-sku-1065058
https://www.jamesallen.com/loose-diamonds/round-cut/2.50-carat-j-color-vvs1-clarity-excellent-cut-sku-827114
This would be the only stone that’s passable: https://www.jamesallen.com/loose-diamonds/round-cut/2.50-carat-j-color-vvs2-clarity-excellent-cut-sku-1065058
I would dump the rest because of their bad proportions and ratios.
Paul,
Thank you kindly for your reply. Your time is invaluable to me!
https://www.jamesallen.com/loose-diamonds/round-cut/2.50-carat-j-color-vvs2-clarity-excellent-cut-sku-1065058
Can you explain what you mean? “passable” is not exactly what I was hoping for. I understand that this was the best of the three in your opinion, yet I don’t think you are exactly pleased with the choice or probably wouldn’t go with it. If so, could you suggest one or two alternatives that would be better in that 2.5ct area?
I really appreciate your time and hope you can help me.
I set very high standards when buying diamonds personally or when I make recommendations. I would eliminate the others based on their high crown angles.
Get an idealscope image for this stone: https://www.jamesallen.com/loose-diamonds/round-cut/2.50-carat-j-color-vvs2-clarity-excellent-cut-sku-1065058
It should turn out well.
If I were to pick, these would be what I would recommend:
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3608314.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3508579.htm
Hello Paul,
What are your thoughts on the following.
https://beyond4cs.com/go/ja/ SKU:1133614
I am looking for a round diamond 1-1.1ct with ideal depth and table for a round diamond. Do you have any recommendations if this particular one does not look good to you?
Thanks
It’s a mediocre stone.
These are much better options to select from:
https://www.jamesallen.com/loose-diamonds/round-cut/1.09-carat-g-color-vs1-clarity-ideal-cut-sku-1123680
https://www.jamesallen.com/loose-diamonds/round-cut/1.04-carat-h-color-vs2-clarity-ideal-cut-sku-1003594
https://www.jamesallen.com/loose-diamonds/round-cut/1.13-carat-h-color-vs2-clarity-ideal-cut-sku-1003596
Paul,
Thanks for the reply, I appreciate your help. Thoughts on this one?
https://www.jamesallen.com/loose-diamonds/round-cut/1.03-carat-h-color-si1-clarity-sku-702887
The diamonds you recommend are beautiful but unfortunately out of my price range. I am trying to keep it around 6K.
It’s a good stone.
Just wanted to say thank you for all your help. I’ve learned so much from your site and helped me on my purchase. At first I was set on getting one from a site that i thought was reputable due to their popularity. Fortunately, I decided to do more research and found your page, which taught me otherwise. I applied your personal guidelines concerning angles of the crown, pavilion, along with the 4cs and table/depth measurements to the stone I picked. Your knowledge gave me the confidence knowing I chose the right one. Thank you again.
When you give your curated list of ideal diamond cut proportions for table size and depth, you do not mention Girdle Thickness or Culet Size. What ranges/values do you suggest for these characteristics?
No culet. There’s a range of girdle thickness I would accept: thin – medium – slightly thick (*I would avoid round cut diamonds that have a consistent “slightly thick” girdle across the board.)
Paul,
I am looking at some round cut options on james allen. Unfortunately, some of their stones do not have an available Idealscope or ASET image. I still feel as though this stone falls perfectly within your parameters and has an extremely beautiful cut. Do you agree? The bubble in the girdle does not appear to affect it too much.
https://www.jamesallen.com/loose-diamonds/round-cut/1.51-carat-e-color-vs2-clarity-excellent-cut-sku-1862334
My price range is 12-13k for the stone and I want to get her something she will love. Thanks for all of the help you provide to folks like me!
Nope. The cut standards on this round diamond is bad.
I did a search for you and would pick these 2 instead:
https://www.jamesallen.com/loose-diamonds/round-cut/1.50-carat-f-color-vs2-clarity-excellent-cut-sku-1885113
https://www.jamesallen.com/loose-diamonds/round-cut/1.56-carat-f-color-vs2-clarity-ideal-cut-sku-1003592
Hi Paul,
Thank you for your informational website and willingness to be a great resource for such a daunting purchase! I have learned a lot about diamonds and I know I am making a much more informed purchase thanks to you. It is very comforting knowing I will be buying something much more beautiful/worthy than if I just bought a diamond blind from an online retailer like I had originally planned to do.
The diamond I am looking at meets most of your GIA ideal cut diamond proportions for “buying super ideal rounds”, but I wanted your opinion on whether I should keep looking or settle on this diamond.
The seller is asking for $8175 for a 1.33 round GIA VS2 I color triple ex stone no fluorescence.
Here are the proportion numbers from the GIA report:
Depth: 62.8%
Table: 56%
Crown Angle: 36.5
Crown Height: 16%
Pavilion Angle: 40.8
Pavilion Depth: 43%
Star Length: 55%
Lower Half: 80%
Girdle: thin to slightly thick, faceted, 3.5%
Cutlet: None
Finish
Polish: Excellent
Symmetry: Excellent
I am looking for a diamond that is:
solitaire
Carat: 1.1 – 1.3
Cut: round; ideal or better
Color: F or better
Clarity: SI2 or better
I noticed that the stone is slightly steep compared to the numbers you recommended for ideal depth and table for round diamonds. My apologies if this is too much information. I appreciate your assistance and hope to hear from you soon! Thank you!
There’s a vast difference in the cut proportions of the diamond above against what I recommend.
1) Crown angles are too high. The balance of fire/brilliance has been compromised by light physics.
2) Diamond is deep. It will face up smaller for its weight.
Both are signs that immediately fail my first round of filtering without even looking at any further scope data.
Hi Paul,
Thank you for your prompt reply! I greatly appreciate it. Please excuse my naivety for I thought being out very slightly for the crown angle and depth would be acceptable. That was foolish of me!
I am looking at another diamond that DOES meet your crown angle standards and is very close to your depth standards. I am hoping the +.1 is not a deal breaker! The details are below.
A concern for me is the girdle, as you mentioned in one of your comments that you would avoid diamonds that have a consistent “slightly thick” girdle across the board.
Can you please let me know your thoughts on this diamond?
Depth: 62.6%
Table: 57%
Crown Angle: 35
Crown Height: 15%
Pavilion Angle: 41
Pavilion Depth: 43.5%
Star Length: 50%
Lower Half: 80%
Girdle: slightly thick, faceted, 4.0%
Cutlet: None
Finish
Polish: Excellent
Symmetry: Excellent
Fluorescence: Faint
Thank you!
You want to read this: https://beyond4cs.com/buying-diamonds-blind/
Hi Paul,
This website has been my #1 resources in my diamond search, so thank you so much for the education.
