Tolkowsky’s Model of the Ideal 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.

the tolkowsky model of ideal cut

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.

If cut quality and the sparkle factor of a diamond matters to you, I recommend that you visit White Flash and Brian Gavin Diamonds. They offer the best cut quality diamonds in the world and a wide range of high quality engagement ring settings.

General Ideal Proportions For Round Brilliant Cut

For the modern day shopper, scroll downwards and use MY curated list of proportions instead.

  
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: This table should be used as a reference only.

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 widely accepted that an ideal cut could have proportions which fall within certain values and diamonds with bigger tables can also achieve ideal optical properties.

Both GIA & AGS had also came up with comprehensive tables of proportions that “ideal stones” should have. You can download the AGS proportions chart 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. To save time and weed out the badly cut diamonds, I strongly recommend that you apply these parameters into your own diamond search.

super ideal round diamond proportions chart

Now, with all the technical specifications laid out, you might assume that all diamonds could be cut to ideal standards if cutters simply follow the formulas. 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.

Read on to find out why such a phenomenon exists in the industry…

As a consumer, let me tell you that I’m super anal about cut quality when I purchase a diamond. White Flash and Brian Gavin Diamonds are reputable companies who offer diamonds that meet my standards for being truly well cut. Check them out for yourself!

Next Page >>

Related Articles

Sharing Is Caring ! Share on Facebook0Share on Google+0Tweet about this on TwitterShare on LinkedIn0Share on Reddit0Share on StumbleUpon0

106 Comments

  1. Jenn-
    September 22, 2015 at 4:37 am

    Hi Paul,
    Per your ideal proportions, 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%).

  2. Paul Gian-
    September 22, 2015 at 2:38 pm

    A pavilion angle of 41.2° will almost always result in light leakage under the table.

  3. Jenn-
    September 23, 2015 at 2:59 am

    Thanks so much Paul! What impact does the crown angle of 35.5% have?

  4. Paul Gian-
    September 23, 2015 at 4:31 am

    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.

  5. shamuel-
    October 5, 2015 at 2:58 pm

    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 this diamond will fall in line with your ‘cream of the crop’ cut diamonds?

    table: 57
    depth: 62.3
    crown angle: 35
    pavilion angle: 41
    girdle: medium – slightly thick (faceted) 4%

  6. Paul Gian-
    October 6, 2015 at 2:05 am

    You need scope images like ASET, idealscope and H&A to do that. Numbers don’t reveal much.

    http://beyond4cs.com/buying-diamonds-blind/

  7. Hoss-
    October 13, 2015 at 12:58 am

    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, 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.

  8. Paul Gian-
    October 13, 2015 at 4:29 am

    It is a bad idea to buy such a large sized diamond with low clarity ratings blind.

    You need to read this: http://beyond4cs.com/buying-diamonds-blind/

  9. Zach-
    October 25, 2015 at 4:56 pm

    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? I value your opinions and comments and I want to learn how to buy a diamond ring without getting duped.

    Many Thanks,
    Zach

  10. Paul Gian-
    October 26, 2015 at 1:11 am

    Crown angles are too steep and will result in light leakage. Keep it under 41.0 degrees. Follow this guide carefully; http://beyond4cs.com/step-by-step-guide/

  11. rave-
    January 13, 2016 at 1:04 am

    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?

    https://www.jamesallen.com/loose-diamonds/round-cut/1.11-carat-h-color-vs2-clarity-excellent-cut-sku-714133

    Many thanks!

  12. Paul Gian-
    January 13, 2016 at 5:58 am

    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.

  13. rave-
    January 14, 2016 at 2:55 am

    Thx for the reply Paul, would you say that the diamond you recommended close to their “true hearts” range?

  14. Paul Gian-
    January 14, 2016 at 1:08 pm

    Yes.

  15. Jake-
    January 14, 2016 at 9:01 pm

    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

  16. Paul Gian-
    January 15, 2016 at 1:18 am

    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.

  17. Yifang-
    January 24, 2016 at 3:36 pm

    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

  18. Paul Gian-
    January 24, 2016 at 4:15 pm
  19. david-
    February 9, 2016 at 6:11 pm

    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?

  20. Paul Gian-
    February 10, 2016 at 9:57 am
  21. Richard-
    February 11, 2016 at 7:05 pm

    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

  22. Paul Gian-
    February 12, 2016 at 4:04 am

    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

  23. Pat-
    March 2, 2016 at 6:43 pm

    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

  24. Patrick Johnson-
    March 3, 2016 at 12:36 am

    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. Is this a good buy?

