mm to Carat Conversion

This diamond weight estimator converts millimetre dimensions, cut shape, girdle, and correction factors into an approximate carat weight.

Formula notes

carats = shape factor x depth x length x width x (1 + girdle) x (1 + correction); round diamonds use diameter squared with the captured round factor.

Worked examples

1. Example: a 6.5 mm round diamond with 4 mm depth and no adjustments estimates about 1.03 carats.
2. A 6 x 4 x 3 mm princess diamond estimates about 0.60 ct with the captured princess factor.

How to use it

1. Choose the diamond shape.
2. Enter length, width or diameter, and depth in mm.
3. Add girdle and weight corrections if you know them, then read estimated carats and grams.

Frequently asked questions

Limits and interpretation

• The estimate is a reference from a captured shape-factor table, not a certified grading result.
• Measurements are sensitive to caliper technique and cut proportions; small differences change the estimate.