I’m looking at the below diamond that fits all of your guidelines above. Would this be a recommended stone? I have seen it in person and it looks quite brilliant, just wanted to get your input on the proportions per the GIA report.
Depth: 62.5%
Table: 55%
Crown Angle: 35.0
Crown Height: 15.5%
Pavilion Angle: 41.0
Girdle: thin to medium faceted
Cutlet: None
Thanks,
Ari
The numbers look fine. The caveat here is that having best proportions can only increase the “probability” of finding a great diamond. You will need to have additional scope images or data to confirm performance.
Hi Paul,
My partner and I are looking for a brilliant round cut diamond for her engagement ring. I have read and understood properly that not only do the super ideal cut diamond proportions need to be right but so does the actual image of the diamond and its clarity characteristic plot.
She would like a 1 carat diamond, which seems to inflate the price slightly compared with something lower, but I am happy to pay a more to get a 1 carat which will also be excellent quality.
I would be very grateful if you could possibly send across some diamonds that you would suggest. The PDF version of the reports includes the clarity characteristics image too. I’ve found from what I can afford, I can get good/very good cut with very few clarity marks on the diamond or I can get an excellent cut with quite a few marks.
Thank you in advance and any advice would be appreciated.
Josh
Hi Paul,
I’m looking at a diamond that i really like with the below dimensions. It’s a true hearts and everything is fantastic about it. Only thing that stands out is that it has 58% table. It’s a bit outside your range, but very close. anything to be concerned about?
SHAPE: Round
CARAT WEIGHT: 1.21
COLOR: G
CLARITY: VS1
CUT: True Hearts Excellent
POLISH: Excellent
SYMMETRY: Excellent
FLUORESCENCE: None
L/W/D (MM): 6.83*6.80*4.20
L/W RATIO: 1.00
DEPTH %: 61.60
GIRDLE: Medium – Slightly Thick
TABLE %: 58.00
CULET: None
CERTIFICATE: GIA
CROWN ∠: 35.00
CROWN %: 15.00
PAVILION ∠: 40.80
Do you have a url to view the diamond listing and video?
https://www.jamesallen.com/loose-diamonds/round-cut/1.21-carat-g-color-vs1-clarity-excellent-cut-sku-1910546
It’s a well cut diamond for light performance.
Thanks Paul. Anything else you’d call out or looks like a good diamond?
Really appreciate your help! Your website has helped me tremendously.
It’s a great diamond. Go for it!
Hi Paul,
I’m looking to purchase a diamond with the below specs:
Round
1.3+ carat
VVS1+
E+
Budget of up to US$20k
Would be grateful if you could share your thoughts on this one?
https://www.jamesallen.com/loose-diamonds/round-cut/1.33-carat-d-color-vvs1-clarity-excellent-cut-sku-1942748
Also, are you able to recommend some others for comparison?
The diamond isn’t well cut enough nor does it offer good value. If clarity matters, you should be considering an IF diamond instead of a VVS1 diamond. Truth is, a VVS1 and a VS1 is going to looking identical (assuming every other aspect is exactly the same) to the naked eye. It’s just a waste of money to get a VVS1.
These are 2 better alternatives that I would recommend:
https://www.jamesallen.com/loose-diamonds/round-cut/1.30-carat-e-color-vs1-clarity-ideal-cut-sku-940757
https://www.jamesallen.com/loose-diamonds/round-cut/1.31-carat-d-color-vs1-clarity-ideal-cut-sku-1003601
Hi Paul. I’ve only started researching diamonds for a week or so, and I’ve learned that my standards are too high… With that said, can you please tell me if these two diamonds are good buys, and which you would choose out of the two and why? I know the crown/table is a little out of range, and I’d like to know if it will have any significant effect for this size diamond. Thanks.
http://www.bluenile.com/build-your-own-ring/diamond-details/LD07207197
https://www.jamesallen.com/loose-diamonds/round-cut/2.53-carat-e-color-if-clarity-excellent-cut-sku-2050557
Also, I want to know what is the best height for diamonds? Or is this something that doesn’t matter because it isn’t stated above?
The crown angles affect the dispersion of fire and brilliance. Both are mediocre diamonds I would never consider touching. The height of a diamond is correlated to the crown angles. So, you can use the value of the crown angle and do not have to use the crown height if you want to simplify things.
Hi Paul,
First off, thank you for what you do. You have saved us from a really bad investment with Zales’ Celebration diamonds, which we just returned yesterday.
We are now looking at James Allen and decided on this platinum setting: https://www.jamesallen.com/engagement-rings/halo/platinum-falling-edge-pave-diamond-engagement-ring-item-49997
Following your guidelines as close as possible, I am down to these 4 center stones:
https://www.jamesallen.com/loose-diamonds/round-cut/0.50-carat-f-color-vs2-clarity-excellent-cut-sku-2119215
https://www.jamesallen.com/loose-diamonds/round-cut/0.54-carat-g-color-vs2-clarity-excellent-cut-sku-2097854
https://www.jamesallen.com/loose-diamonds/round-cut/0.50-carat-e-color-vs2-clarity-excellent-cut-sku-1141185
https://www.jamesallen.com/loose-diamonds/round-cut/0.51-carat-d-color-vs2-clarity-excellent-cut-sku-1863766
I asked for idealscope images per your advice but they are unable to provide them for these stones as they are not local to them. Based on their specs, which one do you think gives us the best value? I am also open if you have any other suggestions. Our budget for the center stone is up to $1700.
Hi Paul,
Thanks a lot for writing your step-by-step wiki. Helped a lot.
Any recommendations about the following diamonds –
1) https://www.jamesallen.com/loose-diamonds/round-cut/1.13-carat-i-color-vs2-clarity-excellent-cut-sku-2061748
2) https://www.jamesallen.com/loose-diamonds/round-cut/1.20-carat-i-color-vs2-clarity-excellent-cut-sku-1769239
[1] and [2] have a score of 1.3 and 1.4 respectively from the HCA diamond proportions calculator. Both have a small cloud under the table which does not seem to be visible under 10x magnification on JamesAllen’s website. Do you agree with my observation?
Thanks!
Both diamonds are eyeclean and inclusions are not an issue. This would be the slightly better cut diamond:
https://www.jamesallen.com/loose-diamonds/round-cut/1.13-carat-i-color-vs2-clarity-excellent-cut-sku-2061748
If you are looking for better value, this diamond would offer better carat size for money:
https://www.jamesallen.com/loose-diamonds/round-cut/1.20-carat-i-color-vs2-clarity-excellent-cut-sku-1769239
It’s a well cut diamond. Good find!
