AGA Round Brilliant Cut Grading Chart

The tables below show the AGA Cut Grading system for round diamonds developed by D. S. Atlas and his laboratory Accredited Gem Appraisers. This system has been adopted by the National Association of Jewelry Appraisers (NAJA).

CUT CLASSES

Class1A

Class1B

Class 2A

Class 2B

 

American Ideal Cut

International fine trade cut

Table %

53-58%

52-60%

51.5-63%

51-64%

Crown angle°

34.0-34.7

33-35.1

32.1-35.8

31.6-36.4

Crown height %

14-16.3%

13.5-16.8%

11.6-17.9%

11.1-18.1%

Pavilion Depth %

42.8-43.2%

42.5-43.5%

42-44%

41.5-44.9%

Girdle Thickness:
Word descriptions

Thin to Medium (1.0% to 3.0%)
Medium to Slightly thick (1.7% to 4.5%)

Very thin to Slightly thick (0.4% to 4.5%)
Thin to Slightly thick (1.0% to 4.5%)

Very thin to Slightly thick (0.4% to 4.5%)

Very thin to Thick (0.4% to 5.5%)

Total depth %

Determined by
factors already
considered above

58-62.3%

58.3-62.99%

<58.3%
>63%

Polish/Symmetry

NOT A PRIMARY
DETERMINING
FACTOR

Excellent -Very Good

Excellent toGood


CUT CLASSES

Class 3A

Class 3B

Class 4A

Class 4B

 

US domestic average cut

below average

Table %

50.5-67%

50-70%

49-72%

>72%
<49%

Crown angle°

30.1-37.9

29.6-39.4

29-40.5

<29
>40.5

Crown height %

9.6-19.3%

8.5-20.5%

7.8-21.8%

<7.8%
>21.8%

Pavilion Depth %

41-45.5%

40.5-46%

38-48%

<38%
>48%

Girdle Thickness:
Word descriptions

Very thin to Very thick (0.4% to 7.0%)

Extremely thin to Extremely thick (0.0% to >7.0%)

Total depth %

<58.3%
>63%

Polish/Symmetry

NOT A PRIMARY
DETERMINING
FACTOR

Good -Fair

Poor

 

A diamond called a "Tolkowsky Cut" is only approximated by cut 1A. However, a "Tolkowsky Cut" is a very specifically calculated cut with the following parameters:

Table 53.0%, Crown Angle 34.6, Crown Height 16.2%, Girdle Thickness app 1.7%, Pavilion Depth 43.1%. Many diamonds are improperly called "Tolkowsky Cut" when they are only approximating the parameters Tolkowsky formulated.

Courtesy of D.S. Atlas, Accredited Gem Appraisers, © AGA 1998-2004



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