Diamond Weight Calculator

This is an old mine cut diamond weight calculator or diamond weight estimator that utilizes industry-accepted diamond weight calculator formulas based on the cut of the diamond (e.g. old mine cut).

*Girdle Correction (%)

GIA Laboratory describes girdle thickness as representing “the thinnest and thickest “valley” positions on the girdle of the round brilliant (i.e., thin areas located where the upper and lower half facets meet) relative to the average diameter of the diamond.”

To calculate girdle correction, divide the girdle thickness (in millimeters) by the average diameter (in millimeters) and multiply by 100:

Weight Adjustment

Weight adjustment is used to account for the different diamond shapes. The weight adjustment relies on the length to width ratio of the diamond and diamond shape. Here are tables that contains the weight adjustment for specific diamond shapes:

Emerald Weight Correction Table

Length to Width Ratio	Adjustment Factor
1:1	0.0080
1.5:1	0.0092
2:1	0.01
2.5:1	0.0106

Radiant Weight Correction Table

Length to Width Ratio	Adjustment Factor
1:1	0.0081
1.5:1	0.0084

Marquise Weight Correction Table

Length to Width Ratio	Adjustment Factor
1.5:1	0.00565
2:1	0.0058
2.5:1	0.00585
3:1	0.00595

Pear Weight Correction Table

Length to Width Ratio	Adjustment Factor
1.25:1	0.00615
1.5:1	0.006
1.66:1	0.0059
2:1	0.00575