JewelLoop · Gem carat weight estimator
https://jewelloop.net/tools/gem-carat-weight-estimator/
Estimates for guidance; verify before production.
Gem carat weight estimator
Estimate the carat weight of a diamond or coloured gemstone from its measurements, for example when the stone is already set.
Estimated weight
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- Grams
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- Length to width
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Factor used: –
Set up actual size for this screen
Hold any bank or ID card (they are all 85.60 × 53.98 mm) against the screen and move the slider until the dashed outline matches its edges. Remembered on this device only.
Estimates for guidance; verify before production.
Understand the result
How the estimate works
The calculator uses the standard trade formulas: length × width × depth × a factor for the shape. For coloured stones the result is multiplied by the stone's specific gravity, because a ruby (4.00) weighs much more than an emerald (2.72) of the same size.
The shape factors come from the weight estimation formulas published in Palmieri's Market Monitor (GCAL), based on GIA and AGS practice. Real stones vary with their proportions, so expect a difference of a few percent.