The depth of a diamond is the distance between the table facet and the culet measured in millimeters. The depth of a diamond is expressed in percentages.

Mathematician and gem enthusiast Marcel Tolkowsky (who developed the round brilliant cut) defined the ideal dimensions as:

  • Table percentage (table diameter divided by overall diameter) = 53%
  • Depth percentage (overall depth divided by the overall diameter) = 59.3%
  • Pavilion Angle (angle between the girdle and the pavilion) = 40.75°
  • Crown Angle (angle between the girdle and the crown) = 34.5°
  • Pavilion Depth (depth of pavilion divided by overall diameter) = 43.1%
  • Crown Depth (depth of crown divided by crown diameter) = 16.2%

Blue Nile‘s  Round Cut Grading Proportions

AGSL cut grading criteria

Cut Grade Depth % Table %
Signature Ideal 60.1 – 61.9 55 – 57
Ideal 60.1 – 62.8 53 – 57
Very Good 58.5 – 64 52 – 60
Good 57.5 – 64.5 51 – 65
Fair 56.5 – 67 50 – 67
Poor <56.5 or >67 <50 or >67
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