Hi Paul,
I’m looking to buy a diamond around .45 ct with budget $1000 to $1300. If possible can you please find the best one for me with cause I’m pretty new to this things and this my first time buying diamond though.
https://www.jamesallen.com/loose-diamonds/round-cut/0.46-carat-i-color-vs1-clarity-excellent-cut-sku-2093749
This one seem really nice cut. Is it right Paul?
Thanks Paul
Terrible diamond in terms of cut quality.
These 2 diamonds are much much better choices:
https://www.jamesallen.com/loose-diamonds/round-cut/0.43-carat-i-color-vs1-clarity-excellent-cut-sku-2145788
https://www.jamesallen.com/loose-diamonds/round-cut/0.41-carat-e-color-si1-clarity-excellent-cut-sku-2139337
Thanks for your help Paul.
Can you please help me to find a little bit bigger one around .45 to .50 ct.
Thanks in advance.
Can you take a look on this for me please Paul.
https://www.jamesallen.com/loose-diamonds/round-cut/0.46-carat-g-color-si1-clarity-excellent-cut-sku-1970303
Thanks for your help
This diamond is well cut as well. Good choice!
Hi Paul, would like to ask for your opinion about the ideal depth and table for round diamonds and whether they matter. Which would you choose between these 2? On one hand, the 0.6ct is an I colour while the other is F, but the 0.6ct looks abit cloudy based on the pictures. However i only have a 45% side picture of the 0.44ct diamond which i can send to you to have a look.
https://www.jamesallen.com/loose-diamonds/round-cut/0.60-carat-i-color-si2-clarity-excellent-cut-sku-2153332
http://www.bluenile.com/sg/diamond-details/LD07690594
Thanks!
This is a fine diamond: https://www.jamesallen.com/loose-diamonds/round-cut/0.60-carat-i-color-si2-clarity-excellent-cut-sku-2153332
As for the BlueNile diamond, I cannot offer constructive advice without data.
Hey thanks Paul for the opinion but i still decided to go for the Blue Nile’s one as i tried asking my FW some questions, and even though she did not know i was asking about a diamond but in her opinion quality is better than quantity, so i think the F VVS1 fits the bill better. I also contacted BN and they told me that they could take a quick look at the arrows of the diamond i am buying. Cross my fingers and hope all will be well =D
BTW for the bro up there, if you are okay with an I coloured diamond, the jamesallen diamond that i posted might be a good choice for you too considering your budget =D
Hello Paul,
Before committing, please find below a diamond I am interested in, the diamond proportions calculator score is 1.5 while using the crown and pavilion % and 2.6 while using the crown and pavilion angle
https://www.bluenile.com/build-your-own-ring/diamond-details/LD07796218
What would you be your advice please?
Thank you for your time
Best,
It’s not a well cut stone. https://www.bluenile.com/diamond-details/LD07788469
This would be a much better option.
Paul I need your help applying all this information to the three stones I have narrowed down. I am torn between having a larger stone (1.74) that I think performs well if I am interpreting your information correctly with the exception of just one section of the stone. And then one that is smaller 1.51 that is considered A Cut Above on White Flashes website.
Can you please let me know where I can send you my images (below are the AGS ideal diamond cut proportions) so you can tell me what you think of the larger stone. I had to pay for it for them to bring it in and do the analysis so the reports are not on the site for the diamond but the video is.
https://beyond4cs.com/go/wf/
SHAPE: Round
CARAT WEIGHT: 1.74
COLOR: I
CLARITY: S1
CUT: Ags Ideal 0
POLISH: Ags Ideal 0
SYMMETRY: Ags Ideal 0
FLUORESCENCE: Negligible
L/W/D (MM): 7.67*7.70*4.76
DEPTH %: 61.90
GIRDLE: thin – Slightly Thick
TABLE %: 58.00
CULET: Pointed
CERTIFICATE: AGS
CROWN ∠: 34.1
CROWN %: 14.3%
PAVILION ∠: 41
PAVILION%: 43.5%
The diamond looks well cut. I would have preferred it if the table size was kept a tad smaller.
Hi Paul,
Great website for helping navigating such a detailed purchase. I have been looking at the attached diamond and would appreciate any thoughts you had.
https://www.jamesallen.com/loose-diamonds/round-cut/0.91-carat-g-color-vs2-clarity-excellent-cut-sku-2376023
Thank you
It is a decent stone but not good enough. I would recommend these stones instead:
https://www.jamesallen.com/loose-diamonds/round-cut/0.91-carat-d-color-si1-clarity-excellent-cut-sku-2281903
https://www.jamesallen.com/loose-diamonds/round-cut/0.90-carat-f-color-si1-clarity-excellent-cut-sku-2264726
Paul, you’re a godsend. Thank you so much for the work you do, and for going above and beyond to help people out. If it weren’t for you, I’d likely have gotten a smaller and less beautiful stone at one of the big brand retailers out of a lack of information.
I was wondering if you could give me your read/preference on these choices.
1. https://www.jamesallen.com/loose-diamonds/round-cut/1.20-carat-g-color-vvs2-clarity-ideal-cut-sku-2336286
2. https://www.jamesallen.com/loose-diamonds/round-cut/1.22-carat-g-color-vvs2-clarity-excellent-cut-sku-2281080
3. https://www.jamesallen.com/loose-diamonds/round-cut/1.20-carat-g-color-vvs1-clarity-excellent-cut-sku-2186949
Thank you so much for all the help!
You did very well in shortlisting these round cut diamonds. They are all great choices and I personally love the first stone the most because of its cut precision and light performance.
Hi Paul,
Great website! I would appreciate your opinion on this diamond. I did a lot of research, mostly on your website and found this to be the most ideal diamond in my price range out of what is available right now. Please let me know your thoughts.
https://www.jamesallen.com/loose-diamonds/round-cut/1.20-carat-j-color-vvs2-clarity-excellent-cut-sku-2279949
Thanks!
It’s a decent stone but the table size is a little too large for my liking. Personally, I would choose this particular option over the one you picked.
https://www.jamesallen.com/loose-diamonds/round-cut/1.20-carat-j-color-vs1-clarity-ideal-cut-sku-2219385
Hi Paul,
I cannot tell you how much I have learned from your excellent website and I’m happy to say I have actually made use of the knowledge I picked up in choosing my first diamond.
I bought a GIA triple Ex stone and I feel its real-life light performance matches with its good HCA score (0.8). It was the first diamond I bought. Regardless of its colour and clarity, could you tell me whether this stone with the following proportions is of a good light performance in your opinion?
