Diamond Carat Weight Calculator
Estimate the carat weight of a diamond based on its shape and millimeter dimensions. Supports Round, Princess, Emerald, Marquise, and other popular cuts.
About
When a diamond is mounted in a ring or setting, it is often impossible to weigh it directly without removing it, which risks damaging the piece. Professional gemologists use precise volumetric formulas to estimate the carat weight based on physical dimensions like diameter, depth, and length. This estimation is critical for insurance appraisals, valuation, and identifying potential discrepancies in sold stones.
This tool utilizes standard gemological formulas that factor in the specific gravity of diamond (approximately 3.52) and the unique geometric profile of various cuts. Keep in mind that girdle thickness and variations in cut proportions (thick vs. thin) can cause slight deviations from the calculated weight.
Formulas
The general logic calculates the volume of the stone and multiplies it by the specific gravity of diamond and a shape-specific correction factor.
Round Brilliant Formula:
Fancy Cuts (General) Formula:
Where d is diameter, h is depth, L is length, and W is width (all in mm).
Reference Data
| Diamond Cut | L/W Ratio (Ideal) | Weight Correction Factor | Calculation Basis |
|---|---|---|---|
| Round Brilliant | 1.00 | 0.0061 | Diameter² × Depth |
| Oval | 1.30 - 1.50 | 0.0062 | Length × Width × Depth |
| Princess (Square) | 1.00 - 1.05 | 0.0083 | Length × Width × Depth |
| Emerald | 1.30 - 1.50 | 0.0080 | Length × Width × Depth |
| Marquise | 1.85 - 2.10 | 0.00565 | Length × Width × Depth |
| Pear (Teardrop) | 1.50 - 1.70 | 0.00615 | Length × Width × Depth |
| Heart | 0.90 - 1.10 | 0.0059 | Length × Width × Depth |
| Cushion | 1.00 - 1.20 | 0.00815 | Length × Width × Depth |
| Radiant | 1.00 - 1.40 | 0.0081 | Length × Width × Depth |
| Asscher | 1.00 | 0.0080 | Length × Width × Depth |