consumer guidance. we do not sell jewelry.

Guidelines for Selecting a Well-Proportioned Diamond

The tables that follow were created by David Atlas of Accredited Gem Appraisers (AGA), and can be used as a guide to "judge" the quality of cut for a given shape.

A few notes on using the tables:

  1. Only the most important cut characteristics & dimensions for each shape are listed. Be sure to read the rest of this tutorial for other important considerations.
  2. The terminology used in this table ("depth%", "table%", etc.) is defined and explained in throughout the rest of this tutorial.
  3. Don't be a perfectionist.  It is acceptable to purchase a diamond that rates "good" or even "fair/poor" on any category, as long as you are AWARE of what you're purchasing and understand the cost and quality tradeoffs.

AGA Rules For Determining "Overall" Cut Grade.

Contributed by David Atlas of Accredited Gem Appraisers. The AGA cut rules and charts are copyrighted by D. Atlas & Co., Inc., and are used by permission here.

1A grade:
All characteristics are best when 1A, but may include a single 1B characteristic. You pay a premium for this cut and you should insist on getting exactly what you are paying for.

1B grade:
All characteristics need to be all 1B or 1A to 2B. Only a single class 2 characteristic is permitted. The class 2 characteristic should be within 2% or 2 degrees of the 1B characteristic.

2A grade:
All characteristics need to be 2A or 1A thru 2B. Only a single 2B parameter is permitted and it must be within 2% or 2 degrees of the 2A characteristic. (crown angle degree rounds only)

2B grade:
All characteristics need to be all 2B or 1A thru 3A. Only a single 3A characteristic is permitted and the 3A characteristic cannot be a very thick girdle or more than 1 degree too shallow a crown angle. The 3A characteristic must be within 2% or 1 degree of the 2B characteristic. (crown angle degree rounds only)

3A grade:
A stone may be all 3A or 1A thru 4A. Any characteristics of 4A must be within 2% or 1 degree the 3B characteristic. More than a single 4A characteristic and the stone cannot grade 3A. More than two 3B characterisitics or a 4A plus a 3B also prevent a stone from grading 3A. Stones with class 4, extremely thick or extremely thin "overall" girdles, are not graded as class 3. (crown angle degree applies to rounds only)

3B grade:
A stone may be all 3B or 1A thru 4B. Any single characteristic of grade 4B must be within 2% or 1 degree of the 4A measurement. Only one class 4 characteristic permitted. Stones with class 4 extremely thick or extremely thin "overall" girdles are not graded as class 3. (crown angle degree applies to rounds only)

4A grade:
A stone may be all 4A or 1A thru 4B. Only two 4B characteristics are permitted at most. (crown angle degree rounds only)

4B grade:
Is all 4B or may be any combination from 1A thru 4B. Stones with more than two 4B characteristics are automatically 4B.

Round

  1A 1B 2A 2B 3A 3B 4A 4B
American Ideal Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %53.0%-58.0%52.0%-60.0%51.5%-63.0%51.0%-64.0%50.5%-67.0%50.0%-70.0%49.0%-72.0%<49.0%
>72.0%
Crown Angle34.0°-34.7°33.0°-35.1°32.1°-35.8°31.6°-36.4°30.1°-37.9°29.6°-39.4°29.0°-40.5°<29.0°
>40.5°
Crown Height %14.3%-16.3%13.5%-16.8%11.6%-17.9%11.1%-18.1%9.6%-19.3%8.5%-20.5%7.8%-21.8%<7.8%
>21.8%
Pavilion Depth %42.8%-43.2%42.5%-43.5%42.0%-44.0%41.5%-44.9%41.0%-45.5%40.5%-46.0%38.0%-48.0%<38.0%
>48.0%
Girdle ThicknessThin to Medium
Or
Medium to Slightly thick
Very thin to Medium
Or
Thin to Slightly thick
Very thin to Slightly thick Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %58.00%-62.30%58.30%-62.99%<58.30%
>62.99%
Polish / Symmetry1Excellent-Very GoodGood to ExcellentFair to GoodPoor

A diamond called a "Tolkowsky Cut" is only approximated by cut 1A. However, a "Tolkowsky Cut" is a very specifically calculated cut with the following parameters: Table 53.0%, Crown Angle 34.6, Crown Height 16.2%, Girdle Thickness app 1.7%, Pavilion Depth 43.1%. Many diamonds are improperly called "Tolkowsky Cut" when they are only approximating the parameters Tolkowsky formulated.

1Not a primary determining factor.

Princess

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %62.0%-68.0%60.0%-72.0%59.0%-74.0%58.0%-78.0%56.0%-82.0%53.0%-85.0%50.0%-88.0%<50.0%
>88.0%
Crown Height %10.0%-15.0%8.5%-16.0%8.0%-16.9%6.0%-18.0%5.0%-19.0%4.0%-19.9%3.0%-20.9%<3.0%
>21.0%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %64.0%-75.0%58.0%-80.0%57.0%-83.0%56.0%-84.0%53.0%-85.0%<53.0%
>85.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair


1Not a primary determining factor.

