Diamond Carat to mm Calculator
Convert diamond carat weight to approximate millimeter diameter for round brilliant cut diamonds.
Approximate Diameter
6.50 mm
Approximate Diameter vs Diamond Weight
Formule
## Diamond Carat to Millimeter Conversion Diamond size (diameter) relates to carat weight through the cube root, since volume increases with the cube of the diameter. ### Formula (Round Brilliant) **Diameter (mm) = 6.5 x Carat^(1/3)** One carat equals 200 milligrams (0.2 grams). A 1-carat round diamond is approximately 6.5 mm in diameter. Doubling the carat weight only increases diameter by about 26% (cube root of 2).
Exemple Résolu
A 1.0 carat round brilliant diamond.
- 01Diameter = 6.5 x 1.0^(1/3) = 6.5 x 1.0 = 6.5 mm
- 02Weight = 1.0 x 200 = 200 mg
- 03Weight = 1.0 x 0.2 = 0.2 grams
Questions Fréquentes
Why does a 2-carat diamond not look twice as big?
Because diameter increases with the cube root of weight. A 2-carat round diamond is about 8.2 mm vs 6.5 mm for 1 carat, only 26% wider but covers about 59% more face-up area.
Does this work for all diamond shapes?
This formula is for round brilliant cuts. Fancy shapes (oval, pear, princess) have different proportions and may appear larger or smaller than a round of the same weight.
What is the most popular diamond size?
For engagement rings, 1.0-1.5 carats is most popular in the US. The most popular size worldwide is 0.5-0.7 carats.
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