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.
In more detail
A thick girdle and a deep stone add weight that doesn't show face up. In our simulator, a Poor-cut 1.00 ct T73 is only 6.16 mm across. That is the width of an Excellent T73 of about 0.86 ct. GIA uses the total depth to help judge weight ratio, and its Excellent limit is 63%.
On a grading report
Not printed as its own line: read it from the total depth and girdle on the proportion diagram.
Related terms
- Cut grade: The cut grade rates how well a diamond's proportions and finish work, from Excellent to Poor. GIA gives it only to standard round brilliants in the D-to-Z color range.
- Total depth: 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.
- 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".
- Durability (cut grade): Durability is the part of GIA's cut grade that checks for a risk of damage. The risk comes from a very thin girdle or thin points.