Total depth is the height of a stone from table to culet as a percentage of its average diameter. It equals crown height + girdle thickness + pavilion depth.
In more detail
To check it, divide the depth in the measurements by the average diameter. GIA's Excellent range is 57.5 to 63%, and over 63% usually means extra weight below the face. For a fancy shape, depth is a percentage of the width.
On a grading report
On the proportion diagram as "total depth". IGI's Ideal band is 58.5 to 62.5%.
Related terms
- Measurements: Measurements is the report line that gives a stone's size in millimeters. A round reads minimum – maximum diameter × depth, and a fancy shape length × width × depth.
- Crown height: Crown height is the height of the crown, from the girdle to the table. It is a percentage of the average diameter.
- Pavilion depth: Pavilion depth is the depth of the pavilion, from the girdle to the culet. It is a percentage of the average diameter.
- Girdle thickness: Girdle thickness is how thick the girdle is at its thinnest and thickest points. A report gives it as a range of words, such as "Thin to Medium".
- Weight ratio: Weight ratio is the part of GIA's cut grade that compares a diamond's weight with its diameter. A stone can carry too much or too little weight for its width.