MM to carat weight conversion

Millimeter (mm) measurements reflect the gemstone’s dimensions, while carats measure weight, and understanding those differences is important in jewelry shopping. Carat weight affects a diamond’s appearance, it doesn’t directly equate to size, as two diamonds of the same weight can look different depending on how the weight is distributed. The charts below provide estimated diamond millimeter-to-carat conversions, which may vary for other gemstones due to differences in density.

Calculate Weight

Select MM Size:

Estimated Carat Weight

0.01 ct

ROUND Reference Chart

MM Size	Carat Weight
1.3 mm	0.01 ct
5.0 mm	0.50 ct
1.6 mm	0.02 ct
5.6 mm	0.65 ct
2.0 mm	0.03 ct
5.9 mm	0.75 ct
2.2 mm	0.04 ct
6.5 mm	1.00 ct
2.3 mm	0.05 ct
7.0 mm	1.25 ct
2.5 mm	0.06 ct
7.4 mm	1.50 ct
2.7 mm	0.07 ct
7.8 mm	1.75 ct
3.0 mm	0.10 ct
8.0 mm	2.00 ct
3.2 mm	0.12 ct
8.5 mm	2.25 ct
3.4 mm	0.15 ct
9.0 mm	2.50 ct
3.5 mm	0.18 ct
9.4 mm	3.00 ct
3.8 mm	0.20 ct
10.0 mm	3.50 ct
4.0 mm	0.25 ct
10.5 mm	4.00 ct
4.5 mm	0.35 ct
11.0 mm	4.50 ct
4.8 mm	0.40 ct
12.0 mm	5.00 ct

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