Carat Weight Calculator

Your details

The mineral species determines the specific gravity. Diamond uses a different coefficient set because its SG is already baked into the published shape factors.
Each cut has a different shape factor reflecting how much of the bounding-box volume the finished stone actually occupies.
Longest face dimension in millimetres. For round stones use diameter here and also as the width.
mm
Shortest face dimension. For round stones this equals the diameter (same as length).
mm
Total depth from table to culet, measured with calipers. Typically 60-63 % of diameter for a well-cut round brilliant.
mm
Estimated carat weightHalf-carat range
0.9ct

Approximate carat weight from the industry formula

Weight in grams0.18g
Troy ounces0.0064ozt
Shape factor used0.0061
Specific gravity used3.52
Carats (ct)0.9
Grams (g)0.18

Estimated weight: 0.90 carats

  • The estimated weight is 0.90 ct (0.180 g).
  • Depth is 61.9 % of diameter, within the ideal 59-63 % range for a round brilliant.
  • Formula results are estimates only. Actual weight should be confirmed by placing the stone on a calibrated gem scale.

Next stepFor a precise weight, use a gemological scale accurate to 0.001 ct. For a diamond purchase, ask for the GIA grading report, which lists the exact certified weight.

 = Powered by OnlyCalculators