Gemstone Weight Calculator from Dendritics

Carat Weight Calculator. How to measure carats when a stone is mounted. Using our Proprietary Advanced Formula for Round, Emerald, Marquise, Radiant, and Oval cuts which takes into account the culet size, shape of the sides, roundness of the belly, variations in the girdle as well as table proportion.

New for 2019! Add up a series of carat weights, no need to write them down and use a calculator. 5 rubies in a ring or 100 diamonds in a necklace. If you make a mistake, uncheck it in the list and keep on going. Stone Identification. is now separate.


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Measure (mm)

Length Width



Girdle ...

 Select Stone
(Common stones first)

 Enter Weight


(Your Answer Will be here)

 Accumulated Weight

0.00 Ct


0 Using the proprietary Dendritics Advanced Formula.
1 Using the relatively crude Standard Formula, with larger indicated uncertainty than on other cuts. You need only enter the basic Measurements and Belly Shape.
2 Square cushion. Enter corner & belly measurements as Length and Width. Also uses the Standard Formula. You need only enter the basic Measurements and Belly Shape.
3 Pear and Heart cuts. These are the only cuts to use Side Shape (curvature).
4 Cabochon, Spheroid and Octahedron. You need only enter the basic Measurements.
5 We hope you enjoy the updated, cleaner interface. The original version is here. Your suggestions are welcomed ()

Images and webpage designs by jb, © 2023 Dendritics Inc.