Diamond cut grades are based on the table and depth percentages of a diamond. In addition, there are evaluations or grades for the following:

• Table percentage (ratio of the table diameter to the overall diameter)
• Depth percentage (ratio of the depth to the diameter)
• Crown height
• Crown angle
• Girdle thickness
• Culet size
• Pavilion angle
• Pavilion depth
• Symmetry (alignment of the facets)
• Polish (smoothness of the diamond's facets)
• Fluorescence

Ideal Proportions for Round Diamonds

Depth Percentage: 60.2% - 62.7%
Table Percentage: 53% - 57.0%
Girdle: Thin to medium
Culet: None to very small

Preferred proportions for oval, pear, marquise, and heart-shaped diamonds

Depth Percentage: 58.9% - 65.4%
Table Percentage: 53% - 64%
Girdle: Thin to thick

Preferred proportions for emerald & radiant cut diamonds

Depth Percentage: 59.9% - 69.0%
Table Percentage: 59% - 69%
Girdle: Thin to thick

Preferred proportions for princess cut diamonds

Depth Percentage: 64.0% - 75.0%
Table Percentage: 59% - 72%
Girdle: Thin to thick