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Size & Fit
See how a stone sits on finger next to a dime or on a millimetre ruler — available on every gem product page.
Browse gems with Size & Fit →Seylan Gems & Jewelry
Convert millimetre measurements into an estimated carat weight, then browse matching stones or talk with a specialist.
Carat calculator
Enter face-up length and width depth if known gem type and cut shape. Results update as you type.
Depth is the pavilion measurement — leave blank to estimate later
Formula:
ct ≈ L × W × D × SG × shapeFactor ÷ 1000
Estimate only — cut style girdle thickness and treatment can change actual weight. Not a lab certificate or insurance appraisal.
Buying tools
Use these tools alongside our catalog — then confirm with a specialist before you buy or insure.
Shop by gem
Jump into popular categories after you estimate carat weight.
Formal appraisal
For insurance estate or certification needs we can help you choose reputable labs and walk through documentation. Online estimates here are educational only.
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