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Home > Diamond Education > Cut > Proportions Charts >


Proportions charts for Round Brilliant Cut

  Hearts & Arrows Ideal Cut American Ideal Cut International Fine Trade Cut US domestic Average Cut Below Average Cut
Cut classes Phenomenon Class 1A Class 1B Class 2A Class 2B Class 3A Class 3B Class 4A Class 4B
Table, %

53%-63% are weght specific in 1A, 1B, 2A grades
<=.49ct <=.49ct <=.49ct <=.49ct all weights all weights all weights all weights all weights
53-57.5 53-59 59.1-62
52.9-52
62.1-63
51.9-51.5
63.1-64
51.4-51
64.1-67
50.9-50.5
67.1-70
50.4-50
70.1-72
49.9-49
>72
<49
>=.50ct >=.50ct >=.50ct >=.50ct
53-58 53-58 58.1-60
52.9-52
60.1-63
51.9-51.5
Crown angle, ° 34.3-34.7 34.3-34.7 34-34.2
34.8-35
32.1-33.9
35.1-35.8
31.6-32
35.9-36.4
31.5-30.1
36.5-37.9
29.6-30
38-39.4
29-29.5
39.5-40.5
<29
>40.5
Crown height, % <=.49ct <=.49ct <=.49ct <=.49ct all weights all weights all weights all weights all weights
14-16.3 14-16.3 12.8-13.9
or
16.4-16.8
11.6-12.7
or
16.9-17.9
11.1-11.5
or
18.0-18.1
9.6-11
or
18.2-19.3
8.5-9.5
or
19.4-20.5
7.8-8.4
or
20.6-21.8
<7.8
or
>21.8
>=.50ct >=.50ct >=.50ct >=.50ct
14.3-16.3 14.3-16.3 13.5-14.2
or
16.4-16.8
11.6-13.4
or
16.9-17.9
Pavilion Depth, % 42.8-43.2 42.8-43.2 42.5-42.7
43.3-43.5
42-42.4
43.6-44
41.5-49
44.1-44.9
41-41.4
45-45.5
40.5-40.9
45.6-46
38-40.4
46.1-48
<38
>48
Girdle Thikness, %

Word description and percentages
Thin, Medium, Slightly thick
1.7-3
Slightly thin to slightly thick
1.5-4.5
Thin to slightly thick
1-4.5
Thin to thick
1-5.5
Very thin to very thick
0.4-7
Extra thin to extra thick
0-7
Total Depth, %

Determined by factors already considered above
58.7-62.3 58.7-62.3 58.3-58.69
62.31-62.99
57.9-58.29
63-63.5
57.5-57.89
63.51-63.8
57-57.46
63.81-64.1
56.5-56.99
64.11-65
55-56.49
65.1-67
<55
>67
Polish/Symmetry Excellent Excellent or Very Good Excellent to Good Good or Fair Poor