(Scroll down for our 60,000 diamond Search Engine.)

Diamond Cut Grading Simplified

Diamond Cut Grading is the most important factor for diamond beauty. It produces the sparkle.

A rough diamond looks like any other rock until it is "cut" into many facets at optimum angles to produce maximum brilliance (sparkle) and fire (reflected colors). The quality of the cut is known as the "make".

In 1919 Marcel Tolkowsky developed the formula for the perfect round brilliant cut which has become the premium or "ideal" cut for round diamonds. Since then there have been various modifications and disagreement over what constitutes the true "ideal" cut for diamond cut grading.

However, the Gemological Institute of America (GIA) has developed the following guidelines for grading the make of round brilliant cut diamonds only.

The "Table Size %" is the ratio of the table diameter to the girdle diameter. The "Depth %" is the ratio of the distance between the table and the culet to the girdle diameter. These are the two most important factors in determining a diamond'a cut grading level.

This is the factor that contributes the most to a diamond's beauty. Even if a diamond is brownish and has visible inclusions, if it sparkles well it is a thing of beauty.

(NOTE: To better understand Diamond Cut Grading use the Search Form below, from time to time, to do a trial search of our 60,000+ Diamond List and compare the pricing of various diamond grades.

Print the tables below and use them to find a diamond with a Class 1 or at least a Class 2 Cut grade and you won't go wrong.

KEY FACTORS	Class 1 Premium Cut	Class 2 Well Cut	Class 3 Cut Average	Class 4 Cut Below Avrg
Table Size	53-60% of diameter	61-64%	65-70%	over 70%
Depth	58-63% of diameter	57-64%	56-66%	under 56% over 66%
Crown Angles	34-35 degrees	32-34 degrees.	30-32 degrees	less than 30 degrees
Girdle Thickness	medium - slightly thick	thin-thick	thin or very thick	knife edge or very thick+
Polish & Symmetry	very good - excellent	good	fair	poor

More detailed charts were developed by David Atlas for Diamond Cut Grading of fancy cut diamonds (other than round) and are used by Accredited Gem Appraisers, D. Atlas & Company, Inc. and the National Association of Jewelry Appraisers. Simplified versions for these charts are shown below. (Revised: 3/02)

Princess Cut Diamonds

KEY FACTORS	Class 1 Cut Premium	Class 2 Cut Fine Trade	Class 3 Cut Average	Class 4 Cut Below Avrg
Table Size	60%-71% of diameter	58%-77%	53%-85%	Below 53% Above 85%
Depth	64%-75% of diameter	58%-80%	56%-84%	Below 56% Above 84%
Crown Height %	8.5%-11%	6.0%-13%	4.0%-17.5%	Below 4.0% Above 17.5%
Girdle Thickness	thin-med or med.-thick	thin-thick	very thin - very thick	extra thin - extra thick
Polish & Symmetry	good - excellent	fair -good	fair-good	poor to fair

Pear, Marquise, Heart, and Oval Cut Diamonds

KEY FACTORS	Class 1. Premium Cut	Class 2. Fine Trade Cut	Class 3. Average Cut	Class 4. Below Average
Table Size	54%-61.5% of diameter	52%-64%	50%-70%	Below 50% Above 70%
Depth	59%-63% of diameter	58%-65.4%	46%-71%	Below 46% Above 71%
Crown Height %	12.5%-15%	11.1%-16.5%	8.7%-18.4%	Below 8.7% Above 18.4%
Girdle Thickness	thin-med. or med.-thick	thin-thick	very thin to very thick	extra thin to extra thick
Polish & Symmetry	good to excellent	good to excellent	good to fair	fair to poor
Length: Width Ratios	Class 1 & 2 Pr. 1.5-1.75 M.1.75-2.25	Class 1 & 2 Ht..98-1.02 O.1.33-1.66	Class 3 & 4 Pr.1.26-1.99 Mr.1.51-2.49	Class 3 & 4 Ht.0.91-1.24 Ov.1.26-1.74

Emerald and Radiant Cut Diamonds

KEY FACTORS	Class 1. Premium Cut	Class 2. Fine Trade Cut	Class 3. Average Cut	Class 4. Below Average
Table Size	60%-64.1% of diameter	58%-69%	53%-76%	Below 53% Above 76%
Depth	60%-65% of diameter	58%-69%	56%-78%	Below 56% Above 78%
Crown Height %	11.9%-15%	11.1-16.2%	8.5%-18.5%	Below 8.5% Above 18.5%
Girdle Thickness	thin-med or med.-thick	thin-thick	very thin to very thick	extra thin to extra thick
Polish & Symmetry	good - excellent	fair-good	fair-good	poor to fair
Length-Width Ratios	Emerald Cut: 1.26-1.99

There are other grading systems such as "A, B and C" and a large variety of opinions that align loosely with the above charts.

We have used diamond appraisers manuals to prepare these charts, so consider them accurate.

Recently, GIA has started putting the diamond cut grade or "make" for round brilliant cut stones on their certificates. For other shape diamonds or certificates without diamond cut grading included, use the tables above to ensure you get a good looking one.

After having read about Diamond Cut Grading, go next to Diamond Caret Grading.

If you have any questions, email them to us at Diamond Search , or telephone 800-498-7302.