Table 58%
Depth 60.2%
Crown angle 33 degrees
Pavilion angle 40.8 degrees
Thin to slightly thick girdle (faceted) 3.5%
Cullet: none
P.S. It is a VS2 K stone with a faint fluorescence which in my eye made it look at least like a J if not I.
Thanks,
Ernest
Hi Paul –
Thanks very much for your excellent information and advise.. I’ve been looking for diamonds within your ideal cut specifications but am having trouble finding ‘the one’.
I’d like to be around E color and IF clarity (could go to VS1), 1.7-2.0 carat, with absolute top cut with ~ $25-30k budget.
I’m currently considering one with the following specs (GIA cert):
7.89 – 7.95 x 4.71
1.78 carat
E / IF
Excellent cut, polish, symmetry
No florescence or cutlet
Medium faceted girdle
Table 58%
Depth 59.4%
Crown Angle: 34.0
Pavilion Angle: 40.8
Star: 55%, Lower: 80%
HCA score 0.9, Excellent in all 4 categories
I have Aset & Idealscope images which look great, but am not able to get hearts & arrows images. The stone is on b2c.. I have not found anything fitting my specifications on James Allen, Whiteflash, or Brian Gavin.
Really appreciate your time and feedback!
-Matt
If cut quality matters, the table and depth proportions for this diamond will instantly make me reject this option out of the door.
gia 6221767475 my wife selected this ring at a local jeweler, i was present it is being placed into a gold band to match her original set.
Purchase price was 9.8k As mentioned we compared this to various weights, diamonds with similar gia ideal cut diamond proportions, color qualities etc I did look at it through a 10x loupe along with the others and this one actually made us both happy. I have a feeling you’d state you would not have purchased it. Question is, was the price reasonable? thank you
Yep, you are right. The crown angles are way too low.
Hi Paul, would you mind giving your opinion on this diamond please? Many thanks.
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3800303.htm
It’s an extremely well cut diamond for light performance and is eyeclean. Great find!
Thanks for your reply Paul, much appreciated. If you don’t mind, I have one more question. What do you think of these two diamonds as cheaper options? Clearly they’re smaller but how do they stack up otherwise, considering they’re considerably cheaper? They seem well-cut and both are eye clean. To me, the ideal-scope and ASETs check out (looks better to me on the second diamond). I used the HCA diamond proportions calculator and they rated, 1.5 and 1.1 respectively. Thanks again for your help.
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3793653.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3660690.htm
I don’t care about what the HCA tells me. In this case, you aren’t buying blind and the tool is useless.
Both these diamonds are fantastic options that are cut for light performance and sparkle.
This would be the stone I will personally buy for practical reasons: https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3793653.htm
HI Paul –
I really need your help.. I’ve studied everything on your site and believe I have found my short list of excellent cut stones which fall within your ideal specifications and best proportions.
But, with all of the stones falling into the premium collections of the respective sites (i.e. Brain Gavin Black, James Allen Truehearts, Whiteflash A Cut Above) it get’s very difficult to know how to choose between them. I’ve tried hard to look at the hearts and arrows images and find any faults, but I just don’t feel like I have enough experience to make the final call.
I know my list is still a bit long – this is the top 10 I could find in terms of absolute best cut at around 1.5 carat.. D or E color, VS1 clarity or above.
I’d like to complete my purchase very soon and I would feel much better having your opinion before I make this big decision.
Can you help me narrow it down, or at least give me some hints how to select among what all seem to be top stones?
I do really value your time and feedback.
Thanks!
-Matt
I would love to help. Please get in touch with me via email directly.
Hi Paul
Love the advise and all the help. I have roughly a $7-9k budget and have been looking for a while.
Currently I am flirting with considering one with the following specs:
6.51 – 6.55 x 3.88mm
1.00 carat
E
VS2
Excellent cut,
Excellent polish
Excellent symmetry
No florescence
No cutlet
Medium faceted girdle 3.0%
Table 59%
Depth 59.4%
Crown Angle: 32.0
Pavilion Angle: 41.0
Star: 50%
Lower: 75%
GIA Report #: 1186067030
I know that the best depth for diamonds is above 60% but does how much does it matter?
The stone sits at the bottom of my price range at $7k. I am interested in your thoughts on the stone and wondering if you think that I should wait for something better or jump on this now? Thanks and all the best.
-Jack
Diamond isn’t well cut. One thing that puzzles me is that there are so many diamonds and vendors out there. Why are you even limiting yourself to this stone?
Hi Paul,
Looking for some advise on the following stone. The jeweler told me that this cushion had super ideal cut diamond proportions:
6.84 x 6.82 x 4.86 mm
Cushion Modified Brilliant
2.01 ct
G color
VS 1 clarity
Polish excellent
Symmetry very good
No florescence
Depth: 71.2%
Table: 57%
Girdle: Thick to Very Thick, faceted
Culet: None
I’m surprised that I’ve seen this stone in my price range, since other similar (or worse) looking ones seem to be thousands more. Do you see any red flags here? Do the depth or girdle raise any concerns here?
Thanks,
Danny
I can’t offer any useful advice without tangible data. With cushion cut diamonds, numbers don’t matter because they don’t reveal the full story. You will need a video or an ASET to do so.
Hi Paul,
Most of the data and chat are around round diamonds. Can you please shed some light on princess cut diamonds please? what would be a good table size if I am looking for a 1-1.25 carat, D/E/F, up to VVS2? Your help will be greatly appreciated.
Thanks
We have a section on the website specially dedicated to princess cut diamonds. You might want to check it out for a comprehensive guide.
Hi Paul,
Thank you so much for the in-depth information on your site. It’s very helpful.
I’m am looking for a diamond for a setting that will leave the sides and bottom of the center diamond exposed. Accordingly, I’m wondering if leakage wouldn’t be as bad in this case (or even beneficial) since very little of the stone is blocked by the setting. Do you have any opinion on this?
More specifically, I am considering this stone http://www.levycreations.com/diaCertificates/5236184760.jpg, which scores close to “excellent” on the Holloway score at 2.3. However, since the score improves by .9 points if the pavilion angle changes by just .1, I’m skeptical as too how reliable the Holloway score is. (By the way, I’m looking at this diamond vendor, and not a larger one, due to its good reputation among people I know)
I would love to hear your thoughts.
Thank you!
Well, I have already laid out the answers for you in this article. Just do your own comparisons against the ideal diamond cut proportions I recommended. Not that hard right? Why settle for this mediocre diamond when there are literally thousands of other better stones out there? Dump it.
Hi Paul,
Just want to say thanks in advance for all the great information you have provided, it has really helped me while shopping for a diamond.
I’m currently looking at this diamond: https://www.gia.edu/report-check?reportno=6177010146.
