At Blue Nile, we define diamond cut based on table percentage and depth percentage. Below, learn how to determine table and depth percentage of a particular diamond.


Table Percentage

The table percentage is the diameter of the top facet (or table) compared to the diamond's width. For a diamond with the most sparkle and fire, we recommend a diamond in which the table measures between 51% and 65% of the total diamond width. These measurements are stated on the diamond certificate.

Example:     If the table equals 5mm, and the width equals 9mm, 5 divided by 9 = 55%, which qualifies as ideal table percentage.

For More Information

Fancy Diamond Shapes


 

Read how fancy diamond cuts, like emerald and oval, are graded differently than round diamonds.

Diamond Anatomy Diagram


Learn the parts that make up a diamond. View our diamond anatomy diagram.


Depth Percentage

The depth percentage is the height of the diamond (measured from the tip of the culet to the table) compared to the diameter of the diamond (the top of the diamond measured through the middle from one edge of the girdle to the other). To avoid buying a diamond that loses light out the bottom, look for a diamond in which the height measures between 57.5% and 64.5% of the total diamond width. You'll find this measurement on the diamond certificate.

Example:     If the height equals 5mm, and the width equals 8mm, 5 divided by 8 = 62.5%, which qualifies as ideal depth percentage.

You'll notice the depth and table percentages are already calculated in an AGSL grading report, but the GIA grading report lists the depth, diameter and table measurements. You'll notice when you perform a diamond search, that we've calculated the depth and table percentages for you and display them for each diamond so that you can easily compare GIA and AGSL graded diamonds.

For each grade of diamond cut, the chart below lists the depth percentage and table percentage for each Blue Nile cut grade.

Blue Nile Round Diamond Grade Proportion

 

Signature Ideal

Ideal

Very Good

Good

Not Suggested

Depth

60.1-61.9%

60.1-62.8%

58.5-64%

57.5-64.5%

<57.5->64.5%

Table

55-57%

53-57%

52-60%

51-65%

<51->65%

Symmetry and Polish

Two other grades that can help you make a decision between diamonds with similar depth percentage and table percentage are symmetry and polish. Symmetry refers to the balance and alignment of the facets. If a diamond appears unbalanced and alignment of the facets is not consistent, it will have poor symmetry. Polish refers to the diamond cutter's finishing details. Each facet of a diamond must be polished with finer and finer grades of diamond dust to make each edge crisp and each facet smooth and clear. The diamond polisher must be careful not to leave any polishing marks on the facets.

Symmetry and polish are graded by the AGSL as ideal, excellent, very good, good, fair, and poor, and by the GIA as excellent, very good, good, fair, or poor. For the most beautiful, clear sparkle, look for a diamond with excellent-to-good symmetry and polish grades.