Gemstone Weight Estimation Calculator (+ Formulas)
I have created a free and hopefully easy-to-use weight estimation calculator for coloured gemstones.
Simply select the stone type and shape and then enter the length, width and depth and the tool will automatically estimate the weight of the stone (+ the l/w ratio for all shapes except round.
You can also adjust for any pavilion bulge by using the drop-down menu.
If you need to do this for a Diamond, then you need my Diamond weight calculator.
I do have to stress that this is an estimator and there is likely to be a difference between the estimated weight and the actual weight of the stone but to make the tool as useful as possible, I have the tool set up to show estimated weight ranges for stones that have an SG range, such as:
- Emerald: 2.67 – 2.78
- Spinel: 3.54 – 3.63
All of the SG figures used in the tool are from Gemstones of the World by Walter Schumann (I recommend anyone interested in gemstones or gemmology get yourself a copy, as it is so useful).
Weight Estimation Formulas
If you are interested in the science behind the tool, I have included all the formulas I have used in the table below:
| Stone Shape | Formula |
|---|---|
| Round (faceted) | Weight = (average diameter)2 x Depth x SG x 0.0018 |
| Oval (faceted) | Weight = (L x W / 2)2 x Depth x SG x 0.0020 |
| Marquise (faceted) | Weight = L x W x D x SG x 0.0019 |
| Pear (faceted) | Weight = L x W x D x SG x 0.0020 |
| Heart (faceted) | Weight = L x W x D x SG x 0.0019 |
| Step (faceted) | Weight = L x W x D x SG x 0.0030 |
| Emerald (faceted) | Weight = L x W x D x SG x 0.0027 |
| Oval Cabochon | Weight = L x W x D x SG x 0.0026 |