Could you kindly let me know your opinions on this diamond and if $6800 CAD would be a good price to pay for this diamond from a independent jewelry store?
Do you also have a personal email address you can email you at would like to reach out to you for further information on diamond buying as well.
Thank You!
Hi Paul, thanks so much for your invaluable insights.
Do your super ideal cut diamond proportions and specifications for a round brilliant cut also apply to fancy colored diamonds? (I’m looking for a reasonably priced, quality loose pink diamond, and the search has been pretty difficult.)
Many thanks,
Parker
This diamond proportions chart and numbers are only applicable to (white) diamonds in the D-Z range. Fancy colored diamonds like pinks are a totally different ball game and not subjected to similar standards for assessing cut.
Paul!
Been reading your educational blogs and they have been outstanding! you stated whiteflash and Brian Gavin are the two companies where I will see best quality in cut and fire etc
I now have a list to choose from:
Brian Gavin black
https://www.briangavindiamonds.com/diamonds/diamond-details/2.097-g-vs2-round-diamond-bkags-104096148009
https://black.briangavindiamonds.com/diamond-details/bkags-104095888008
White Flash
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3897559.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3753619.htm
There is also a diamond from JannPaul Super Ideal collection. A little pricier than above.
1.91 E VS1 – i have the ASET/ideal, cert that im very happy with. Just the price that is holding me back.
what’s your opinions on the above?
Thanks
Smithy
These are all extremely well cut diamonds for light performance and are eyeclean. Personally, I take on a practical approach when buying diamonds and these would be my top picks to get best value for money:
https://www.briangavindiamonds.com/diamonds/diamond-details/2.097-g-vs2-round-diamond-bkags-104096148009
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3897559.htm
I do have preference for the Brian Gavin option. At the end of the day, you should take into consideration the choice of settings offered by the different vendors. That should be the guiding light on whom to work with as these diamonds are all fantastic options.
Jann Paul is a decent vendor but on the expensive side as they run a retail front.
Hi Paul,
I found this diamond that checks off all the requirements i have, but it is priced lower than similar Diamonds. Only reason i can think of is that the table is 59%, but HCA score is 1.0. What do you think about this particular diamond?
https://www.adiamor.com/Diamonds/Details/D40625994
It’s priced lower because it is NOT well cut and has medium blue fluorescence. If you had read this article, this large table percentage shouldn’t even be a question for rejecting the stone.
Hi Paul, what are your thoughts on a diamond that meets all your requirements but is a 35.1 crown angle? It’s so close! :)
https://www.brilliantearth.com/lab-diamonds-search/view_detail/4898535/
I’m also looking at a similar diamond with nearly identical proportions but the same price (and .05 carats higher). Why would it be the same price? I’m assuming that means there’s an inclusion? (And yes, I am going to ask for photos of both. :) ).
https://www.brilliantearth.com/lab-diamonds-search/view_detail/4898164/
Both looks good on paper. You should contact me via email directly when you have more tangible data on the stones.
Hi Paul!
Long time visitor, first time poster. Love your site and the advice you offer uneducated Joes like me when making such a big purchase!
I see Tolkowsky’s diagram recommends having a depth split of 16.2% and 43.1% and yours has no split but a depth of 61%-62.5% in total. Does this split make any difference?
I’m thinking of buying this diamond: https://www.jamesallen.com/loose-diamonds/round-cut/1.03-carat-g-color-vs1-clarity-excellent-cut-sku-2600687
What’s your opinion?
Thanks Paul,much obliged!
Owen
The split is sort of redundant as it shows the crown height % and pavilion depth percentage. These numbers would correspond to the data for crown angle and pavilion angles respectively. Also, the diamond you picked is exceptionally well cut for performance and is a fantastic choice.
Hi Paul! I’ve read through many of your posts and thank you for all the education you are helping provide. I have a diamond ring I just purchased (but can still return). From what I can tell, the specs seem to match up with your Ideal Cut Proportions, other than the crown angle is 35.5. Can you let me know if you would consider this a well cut stone or would you have another recommendation(s)? I paid $ 7,000 (plus tax). It’s a platinum ring with a halo band containing an additional 48 round brilliant diamonds – 4.0 DWT. Here’s what the GIA grading report reflects:
Shape: Round Brilliant
Measurements: 6.56 – 6.59 x 4.09 mm
CW: 1.08
Color: i
Clarity: VS2
Cut: Excellent
Polish: Very Good
Symmetry: Excellent
Fluorescence: Faint
Table: 56%
Depth: 62.2%
Crown Angle: 35.5
Pavilion Angle: 41.0
ST: 50%
Lower Girdles: 80%
Girdle Thickness: Medium – Slightly Thick (faceted) 3.5%
Cutlet: None
If you feel the proportions are not ideal, I’m totally open to any recommendations you may have, as I’ve seen above sometimes you’ll post links to other diamonds you feel are a better value/better cut. Thanks so much!
The crown angles and the Very Good polish ratings are already yellow flags to me and this diamond won’t even make it pass my initial checks as I had mentioned above. Also, it seems that you already bought the diamond before doing your due diligence. What’s the point of doing crying over spilled milk and finding a well cut diamond now?
Paul, you’re really doing great work on this site! I’m shopping for an engagement ring, have done a lot of research at the sites you recommend, but there is a local jeweler, actually they have 14 stores around the western states, that have really great policies, and I’d really like to buy from them. I’m looking at this
GIA – 1.29 CT – E – VVS2 – 3E – good proportions (all within your guidelines). They do lack any scope images. When I look at it with a loupe, I don’t see the heavy dark/black swords I see in the pictures on different websites. If I move the stone around, I can make out the swords, grey in color, and best I can tell they are complete, intact, and well-proportioned. But I can’t be 100% sure because I have to move it just right to see them, and there is just not enough contrast in color (darkness of the swords). It’s a good price – $13,800 – for a diamond in every other respect is awesome. I really want to work with this store because of their policies (example, they will actually replace the diamond if it ever falls out of the setting and you lose it, they will replate the rhodium on their white gold if/when it fades, 100% trade-up value forever, 60-day buyback etc). Appreciate your thoughts.
There’s nothing concrete I can tell you. I shop with tangible data and if the store was really “great” and really know what they are doing, they would have no problems providing you the ASET/H&A images for proper analysis.
Do your ideal proportions apply to diamonds of all sizes (including diamonds over 2 carats)?
For example, most of the 2+ carat round diamonds that I have seen on your recommended sites (WhiteFlash, James Allen, Brian Gavin) satisfy the ideal depth % and pavilion angle, but rarely satisfy the table % or the crown angle.
