Best Proportions in a Fancy Shape Diamond – Oval, Cushion Cut, Emerald Cut, Pear Shape, Radiant Cut, Princess Cut
The best answer to the question of “What are the best proportions of a fancy shape diamond (the generic term for an Oval, Cushion Cut, Emerald Cut, Pear Shape, Radiant Cut, Princess Cut, among others) is that there is not any best proportion. No laboratory assigns a grade for the proportion of a fancy shape diamond. Moreover, there are no scientific parameters for determining what is or is not the “proper” dimension or ratio of any particular fancy shape diamond
The idea of what is “best” in regard to proportion is somewhat like asking “What should a beautiful woman look like?”. Everyone has there own idea of beauty. It is something that cannot be put on paper with any degree of authority. At best, we can perhaps come up with a “range”. Even then, we must assume that there will always be a multitude of exceptions – whether it be a beautiful woman or a diamond. Some are truly beautiful despite being different from our preconceived notions or parameters.
Perhaps the best guide that we have in determining what are “proper” or “best” proportions is to utilize the “calibrated” sizes and their corresponding ratios of semi-precious stones – such as Amethyst or Blue Topaz. Unlike diamonds that are often cut with regard to the “rough” diamond, semi-precious stones (because of the lack of concern about weight loss) are cut to calibrated sizes that have endured through time – whether it be an Oval, Emerald Cut, Pear Shape, or other shape.
Additionally, my 40+ years of working within the diamond trade has given me a thorough understanding of what dimensions are most desirable and advisable. Even with such an understanding, one must understand that often the proper dimensions or ratio will change depending on the type of mounting that will be utilized in setting the diamond. For instance, it is my experience that a three-stone ring may often look better with a longer Emerald Cut that that which might be in a plain “solitaire” mounting or in a classic “Tapered Baguette” mounting. Furthermore, a “Halo” style may require something different from either of the above mounting styles.
Before continuing, I have one very important bit of advice. It is not advisable to purchase a fancy shape diamond simply based upon dimensions or ratios or any other descriptive element contained on a GIA grading report! I see hundreds of diamonds every week. The information that is contained within the grading report has almost nothing to do with the overall beauty of the diamond! This is something that must be observed with you eyes -preferably live and in person – or at least in a photograph. To make you purchase decision based solely on a paper report is setting yourself up for disappointment.
AND now for my suggested parameters: . . .
OVAL Diamond Proportions: The standard calibrated ratio of Ovals is approximately 1.25 : 1 to 1.40 : 1. In other words, standard calibrated sizes will be 8x6mm or 9x7mm or 10x8mm. In my own experience, this ratio range seems to be the “proper” proportion. While I would not suggest going much below 1.20 : 1 (a slightly shorter and wider dimension), some people may prefer a somewhat longer length : width ratio. I would consider going up to a ratio of 1.50 : 1. This, however, is considered long and must be taken into consideration with many other factors of the diamond.
The 2.02 carat Oval pictured here measures 9.15 x 6.82mm. The ratio is 1.34 :1.
EMERALD CUT Diamond Proportions: The calibrated sizes for Emerald Cut diamonds is basically the same as that for Ovals. The ratio is approximately 1.25 : 1 to 1.40 :1. Again, this ratio may be somewhat less (like 1.20 : 1), however a longer Emerald Cut may be preferred.
A ratio of 1.55 : 1 is close to the maximum range that I would recommend for anyone who is seeking a “long” Emerald Cut shape. One must be aware, however, that it is somewhat difficult to find a “long” emerald cut that is lively and bright and “well-cut’.
The 1.28 carat Emerald Cut picture here measures 6.97 x 5.51mm. The ratio is 1.27 : 1.
A ratio of 1.50 : 1 is often referred to as a “credit card” shape as these dimensions are represented by any standard credit card.
ASSCHER CUT Diamond Proportions: An Asscher Cut diamond is basically a square Emerald Cut. A ratio of 1.05 :1 or less is most preferred. It is important top note that GIA will designate Square Emerald Cut within this ratio. A ratio of up to 1.10 : 1 will still appear square when set into a mounting, although this ratio may be discounted more than the 1.05 : 1 ratio as the GIA designation will not designate “Square”. The ratios between 1.10 and 1.20 : 1 is the “lost” area between Emerald Cut and Asscher Cut and are usually less desirable and less expensive..
This 3.00 carat Asscher Cut diamond measures 7.83 x 7.62mm. The ratio is 1.03 :1.
CUSHION CUT Diamond Proportions: The Cushion Cut has become the “IT” diamond shape over the past several years – replacing the Princess Cut as the “hot” non-round brilliant shape. I personally think that this is for good reason as a Cushion Cut combines the brilliance of a round diamond with a somewhat square shape. For this reason GIA refers to this shape as a “Cushion Modified Brilliant” or “Cushion Brilliant”.
There is no preferred length by width ratio for a Cushion Cut diamond. Most Cushions are somewhat square in dimensions. Others may be somewhat rectangular, although it is extremely difficult to find a Cushion Cut that is of the rectangular dimensions of an Emerald Cut or Oval.
The 5.00 carat Cushion Cut diamond pictured here measures 10.5 x 9.29mm. The ratio is 1.11 : 1.
Cushion Cut diamonds, more so than any other shape, can be exceptionally beautiful or not pretty at all. It is not a question of dimensions that make a Cushion Cut beautiful; it is a question of the overall shape and faceting – none of which is characterized by any information on a GIA grading report, including the Polish and Symmetry grades. Cushion Cut diamonds must be purchased based on their actual appearance. To purchase a Cushion Cut in any other way will lead to serious disappointment. (For more insight, please see my post Buying a Fancy Shape Diamond – BUYER BEWARE!
RADIANT CUT Diamond Proportions: A Radiant Cut diamond is, in many ways, similar to a Cushion Cut when it comes to dimensions. There is no clear cut or “proper” length by width ratio. Radiant Cuts can be squarish or they can be somewhat rectangular. Some may be as rectangular as a long Emerald Cut. Most Radiants tend to be squarish; rectangular Radiant Cuts are much more difficult to locate.
The 2.54 Carat Radiant Cut pictured here measures 8.53 x 7.10mm. The ratio is 1.20 :1. This is a beautiful “rectangular” Radiant Cut.
Like most fancy shape diamonds, the beauty of this pictured Radiant Cut diamond is not the result of any characteristics noted on the grading report. It is simply a matter of beautiful faceting which has nothing to do with the Polish or Symmetry grades as noted on the certificate. For more information on this subject, please see my post Excellent Cut in a Fancy Shape Diamond – Oval, Cushion Cut, Emerald Cut, Pear Shape, Radiant Cut, Princess Cut