Cut Grading Across Diamond Shapes
Cut grading only tends to be provided for Round diamonds. This is because it is extremely difficult to assess the ideal proportions of the likes of Marquise and Cushion. However, there are some experts that have done research about the ideal proportions for these shapes, and thus we will provide you with a small guide below.
In short: GIA assigns formal cut grades (Excellent → Poor) only to round brilliants — fancy shapes (oval, princess, emerald, cushion, marquise, pear, heart, radiant, Asscher) carry no official cut grade because optimal proportions vary by silhouette. Judge fancy cuts by length-to-width ratio, light-return symmetry, bow-tie severity in elongated cuts, and table-to-girdle alignment. Polish and symmetry grades still appear on every certificate.
Step Cuts
(Asscher and Emerald)
Excellent
Depth percentage – 58 - 65
Table percentage – 60 - 65
Very good
Depth percentage – 55 – 70
Table percentage – 59 - 70
Good
Depth percentage – 52 - 75
Table percentage – 52 - 75
Excellent
Depth percentage – 58 - 65
Table percentage – 60 - 65
Very good
Depth percentage – 55 - 70
Table percentage – 59 - 70
Good
Depth percentage – 52 - 75
Table percentage – 56 - 75
Modified Brilliant Cut Diamonds
(Pear, Princess, Marquise, Radiant, Oval, and Heart)
Here is a guide to the depth percentage and table percentage you should be looking for in regards to each of the sought after grades.
Excellent
Depth percentage – 58 - 64
Table percentage 55 - 62
Very good
Depth percentage – 57 - 66
Table percentage – 53 - 64
Good
Depth percentage – 56 - 68
Table percentage – 52 - 65
Excellent
Depth percentage – 62 - 73
Table percentage - 57 – 72
Very good
Depth percentage – 60 - 77
Table percentage – 55 - 75
Good
Depth percentage – 57 - 83
Table percentage – 52 - 85
Excellent
Depth percentage – 58 - 64
Table percentage – 55 - 62
Very good
Depth percentage – 57 - 66
Table percentage – 53 - 64
Good
Depth percentage – 56 - 68
Table percentage – 52 - 65
Excellent
Depth percentage – 52 - 60
Table percentage – 55 - 62
Very good
Depth percentage – 50 - 62
Table percentage – 50 - 62
Good
Depth percentage – 45 - 65
Table percentage – 52 – 65
Excellent
Depth percentage – 58 - 64
Table percentage – 55 - 62
Very good
Depth percentage – 57 - 66
Table percentage – 53 - 64
Good
Depth percentage – 56 - 68
Table percentage – 52 - 65
Excellent
Depth percentage – 62 - 68
Table percentage – 58 - 65
Very good
Depth percentage – 58 - 70
Table percentage – 56 - 70
Good
Depth percentage – 57 - 75
Table percentage – 54 -75
Round Brilliant Cut
This is the most brilliant of all the diamond cuts. Here is a guide to the depth percentage and table percentage you should be looking for in regards to each of the sought after grades.
Excellent
Depth percentage – 60 - 63
Table percentage – 53 – 58
Very good
Depth percentage – 58 - 64
Table percentage – 52 - 62
Good
Depth percentage – 56 - 67
Table percentage – 50 - 67