They apply to the 2 carat size diamonds too. It’s universal for round diamonds both small or large size. You just need to do your search better and filter down more for the better stones.
Hi Paul,
Thanks a lot for your Ideal Cut Proportions table. I’m trying to find my diamond based on it. However, when I look at a GIA report, I can’t find “Star Facets (%)” and and “Lower Girdles (%)”. I wonder if they are referring to “Start length” and “Lower half length” in GIA report? Thanks so much!
Yep. You are right.
Star Facets Percentage = Star Lenght
Lower Girdle Percentage – Lower Half Length
Hello! First I’d like to say thank you so much for your site and the immense amount of effort that must have gone into compiling all of the information.
After searching around, most of the other sources of information seem a bit biased and also not as complete or thorough as your content here is.
Also, it’s really amazing how much energy you put into answering people’s questions in the comments (even reviewing their would-be purchases).
Just scrolling through all the years of comments on your different information pages, I see all the questions you’ve answered, EVEN when they’re the same questions that have been answered, repeatedly, many times already!
Secondly, I’ve got a question regarding a loose diamond I’m looking to purchase from James Allen for an engagement ring. What’s the best height for diamonds and what’s the best depth for diamonds? Does it matter when it comes to different carat sizes?
I see you’ve mentioned rejecting diamonds not in your ideal proportions (and I have been!), but I’m wondering how strictly this applies to the star length and lower girdle? In my case, they are 47% and 76%, respectively.
Reference: https://www.jamesallen.com/loose-diamonds/round-cut/0.82-carat-i-color-si1-clarity-true-hearts-cut-sku-5561318
AGS Report: https://agslab.com/ym-vdgr/diamonds/104100712001/grading-report
I’ve included the following specs for my diamond in case it helps in reviewing:
—
Certified: AGS 104100712001
Cut: Ideal
Color: I
Clarity: SI1
Weight: 0.828
Fluorescence: Medium Blue
Comments: “Additional clouds not shown”
Light Performance: 0
Polish: Ideal
Symmetry: Ideal
Table: 56.2%
Crown Angle: 34.1
Crown Height: 14.8%
Girdle: Faceted, 1.3% to 4.0%
Girdle Description: Thin to Slightly Thick, Faceted
Pavilion Angle: 40.6
Pavilion Depth: 42.7%
Star Length: 47%
Lower Girdle Length: 76%
Total Depth: 61.0%
Characteristic map includes: Crystal,Feather,Cloud
Culet: Pointed
—
I’m having a hard time finding much with the your ideal proportions in the 0.7 – 0.89 carat range (even 0.9 – 0.99 is pretty slim). There, are, of course many, many, options in the 1+ carat range, but this is out of my budget if I want to retain quality in cut (and thus light performance).
Thanks again, it’s refreshing to find someone online contributing so genuinely the way you do! So, thank you so very much!
I’ve reviewed the diamond here: https://www.jamesallen.com/loose-diamonds/round-cut/0.82-carat-i-color-si1-clarity-true-hearts-cut-sku-5561318
The star facet and lower girdle lengths are perfectly fine. I generally keep stars between 45-50% and 75-80%. It’s actually how the individual facets interact and comes together that really matter. And this is where the ASET image in the grading report and the idealscope image in the listing come in handy.
Now, this diamond is perfectly well cut. You clearly nailed your selection in terms of cut quality. BUT, the diamond isn’t eyeclean. The nasty black looking inclusion will be seen by the naked eyes.
I would ditch that stone. Instead, I did a search for you and would recommend these diamonds instead:
https://www.jamesallen.com/loose-diamonds/round-cut/0.73-carat-i-color-vs1-clarity-true-hearts-cut-sku-5331143
https://www.jamesallen.com/loose-diamonds/round-cut/0.71-carat-i-color-vs1-clarity-true-hearts-cut-sku-5451707
Both are eyeclean and MUCH better options than the diamond because of their eyecleanliness and cut quality.
Hi Paul,
I really appreciate all the knowledge you’ve shared on this site, its been so useful!
I have a couple of questions, how much importance would you put on the measurements? Is there a maximum L/W ratio you would go to on a 0.7 to 0.9 carat stone?
Thanks
If you are referring to a round diamond, L/W ratios need to be kept around 1:1. For other fancy shapes, it really depends on personal preferences. I’ve listed mine in the various tables at the respective pages for the shapes in the navigation menu.
Paul, I’ve really benefited from the information you provide and appreciate it greatly! You say that there should be no ‘wiggle’ allowed and the ideal proportions you mention say that the star should be 50-55, but you also say that you generally accept stars of 45-50. Should I interpret stars as being an exception if everything else works out?
What do you think of these two diamonds? I have a budget of around 50k (can stretch it a bit if needed), and I’m looking for a 3 carat F/VS1 or better with super ideal/nearly super ideal proportions with no more than medium blue fluorescence. It’s really, really hard finding a rock of this size with the specs you provide in my budget range; most stretch it by another 10k-15k or so.
This one hits all the criteria you mention, except the star facets are 45 instead of 50-55.
SKU 6Z079Z784
This one hits almost all the Whiteflash ACA criteria save for a crown angle of 35.5.
FYI I’ve requested ASET/IdealScope for these two and those are pending. Hopefully, they’ll become available.
You are having a problem finding a diamond because your budget is unrealistic if you expect top notch performance and eyecleanliness at 3 carat colorless ranges. Ditch the mediocre diamonds you chose.
If you want a well cut 3 ct diamond, these are 2 I would recommend instead:
SKU R307-0370235Z2
SKU R282-047839473
The first E color diamond is the one I would recommend for a colorless 3 carater. The second diamond has strong fluorescence and that’s the reason the price is driven down. If you don’t mind fluorescence, you must get them to do a check for milkiness. If it isn’t hazy, this is by far the BEST diamond to buy in the market.
Paul
Thank you for this website. I wanted to get your thoughts on the the below piece:
1.71 Carat, F Colour (My girlfriend is sensitive to this), VS1
Depth 62.2 %
Table 57 %
Crown Angle 36.0°
Crown Height 15.5%
Pavilion Angle 40.8°
Lower Half 75%
Girdle Medium to Slightly Thick, Faceted, 3.5%
https://www.gia.edu/report-check?reportno=5293477116
I appreciate the crown angle is outside the bands (which will lead to some light leakage) but want to know your overall thoughts/ comments if its a good diamond (albeit not perfect) or completely not acceptable.
Without seeing details on tangible cut data like the Idealscope or ASET, I cannot offer much advice on how the impact of crown angles will affect the diamond’s performance. The thing is, why should you settle for a diamond with mediocre performance when you can easily find well cut diamonds in the market?
