Gemstone Weight Calculator

This free gemstone weight calculator helps you estimate the carat weight of sapphires, emeralds, rubies, and more. Jewellers, collectors, and gem enthusiasts worldwide use this tool to quickly approximate gemstone weight.

Gemstone Weight Calculator by Desiree Gems

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Brilliant cuts use a different constant than step cuts. For very thick girdles or unusually deep stones, add +10–20% in Weight Correction.

Formulae used:
• Brilliant family (round/oval/pear/marquise/most cushions): ct ≈ L × W × D × K, where K ≈ 0.0061 for diamond and scales by SG/3.52 for other gems.
• Step family (emerald/princess/asscher/radiant): ct ≈ L × W × D × (0.00270 × SG), then apply optional Weight Correction (%).

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