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Home >> Diamond Grading >> Diamond Shapes >> Diamond Cut >> Ideal Cut

No formal work on the relationship between optics and diamond cutting appeared until the twentieth century. Then, much later, in 1919 Marcel Tolkowsky -- a member of a Belgian cutting family-- published a short paper entitled Diamond Design. This was the first analysis of diamond cutting design based on modern scientific theories of light behavior. Although Diamond design was first published in England, Tolkowsky’s design is often called the “American Ideal” because U.S. Cutters were the first to produce it in significant quantities.

In the 1950’s AGS adopted Tolkowsky’s model as its standard for grading cut. The only modification to the basic design were establishing limited ranges for table size, crown height, pavilion depth and girdle thickness. In 1995, the updated model was renamed the AGS Ideal Cut. The demand for diamonds cut according to the AGS Ideal has increased substantially, and today numerous cutters are producing designs

The AGS Ideal 0 Cut grade represents the very best in diamond cutting: AGS 0 is only assigned to a diamond in which correct proportions, precise symmetry, and fine polish are combined to produce an optimum display of brilliance, scintillation and dispersion. The impression is a harmonious balance between the physical dimensions of the diamond and the optical components of its beauty.

As diamond fall into grades further from 0, their relative beauty begins to diminish, For example, a diamond with a cut grade 1 is very close to 0 in appearance. A cut grade of 2 is still considered to have very fine proportions and deliver exceptional brilliance.

A cut grade 5 diamond has variations that detract significantly from overall appeal. It may appear somewhat “washed out or slightly dark through the center. Cut grade 10 diamonds have, the worst examples of proportioning, symmetry, and polish, so  they have little visual life.
Quick Reference Diamond Cut
Round Diamond
Ideal Cut - AGS 0
Very Fine Cut - AGS 2
Depth %
59% - 63%
59% - 63%
Table %
52.4% - 57.5%
51.4% - 62%
Girdle Thickness
Thin to Medium
Very Thin - Thick
Cullet Size
None - Medium
None - Medium
Excellent to Good
Excellent to Good
None to Faint
None to Faint
Length to Width Ratio
1 to 1
1 to 1
Crown Angle
33.7% - 35.8 Degrees
32.2 - 36.8 Degrees
Crown Height
15% - 16.2%
13.1% - 16.2%
Pavilion Angel
40.5 - 41 Degrees
39.7 - 41.7 Degrees
Pavilion Depth %
42.2% - 43.8%
41.7% - 44.8%
pad AGS Guidelines

Home >> Diamond Grading >> Diamond Shapes >> Diamond Cut >> Ideal Cut