Hey Paul,
My boyfriend surprised me recently and told me he was ring shopping, but before he takes the dive he wanted to make sure I loved the ring. This is a pretty big commitment/investment and I just wanted to get your expertise on this piece in particular. I compared it to your guide and it seems like most of the proportions don’t meet your criteria, which is why I don’t feel too confident. We are hoping to get the most bang for our buck, in this case $24k. Please let me know what you think and if we should keep looking. Thanks so much!
2.56 Carat, I Color , VVS2 Clarity, Very Good Cut
Depth 58.6 %
Table 62 %
Crown Angle 30.5°
Crown Height 11.0%
Pavilion Angle 41.6°
Pavilion Depth 44.0%
Lower Half 80%
Girdle Very Thin to Slightly Thick, Faceted, 3.5%
Cutlet Very Small
https://www.gia.edu/report-check?reportno=1172432483
If you already read the article and through all the other comments, I think you already know the answer and what I will say. This diamond is garbage tier quality and is absolutely mediocre in cut quality.
Hi Paul,
I find your site extremely useful. Thank you for all the information you provide!
I am seriously considering this diamond being offered through a local diamond importer:
https://www.gia.edu/report-check?reportno=2205279046
The price is ~7500. I do not need a D color (this is D) – I care most about maximizing light performance and size with an eye-clean diamond to go in a platinum solitaire setting (so not too low on the color scale). I’m curious about your assessment of this on paper? Unfortunately no high quality pics of the stone but it looked beautiful in person… granted no natural light. Also, I love the look of the crisp dark arrows I see in many online pictures but I’ve not seen that clear of a pattern in person yet – one dealer told me I need “spot lighting” for the arrows to show up black-ish instead of silvery or grey. Is this true?
Many thanks for your advice!
Nah. The dealer is bullshitting you and clearly have no knowledge of what they are doing or selling. The fact that they claim that special spot lighting is required for arrows to show up in black says that they don’t even have basic knowledge of how diamonds work or how light return is generated in diamonds. And as I have said over and over and over again in the comments as well as the write up, there’s nothing useful I can tell you from a grading report alone. You need the tangible data of the diamond to do a proper analysis.
Hi Paul,
I have been looking at several super ideal diamonds from various diamond wholesalers (1.5 carats, VVS1, E). I see a significant diamond with crown angle of 36.2% and all other measurements fall within the parameters you defined for super ideal. You had defined the crown angle to be in the range of 33.9% – 34.9% for super ideal diamonds. I was curious if these parameters may have changed? If not, do you feel a crown angle of 36.2% would have a negative impact on brilliance, Fire, Sparkle and contrast of a diamond. Would you still consider it super ideal or ideal. Also do you think a price of $19,000 US a fair price for a 1.5 carats, VVS1, E, triple X, no floursence, no cutlet, 3.5% girdle, super ideal diamond (except for crown angle of 36.2%), GIA certificate.
Thanks.
Raj
The fact that this diamond has an excessively high crown angle should be a warning sign to you and I think you are asking the obvious having read this article. The proportions and guidelines laid out are valid and the thing is, you can’t base the determination of a super ideal cut diamond by proportions and numbers alone. So what if the diamond has proportions within my guideline? It means nothing. You need to look at the tangible data and shop at the right places. But getting the proportions wrong for a start is something that will make me not waste time on this diamond if I were looking for a super ideal.
Hey Paul, I came across your website recently and have learned so much binge reading your articles. I wanted to say thank you the knowledge you are sharing is super enlightening as I am searching for a engagement ring diamond. I also went back to the diamonds I was “considering” looked at the GIA to see how they fall in line with your requirements. Depth and table I filtered down but the crown/pav angles were always out of range !
Hi Paul,
I recently discovered your website and have been reading up on all your articles. We just bought a 1.52 carat GIA triple excellent diamond from James Allen that seemed well cut based on other guides but doesn’t satisfy your more stringent parameters. Specifically, it has a table of 58 and a uniform slightly thick (4%) girdle, which I think you recommended avoiding in one of your comments here.
Depth 61.8%
Table 58%
Crown Angle 34.5°
Crown Height 14.5%
Pavilion Angle 40.8°
Pavilion Depth 43.0%
Star Length 50%
Lower Half 75%
Girdle Slightly Thick, Faceted, 4.0%
Culet None
This scored a 1.4 in HCA (excellent for light return, fire, and scintillation and very good for spread) and according to HCA, the crown/pavilion angles put it in the overlap between GIA Excellent and AGS 0.
We are still within the return window for James Allen and are wondering if the 58 table and uniformly slightly thick girdle mean it won’t perform well and need to be returned? The video on James Allen looked very nice to us and we are a bit attached to the diamond but would you be able to take a look and share your objective opinion? Many thanks!
https://www.jamesallen.com/loose-diamonds/round-cut/1.52-carat-e-color-vs2-clarity-excellent-cut-sku-11346491
https://www.gia.edu/report-check?reportno=1369809344
The slightly thick girdle is not an issue for a round cut diamond. In general, anywhere within the range of thin to medium to slightly thick girdle sizes is OK for a round cut diamond and doesn’t bother me. Now, in terms of cut quality, the table size is a tad larger than what I generally recommend but having looked at the video, I would say that this is a decently cut diamond with good light performance. The optical symmetry on the diamond (contrast patterning) is decent as well and I will not classify this as a bad stone. Can it be better? Yes, it can. You may want to look at the True Hearts range for better cut diamonds but in your case, there’s a bit of a hassle and emotional attachment. If you like the diamond, keep it and enjoy it.
Hi Paul,
We’re looking to buy a 5 stone anniversary ring,
Something like this https://www.bluenile.com/build-your-own-five-stone-ring/18k-white-gold-diamond-five-stone-ring_62542
Our total budget is 5000, so around 3500 for the stones. We’re leaning towards 1.5 carats but is okay with Slightly smaller size diamonds if more beautiful. On Blue Nile for this ring, we are able to choose between thousands of 5 stone choices. The choices all have links to 5 individual GIA reports, but only 360 images for 1 or 2 of the stones. Can you help us pick out a good choice, the best cut stone?
James Allen also offers something similar
https://www.jamesallen.com/wedding-rings/womens-anniversary/14k-white-gold-five-stone-shared-prong-contour-diamond-ring-150-ctw-f-g-vs1-vs2-item-66594
But there is no info on the individual diamonds and if the diamonds would be GIA certified.
White flash also offers something similar at 1.25ct https://www.whiteflash.com/wedding-rings/five-stone-shared-prong-diamond-wedding-band-615.htm
But they state the diamonds will not be AGI certified due to size.
