This is a guide on how to estimate the approximate weight of a gemstone based on its length to width ratio.
Round
Diamond: Average diameter² x depth x 0.0061 x weight correction٭
Color Stone: Average diameter² x depth x S.G. x 0.0018 x weight correction*
Oval
Diamond: Average diameter² x depth x 0.0062 x weight correction٭
Colored Stone: Average diameter² x depth x S.G. x 0.0020 x weight correction*
(use average length and width for diameter)
Pear
Diamond: Length x width x depth x adjustment factor x weight correction٭
Adjustment Factor
Length to width Ratio |
Adjustment Factor |
1.25:1.00 | 0.00615 |
1.50:1.00 |
0.00600 |
1.66:1.00 |
0.00590 |
2.00:1.00 |
1.00575 |
Colored Stone: Length x width x depth x S.G. x 0.0018 x weight correction*
Marquise
Diamond: Length x width x depth x adjustment factor x weight correction٭
Adjustment Factor
Length to width Ratio |
Adjustment Factor |
1.25:1.00 | 0.00565 |
2.00:1.00 |
0.00580 |
2.50:1.00 |
0.00585 |
3.00:1.00 |
1.00595 |
Emerald Cut
Diamond: Length x width x depth x adjustment factor x weight correction*
Adjustment Factor
Length to width Ratio |
Adjustment Factor |
1.00:1.00 | 0.0080 |
1.50:1.00 |
0.0092 |
2.00:1.00 |
0.0100 |
2.50:1.00 |
0.0106 |
Heart
Diamond: Length x width x depth x 0.0059 x weight correction٭
Colored Stone: Length x width x depth x S.G. x 0.0021 x weight correction*
Triangle
Diamond: Length x width x depth x 0.0057 x weight correction٭
Colored Stone: Length x width x depth x S.G. x 0.0018 x weight correction*
٭ Weight Correction
All Cuts: Add between 3% and 8% depending on thickness of the girdle. A high or lumpy crown may require a correction of up to 10%.
Oval, Pear, Marquise, Heart: Add up to 10% for wide wings or high shoulders.
Step Cuts: Add up to 18% for pavilion bulge.
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