    Thanks,

    Pat

  25. Paul Gian-
    March 3, 2016 at 12:47 pm

    Read these:

    http://beyond4cs.com/buying-diamonds-blind/
    http://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.

  26. Faab-
    March 3, 2016 at 10:47 pm

    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

  27. Paul Gian-
    March 5, 2016 at 12:53 pm

    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

  28. Kim-
    March 22, 2016 at 2:01 pm

    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.

  29. Paul Gian-
    March 23, 2016 at 1:33 pm

    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: http://beyond4cs.com/buying-diamonds-blind/

  30. Cathy-
    March 29, 2016 at 11:21 pm

    HI Paul,

    What do you think of this one? Table is bigger than what you recommended.

    http://www.briangavindiamonds.com/diamonds/diamond-details/1.245-i-vs1-round-diamond-ags-104074030059
    Thanks.

  31. Paul Gian-
    March 30, 2016 at 7:26 am

    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.

  32. Cathy-
    April 1, 2016 at 12:44 am

    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.

    Thanks

  33. Paul Gian-
    April 1, 2016 at 3:24 am

    No. It’s not a problem if the ASET checks out.

  34. Hermi-
    April 6, 2016 at 8:28 pm

    Hi Paul,

    I’m currently looking at a 0.5ct.round with the following proportions

    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

  35. Paul Gian-
    April 6, 2016 at 10:11 pm

    Proportions and dimensions look good on paper. Get scope images to reveal light performance and cut precision quality.

    http://beyond4cs.com/2014/12/aset-reference-charts/
    http://beyond4cs.com/hearts-and-arrows/

  36. Eva-
    April 6, 2016 at 10:26 pm

    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

  37. Paul Gian-
    April 7, 2016 at 2:41 am
  38. Eva-
    April 7, 2016 at 6:11 am

    Thank you so much, Paul!

    The certificate says it has internal graining. What does that mean? Would that be eye-visible? Also, it sais 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 doesnt seem any more brown to me than other dianonds though).

    Also after some more time I shortlisted these: https://www.jamesallen.com/loose-diamonds/round-cut/?CaratFrom=0.28&CaratTo=0.47&Color=K,J,I,H,G,F,E,D&Clarity=VS2,VS1,VVS2,VVS1,IF,FL&Cut=Ideal,Excellent&PriceFrom=200&PriceTo=460&ViewsOptions=Images

    Is the one you suggested first still the best of them?

    Thank you very much for your help!!! It is awesome! 🙂

  39. Paul Gian-
    April 7, 2016 at 11:57 am
  40. Eva-
    April 7, 2016 at 9:34 pm

    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?

  41. Paul Gian-
    April 8, 2016 at 2:44 am

    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.

  42. James-
    April 25, 2016 at 6:21 pm

    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

  43. Paul Gian-
    April 26, 2016 at 6:41 am

    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.

  44. April 26, 2016 at 11:24 pm

    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.

  45. Paul Gian-
    April 27, 2016 at 4:10 am

    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

  46. Kevin G-
    May 19, 2016 at 10:32 pm

    Hello Paul,

    What are your thoughts on the following.

    https://www.jamesallen.com/loose-diamonds/round-cut/1.01-carat-g-color-si1-clarity-excellent-cut-sku-1133614

    I am looking for a round diamond 1-1.1ct. Do you have any recommendations if this particular one does not look good to you.

    Thanks

  47. Kevin G-
    May 20, 2016 at 2:45 pm

    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.

  48. Paul Gian-
    May 21, 2016 at 6:31 am

    It’s a good stone.

  49. Han-
    June 3, 2016 at 7:55 pm

    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.

  50. Tony-
    July 12, 2016 at 1:27 am

    When you give your curated list of proportions, you do not mention Girdle Thickness or Culet Size. What ranges/values do you suggest for these characteristics?

  51. Paul Gian-
    July 12, 2016 at 1:56 am

    No culet. There’s a range of girdle thickness I would accept: thin – medium – slightly thick (*I would avoid diamonds that have a consistent “slightly thick” girdle across the board.)

  52. Kyle-
    July 22, 2016 at 4:35 pm

    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!

  53. Paul Gian-
    July 23, 2016 at 3:14 am
  54. Dave-
    July 27, 2016 at 6:06 pm

    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 guidelines 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

    My apologies if this is too much information. I appreciate your assistance and hope to hear from you soon! Thank you!

  55. Paul Gian-
    July 28, 2016 at 12:44 am

    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.

  56. Dave-
    July 28, 2016 at 6:09 pm

    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!

