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٭
Colored 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٭
Colored Stone: Length x width x depth x S.G. x 0.0018 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

 

 

Baguette

Diamond: length x width x depth x 0.00915

 

 

Tapered Baguette

Diamond: length x width x depth x 0.00915
(Width = the average of the two parallel edges)

 

 

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

 

 

Square, Princess or Rectangular Cut

Diamond: length x width x depth x 0.0083 x weight correction*

 

 

Emerald or Radiant 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.