Gemstone Weight Calculator

Work out gemstone weight instantly with clear inputs, formula shown and shareable results.

About Gemstone Weight Calculator

The trade estimate multiplies length by width by depth by specific gravity by a shape factor, which is about 0.0061 for a standard oval or round brilliant. Shape factor matters because the same bounding box holds very different amounts of material in an emerald cut versus a brilliant, so the factor changes by cut.

Formula

Weight estimate

carats = length x width x depth x specific gravity x shape factor

Worked example

With the default values below, Gemstone Weight Calculator returns Estimated weight of 4.1226. Change any input above and every figure here is recalculated in your browser.

Inputs used

Lengthminimum 0.01 mm: 8 mm
Widthminimum 0.01 mm: 6 mm
Depthminimum 0.01 mm: 4 mm
Specific gravityminimum 0.1: 3.52

Results

Estimated weight: 4.1226 ct
Weight in grams: 0.82452 g
Weight in points: 412.26
Stone volume: 234.240 mm3

Step by step

1Values used
2Weight estimate
3Estimated weight= 4.1226 ct
4Weight in grams= 0.82452 g
5Weight in points= 412.26
6Stone volume= 234.240 mm3

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Gemstone Weight figure worked out?

carats = length x width x depth x specific gravity x shape factor. The trade estimate multiplies length by width by depth by specific gravity by a shape factor, which is about 0.0061 for a standard oval or round brilliant.

Why does this matter?

Shape factor matters because the same bounding box holds very different amounts of material in an emerald cut versus a brilliant, so the factor changes by cut.

What do I need to enter?

Enter length, width, depth, specific gravity. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.