Diamond Proportions

THE IDEAL CUT

When a round, brilliant diamond has been cut to “Ideal” proportions by a master cutter, it has a splendor to behold.

The Ideal Cut Diamond describes a round brilliant diamond that has been cut to exact mathematically proven proportions. Its symmetry, with 58 exactly placed facets, produce the ultimate in lustre and beauty.

When a diamond is cut to ideal proportions, all of the light entering from any direction is totally reflected through the top and is dispersed into a display of sparking flashes and rainbow colours.

diamond proportions

THE PREMIUM CUT

A Premium Cut diamond demonstrates subtle variations from the Ideal Cut. Although dimensional differences affect a diamond’s reflection of light, a Premium Cut still achieve a harmonius balance between its proportions and the display of brilliance

diamond proportion

Preferred Proportions for Round Diamonds

Ideal Proportions Acceptable
Depth Percentage:  60.2% – 62.7% 57.0% – 64.0%
Table Percentage:  53% – 57.0% 53.0% – 64.0%
Polish: Very Good to excellent Good to Very Good
Symmetry: Very Good to excellent Good to Very Good
Girdle: Thin to medium Thin to Thick
Culet: None to very small None to medium

Preferred Proportions for Oval, Pear, Marquise, and Heart-Shaped Diamonds

Depth Percentage:  58.9% – 65.4%
Table Percentage:  53% – 64%
Polish: Good to excellent
Symmetry: Good to excellent
Girdle: Thin to thick

Preferred Proportions for Emerald and Radiant Cut Diamonds

Depth Percentage: 59.9% – 69.0%
Table Percentage: 59% – 69%
Polish: Good to excellent
Symmetry: Good to excellent
Girdle: Thin to thick

Preferred Proportions for Princess Cut Diamonds

Depth Percentage: 64.0% – 75.0%
Table Percentage: 59% – 72%
Polish: Good to excellent
Symmetry: Good to excellent
Girdle: Thin to thick