Emerald

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %60.0%-65.5%59.0%-68.0%58.0%-69.5%57.0%-72.0%56.0%-74.0%53.0%-76.0%50.0%-78.0%<50.0%
>78.0%
Crown Height %12.0%-15.0%11.0%-16.0%10.0%-16.5%9.0%-17.2%8.0%-18.0%7.0%-19.5%6.0%-20.5%<6.0%
>20.5%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %60.0%-65.0%58.0%-69.0%57.0%-74.0%56.0%-78.0%53.0%-80.0%<53.0%
>80.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair


1Not a primary determining factor.

Heart

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %55.0%-60.0%53.0%-61.5%52.0%-62.0%51.0%-64.0%51.0%-67.0%49.0%-70.0%48.0%-72.0%<48.0%
>72.0%
Crown Height %12.0%-15.0%11.5%-16.0%11.0%-16.6%10.1%-17.5%9.0%-18.0%8.3%-18.9%7.8%-19.5%<7.8%
>19.5%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %59.0%-63.0%58.0%-65.4%56.0%-68.5%46.0%-71.0%43.0%-73.0%<43.0%
>73.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair
Length: Width Ratios20.98-1.02


1Not a primary determining factor.
2Trade preferences. A matter of personal taste and choice.

Marquise

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %55.0%-60.0%53.0%-61.5%52.0%-62.0%51.0%-64.0%51.0%-67.0%49.0%-70.0%48.0%-72.0%<48.0%
>72.0%
Crown Height %12.0%-15.0%11.5%-16.0%11.0%-16.6%10.1%-17.5%9.0%-18.0%8.3%-18.9%7.8%-19.5%<7.8%
>19.5%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %59.0%-63.0%58.0%-65.4%56.0%-68.5%46.0%-71.0%43.0%-73.0%<43.0%
>73.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair
Length: Width Ratios21.75-2.25


1Not a primary determining factor.
2Trade preferences. A matter of personal taste and choice.

Pear

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %55.0%-60.0%53.0%-61.5%52.0%-62.0%51.0%-64.0%51.0%-67.0%49.0%-70.0%48.0%-72.0%<48.0%
>72.0%
Crown Height %12.0%-15.0%11.5%-16.0%11.0%-16.6%10.1%-17.5%9.0%-18.0%8.3%-18.9%7.8%-19.5%<7.8%
>19.5%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %59.0%-63.0%58.0%-65.4%56.0%-68.5%46.0%-71.0%43.0%-73.0%<43.0%
>73.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair
Length: Width Ratios21.50-1.75


1Not a primary determining factor.
2Trade preferences. A matter of personal taste and choice.

Oval

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %55.0%-60.0%53.0%-61.5%52.0%-62.0%51.0%-64.0%51.0%-67.0%49.0%-70.0%48.0%-72.0%<48.0%
>72.0%
Crown Height %12.0%-15.0%11.5%-16.0%11.0%-16.6%10.1%-17.5%9.0%-18.0%8.3%-18.9%7.8%-19.5%<7.8%
>19.5%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %59.0%-63.0%58.0%-65.4%56.0%-68.5%46.0%-71.0%43.0%-73.0%<43.0%
>73.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair
Length: Width Ratios21.33-1.66


1Not a primary determining factor.
2Trade preferences. A matter of personal taste and choice.

Radiant

  1A 1B 2A 2B 3A 3B 4A 4B
Ideal Cut Premium Cut International Fine Trade Cut US Domestic Average Cut Below Average
Table %60.0%-65.5%59.0%-68.0%58.0%-69.5%57.0%-72.0%56.0%-74.0%53.0%-76.0%50.0%-78.0%<50.0%
>78.0%
Crown Height %12.0%-15.0%11.0%-16.0%10.0%-16.5%9.0%-17.2%8.0%-18.0%7.0%-19.5%6.0%-20.5%<6.0%
>20.5%
Girdle ThicknessVery thin to Slightly thick
Or
Thin to Thick
Very thin to Thick Very thin to Very thick Extremely thin to Extremely thick
Total Depth %60.0%-65.0%58.0%-69.0%57.0%-74.0%56.0%-78.0%53.0%-80.0%<53.0%
>80.0%
Polish / Symmetry1Good to ExcellentFair to GoodPoor to Fair


1Not a primary determining factor.

 

There are diamonds that do not conform to the classic shape cut parameters and must be considered on an individual basis. ONE CANNOT GRADE UNUSUAL CUT DIAMONDS SOLELY ON ARBITRARY PARAMETERS. EXPERIENCE IN EXAMINING DIAMONDS FOR EFFECTIVE AND PRECISE CUTTING IS REQUIRED FOR CUTS NOT COVERED IN THESE CHARTS OF TYPICAL STANDARD CUT DIAMONDS.

The importance of visually examining the stone cannot be overstated -- let the numbers guide you when screening different stones. But in the final selection of the diamond for you, your eyes should always have the final say.

The final topic relating to "cut" is the quality of the workmanship involved in cutting a diamond. Continue with the tutorial to find out more.