Do you think Blue Nile is the best choice to go with here, and if so, which diamonds to pick? The link to pick the diamonds for the blue Nile ring is this https://www.bluenile.com/build-your-own-five-stone-ring/diamonds
Please let us know your thoughts,
Thanks!
Yang
Hi Paul, thank you so much for your article! I was looking for something to teach me about the proportion of diamonds. I actually just received 2 custom cut diamonds (intending to make them into a pair of earrings). It seemed like the 0.388ct one is in better proportion. However, I have one question. What do you mean by girdle thickness (T – M – ST). Mine is Thin – Medium, not sure how this will impact the diamond. Do you think I should just keep the 0.388ct and reject the 0.381ct?
https://agslab.com/ym-vdgr/en-us/diamonds/104113632012/grading-report
https://agslab.com/ym-vdgr/en-us/diamonds/104114149054/grading-report
One more thing, I can’t seem to find the star facets and lower gridles in the AGS report. Don’t they usually show them on the report?
The star facets and lower girdle facet proportions are usually found in the proportions diagram for the standard ROUND CUT diamonds. These reports that you had linked to are for a modified round cut diamond. Even if you knew what these proportions are, it is meaningless. It doesn’t tell you how the diamonds will perform. Look at the tangible data. That is what matters and from what I can infer, these are both diamonds with strong light performance.
White Flash offers the best cut quality and if sparkle is what you are gunning for, go with White Flash. They should be able to allow a custom 5 ring head with the SAME design to accommodate 0.3ct stones.
Here are 5 well matched stones:
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-4311076.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-4361015.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-4361017.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-4361022.htm
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-4361012.htm
I can’t see the links to the diamonds on BN. You will need to give me the direct url listings to them but off hand, I can tell you that WF will beat BN in terms of quality. And price wise, it won’t be too much of a difference.
Hi Paul,
Thanks a lot for putting together this blog. I have a really good feeling I’ll be able to get a much better value for my money after reading your articles. I understand a lot of things now in theory, but I have zero practical experience. May I ask you to please take a look at this diamond and let me know what do you think?
https://www.bluenile.com/hu/diamond-details/LD15488030
I searched for one that is SI1, Excellent cut and colour I based on your blog and I tried to make sure it is eyeclean. I am a bit uncertain about the last part (i.e. whether it is eyeclean or not). I can see if there are no feathers, black dots, small scratches etc. I am however quite uncertain whether I should be picking a diamond only if it has visually zero of these and I am even more uncertain about whether it is cloudy/milky/hazy or not (I watched your comparison video on the latter topic but I couldn’t tell the difference there either). Thank you very much in advance!
Thank you
This diamond you picked out is hazy and cloudy due to the inclusions in it. It’s a terrible choice. You are choosing an SI1 diamond and if there aren’t visible inclusions under 10x magnification, that doesn’t mean you struck gold and found a nice diamond. Go think about it. If this is a flawless looking diamond, why on earth would GIA grade it as SI1? It’s graded as an SI1 rating because of the numerous small cloud inclusions present in the stone which don’t stand out but yet causes an impact on brilliance.
Hello,
I am currently looking at diamonds online at Brilliant Earth, and I have noticed that diamonds classified in their “True Hearts” range actually fall out of the specs you have listed above (two of them have a table size of 58% but are otherwise in range). Similarly, I have found a few diamonds that fall neatly into the range you specify but are not deemed “True Hearts”. I recognize the “True Hearts” moniker is mostly marketing, but the idealscope images on the website for diamonds outside of your specified range look very good, and yet the diamonds inside of this range do not look nearly as good.
As you might imagine I am a little confused. I have read your article about buying diamonds blind and have called Brilliant Earth to request the idealscope images of those outside the “True Hearts” lineup that meet your specifications.
Thanks!
The diamonds in the True Hearts collections are MARKETED for their superior light performance and cut precision. Compared to the other generic stuff you find in James Allen’s inventory, the True Hearts diamonds are generally much better cut. But are they ALL the best of the best? From experience, I can tell you that the curation standard at James Allen is good but NOT perfect. You will find truly well cut diamonds but there are less than ideal stones that fall through and get listed in that collection. To put a long story short, you need to know what you are doing to pick out the best stones.
The next point is, just because a diamond has good proportions doesn’t qualify it as beig well cut. Good proportions are just a pre-requisite as I had stated in this article. You Need tangible information like scope or video images to confirm light performance.
Hi Paul
Excellent article. I am looking at a diamond with the below report for a 3 carat round:
Depth 61.7%
Table 57%
Crown Angle 35.0°
Crown Height 15%
Pavilion Angle 40.8°
Pavilion Depth 43.0%
Star Length 45%
Lower Half 80%
Girdle Medium, Faceted, 3.5%
Culet None
Although the star length falls outside of your ideal proportions at 45%, do you think this completely rules out the diamond? Or is this fine and I should just order an ASET or ideal scope to confirm?
Thanks
The star facet length isn’t the biggest deal breaker here and tangible data like an ASET would still be required. The diamond could be good or could be a dud. You need scope images to help you decide which camp it falls into.
Hi Paul,
Thank you for putting together this information-its been like a bible to me.
If a stone is classified hearts and arrows say from IGI (which i know GIA to be superior) but I don’t have access to the aset images, etc…is that a better pick than one with the ideal dimensions you mentioned? I saw earlier you said you’d have to see it to confirm, but given that I can’t see them, would you gamble on dimensions or the IGI report saying hearts and arrows?
IGI’s classification of hearts and arrows is very broad and loose. Just like how a lot of jewelers classify their mediocre round cut diamonds as hearts and arrows, you need to rely on properly captured images to determine the cut precision. Having ideal proportions doesn’t mean the diamond is cut well. It’s just a prerequisite. If a vendor doesn’t offer the tangible information to you, then why on Earth would you want to buy from them when there are plenty of other vendors with transparent business practices.
Hi Paul,
Enjoying your website while searching for a diamond. I have 2 questions.
First, what does “lower girdles” refer to? I don’t typically see any measurement for that and from what I see anything referencing the lower girdle appears to be around 50% so I’m misinterpreting somewhere.
Second, how does one go about requesting an idealscope image? Is that something diamond jewelers have on hand or you have to request them and/or pay for them separately?
Thanks!
The lower girdle facets % can be found on the proportions diagram for a round diamond. If I understand you correctly, the 50% that you are referring to is the star facet length of the diamond. Again, this can be seen in the proportions diagram.
The idealscope image can be requested by asking your jeweler for it. This should be provided FREE OF CHARGE and is meant to help you assess the diamond’s light return. If they don’t or can’t provide them, then dump the jeweler and buy from one that provides it.