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The American Gem Society (AGS) has developed a unique scale ranging from 0 to 10, with 0 being the best, in which to grade diamonds. One area of assessment which AGS specializes in is grading the cut and proportions of a round brilliant diamond. The following chart provides a detailed analysis of the AGS cut classification system.

AGS Cut Grade Reference Chart

Average Table
Diameter %
AGS Grade
46.3 and smaller
10
46.4 to 47.3
9
47.4 to 48.3
8
48.4 to 49.3
7
49.4 to 50.3
5
50.4 to 51.3
3
51.4 to 52.3
1
52.4 to 57.5
0
57.6 to 59.5
1
59.6 to 61.5
2
61.6 to 63.5
3
63.6 to 65.5
4
65.6 to 67.5
5
67.6 to 69.5
6
69.6 to 71.5
7
71.6 to 73.5
8
73.6 to 75.5
9
75.6 and greater
10
Average Crown Angle
Angle (degrees)
AGS Grade
28.3 and less
10
28.4 to 29.1
9
29.2 to 29.6
8
29.7 to 30.1
7
30.2 to 30.6
6
30.7 to 31.1
5
31.2 to 31.6
4
31.7 to 32.1
3
32.2 to 32.6
2
32.7 to 33.6
1
33.7 to 35.8
0
35.9 to 36.3
1
36.4 to 36.8
2
36.9 to 37.3
3
37.4 to 37.8
4
37.9 to 38.3
5
38.4 to 38.8
6
38.9 to 39.3
7
39.4 to 39.8
8
39.9 and greater
10
Pavilion Depth
Percent
AGS Cut Grade
39.4 and less
9 or 10
39.5 to 40.1
8
40.2 to 40.6
7
40.7 to 41.1
5
41.2 to 41.6
4
41.7 to 42.1
2
42.2 to 43.8
0
43.9 to 44.3
1
44.4 to 44.8
2
44.9 to 45.3
4
45.4 to 45.8
5
45.9 to 46.3
6
46.4 to 46.8
7
46.9 to 47.5
8
47.6 to 48.5
9
48.6 and greater
10
Average Girdle Thickness*
Thickness
AGS Grade
Extremely thin
7
very thin
4
thin
0
medium
0
slightly thick
0
Also Check:
Extremely thin at any point
3
Very thin at any point
1
Thick at any point
3
Very thick at any point
5
Extremely thick at any point
7,8,9,10

* Overall average
AGS Culet
Size
AGS Grade
Pointed
0
Very small
0
Small
0
Medium
0
Slightly large
1
Large
3
Very large
5
Extremely large
7,8,9,10

 

Note: Grade 4 may be achieved using Symmetry/Polish considerations
Polish & Symmetry
Characteristics
Grade
0
Extremely difficult to locate
under 10X
1
Very difficult to locate under 10X
2
Difficult to locate under 10X
3
Relatively easy to see under 10X, not visable to unaided eye
4
Easy to see under 10X, extremely difficult to see with unaided eye
5
Very easy to see under 10X, very difficult to see with unaided eye
6
Obvious to see under 10X, difficult to see with unaided eye
7
Relatively easy to see
with unaided eye
8
Easy to see
with unaided eye
9 - 10
Obvious to see with unaided eye

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