  57. Paul Gian-
    July 29, 2016 at 2:51 am
  58. Art-
    August 3, 2016 at 7:22 pm

    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

  59. Paul Gian-
    August 4, 2016 at 6:08 am

    The numbers look fine.

  60. Joshua Goldsbrough-
    August 4, 2016 at 9:34 am

    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 proportions ideally 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

  61. Adam-
    August 26, 2016 at 7:27 am

    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

  62. Paul Gian-
    August 27, 2016 at 6:11 am

    Do you have a url to view the diamond listing and video?

  63. Paul Gian-
    August 28, 2016 at 4:02 pm

    It’s a well cut diamond for light performance.

  64. Adam-
    August 29, 2016 at 7:18 am

    Thanks Paul. Anything else you’d call out or looks like a good diamond?

    Really appreciate your help! Your website has helped me tremendously.

  65. Paul Gian-
    August 29, 2016 at 8:28 am

    It’s a great diamond. Go for it!

  66. TL-
    August 29, 2016 at 12:14 pm

    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?

  67. Paul Gian-
    August 29, 2016 at 1:30 pm

    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

  68. Roy-
    September 8, 2016 at 3:16 am

    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

  69. Paul Gian-
    September 8, 2016 at 4:38 am

    The crown angles affect the dispersion of fire and brilliance. Both are mediocre diamonds I would never consider touching.

  70. Donna-
    October 5, 2016 at 3:16 am

    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.

  71. Pulkit-
    November 6, 2016 at 10:57 pm

    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 HCA score of 1.3 and 1.4 respectively. 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!

  72. Paul Gian-
    November 7, 2016 at 3:06 am

    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

  73. Paul Gian-
    November 13, 2016 at 5:18 am

    It’s a well cut diamond. Good find!

  74. Steven Uy-
    November 18, 2016 at 1:59 am

    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

  75. Steven Uy-
    November 18, 2016 at 12:28 pm

    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.

  76. Steven Uy-
    November 18, 2016 at 1:06 pm
  77. Paul Gian-
    November 18, 2016 at 1:47 pm

    This diamond is well cut as well. Good choice!

  78. Choon Liang-
    November 19, 2016 at 4:54 pm

    Hi Paul, would like to ask for your opinion. 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!

  79. Paul Gian-
    November 20, 2016 at 3:36 pm

    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.

  80. Choon Liang-
    November 20, 2016 at 6:29 pm

    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

  81. Boris-
    November 26, 2016 at 12:20 am

    Hello Paul,

    Before committing, please find below a diamond I am interested in, his HCA scores 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,

  82. Paul Gian-
    November 26, 2016 at 1:34 am

    It’s not a well cut stone. https://www.bluenile.com/diamond-details/LD07788469

    This would be a much better option.

  83. Heidi-
    December 21, 2016 at 2:45 pm

    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 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://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3735485.htm

    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%

  84. Paul Gian-
    December 23, 2016 at 8:57 am

    The diamond looks well cut. I would have preferred it if the table size was kept a tad smaller.

  85. Tom B-
    January 9, 2017 at 1:50 pm

    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

  86. Abrantes-
    January 30, 2017 at 7:23 pm

    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!

  87. Paul Gian-
    January 31, 2017 at 2:47 pm

    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.

  88. Mike D-
    January 31, 2017 at 8:09 pm

    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!

  89. Paul Gian-
    February 1, 2017 at 2:56 pm

    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

  90. Ernest-
    February 2, 2017 at 8:21 pm

    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

  91. Matt-
    February 3, 2017 at 3:18 pm

    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

  92. Paul Gian-
    February 4, 2017 at 12:09 pm

    If cut quality matters, the table and depth proportions for this diamond will instantly make me reject this option out of the door.

  93. Rich-
    February 14, 2017 at 1:12 am

    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, 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

  94. Paul Gian-
    February 14, 2017 at 9:15 am

    Yep, you are right. The crown angles are way too low.

  95. Stuart-
    March 1, 2017 at 2:24 pm

    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

  96. Paul Gian-
    March 2, 2017 at 1:23 am

    It’s an extremely well cut diamond for light performance and is eyeclean. Great find!

  97. Stuart-
    March 4, 2017 at 11:11 am

    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 tool 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

  98. Paul Gian-
    March 4, 2017 at 3:11 pm

    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

  99. Matt-
    March 12, 2017 at 6:10 am

    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.

    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

  100. Paul Gian-
    March 13, 2017 at 1:14 pm

    I would love to help. Please get in touch with me via email directly.

  101. Jack-
    April 6, 2017 at 6:02 pm

    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

    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

  102. Paul Gian-
    April 7, 2017 at 1:21 pm

    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?

Leave A Comment