What are the Perfect Diamond Cut proportions to maximize Sparkle?
Since cut is such a major topic in the diamond selection process it is estimated that 98% of the round diamonds are 
of lower cut quality. 

Why? A diamond’s price is most significantly affect and calculated by carat weight.
Cutters, polishers maximize carat weight instead of “sacrificing” weight for better cut.
The difference in price vary from minus 60% to plus 50%. A DIFFERENCE OF 110% !
Know all about here.
Find out how to evaluate diamond cuts here:

Diamond cutting & polishing is the art, skill and science of transforming a rough stone into a brilliant diamond.
'Cut' has two meanings in relation to diamonds. 
The first is the shape: round, oval and so on. 
The second relates to the specific quality of cut within the shape and the quality and price will vary very greatly based on the cut quality. 
Read more about at Wikipedia, the art of diamond cutting

Shape is the model or form of the diamond, such as round, oval, pear,  princess and more. 
Cut refers to proportions and the finish grade.

The cut is the most important element to reflect brilliance and is determinable by 3 separate descriptions:
The cut is the most important element to control brilliance, scintillation and fire.

How Diamond Cut Affects Beauty and Price: View the Quality variations chart

The sparkling quality of the cut is to be determined by 3 separate factors:

1. Proportions
2. Polish
3. Symmetry

What are ideal cut diamonds

Important notice
if yo do not want to get crazy to find out the best cut by yourself...
If you are not a professional or familiar with the cut grading, 
trust the independent, best Gemological Laboratory:
Inspect the diamond loose and its genuine grading document 
at the diamantaire.

The trustworthy grading and Diamond Certificates are mostly from:
HRD – Diamond High Council of Antwerp World Diamond Center (non profit!)
IGI – International Gemological Institute View Diamond Certificate
GIA – Gemological Institute of America

How Diamond Laboratories grade Cut: Proportions - Polish - Symmetry

1. Proportions
Too shallow and / or too deep cut diamonds will loose brilliance through the side and bottom. 
The result is a dull diamond with less brilliance, affecting the ultimate value in terms of quality and price!
Excellent, Very Good, Good, Fair, Poor or Unusual

2. Polish
Finish grade or polish for ideal cut diamonds are described as following:
All facets of a diamond are carefully polished to eliminate all imperfections, characteristics such as abrasions, 
scratches, nicks and polishing marks on the surface of the diamond to give the mirror shine and the final beauty touch.
Polish grading: Excellent, Very Good, Good, Fair, Poor or Unusual

3. Symmetry
is the balance and regularity / evenness of facets.
Facets are compared in opposing pairs, defined  as following: 
Symmetry grading: Excellent, Very Good, Good, Fair, Poor or Unusual

Triple Excellent cut
When proportions, Polish and Symmetry are graded Excellent it is named Triple Excellent

Ideal cut = Perfect cut = Triple Excellent + Hearts & Arrows = Best Value! 
When Proportions, Polish, Symmetry are graded Excellent

4. Hearts and Arrows - The Top in the Art of cutting read all about. 

Measurements for Round Brilliant diamonds Measurements of fancy cut diamonds

I repeat once again: 
if you do not want to get crazy to find out the best cut by yourself's... If you are not a professional or familiar with the cut grading, trust 
the independent Grading by a reputable GIA, HRD or IGI Gemmological Laboratory. Best view the diamond loose and its genuine grading document 
at the diamantaire.
If you are not sure, trust the opinion of the Expert, the independent Grading by a reputable Gemmological Laboratory!

Proportions:                   Total depth %           Table %              Crown %        Crown angle °    Pavilion %         Pavilion angle °

Excellent:                          58.0 - 63.5               52.0 - 63.0         12.0 - 16.5       31.5 - 36.5        42.0 - 44.5        40.0° - 41.7°

Very Good:                        55.0 - 65.5               52.0 - 66.0         10.0 - 17.5       28.5 - 38.0        41.5 - 45.0        39.7° - 42.3°

Good:                                53.0 - 69.0               50.0 - 70.0          8.5 - 19.0        26.0 - 40.0       41.0 - 46.5        39.4° - 42.9°

Fair & poor:                       less than                  less than            less than         less than         less than           less than

Girdle thickness:

Thin to slightly thick is OK
diamond proportions measurements picture
100 %
Total depth 58.0 - 63.5 %
Ideal Table size 52.0 - 63.0 %
Crown depth12.0 - 16.5 %
Crown angle 31.5 - 36.5°
Pavilion  hight 42.0 - 44.5 %
Pavilion angle 40.0° - 41.7°
Cullet: pointed 0 - 1 %
Girdle thickness: 1.8 - 2.0 %
Approximate ideal proportions for fancy shapes:
Please note that there are no ideal proportions for fancy shapes: they are fancy!

Shape           ideal length          width 

Oval             1.30 to 1.68          1.00 

Marquise    1.75 to 2.25          1.00 

Princess     1.00 to 1.10          1.00 

Pear             1.50 to 1.75          1.00 

Heart            1.00 to 1.10         1.00 

Emerald      1.50 to 1.75          1.00

The depth percentage of an fancy cut diamond is generally determined by dividing the length to width ratios
Ideal Diamond Proportions
 Email     Tel: +32 3 233 29 90 
Antwerp World Diamond Centre, Diamond Exchange, Hoveniersstraat 2, Antwerp / Belgium / Europe
This page was last updated on: August 9, 2018
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analysis of your needs
Cut quality is the missing link on Rapaport prices , now completed here.

This is the reason why you can get from -60% discount to +50% premium on prices!
Ideal or excellent cut diamonds are premiums.

The proportions, glitter, brightness or brilliance and beauty are realized by ideal proportions, symmetry and cut 
of Table, Crown hight, Pavillion and Cullet. 
why diamond cut is most important within the 4C's
H&A diamond image view from top of table
Learn in One Minute all about diamonds: Diamond Course for Free for starters.
No need to become an expert. 
Trust the results of the Grading Labs GIA and HRD. Everything is mentioned on the certificate. 
We only show you details of cut to understand how it is working: