Best Gemstones | Luxury Gemstones

Estimating Weight of Diamonds

Because of the variations in browser settings, screen resolutions and monitor variations; accurately showing sizes on a screen is impossible.

Find a template with calibrated holes then you can make the following estimates. If you want to use circle sizes where the diameter is printed, make sure you know whether the measurement is the outside or inside of the circle.

When you have determined the diameter and depth, use our free gem weight calculator, which works well for all shapes and many different gemstones.

Diameter – mm Weight – carat
2.2 0.04
3.0 0.10
4.1 0.25
5.2 0.50
6.5 1.00
7.4 1.50
8.2 2.00
9.0 2.50
9.3 3.00
11.0 5.00



For other diameters use the following formulas

  • Weight in carats = diameter² x depth x 0.0061
  • If you cannot measure the depth but the diamond is well proportioned — Weight in carats = diameter³ x 0.0037
  • All measurements assumed to be in millimeters

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