DIAMOND EDUCATION

MM to Carat Conversion

Understanding mm to carat and how diamond size in millimeters relates to carat weight is essential when choosing a diamond. Because shape and cut affect how a diamond appears, using an accurate mm to carat conversion chart helps you confidently compare sizes and weights for any diamond.

Millimeter measurements describe a diamond’s physical size, while carat describes its weight. Because proportions differ by shape, the same carat weight looks different across cuts. Use the charts below to convert mm to approximate carat weight for each diamond shape.

ROUND CUT

MM Size	Carat Weight
0.8 mm.	0.0025 ct.
1 mm.	0.005 ct.
1.15 mm.	0.0067 ct.
1.12 mm.	0.0075 ct.
1.25 mm.	0.01 ct.
1.3 mm.	0.01 ct.
1.5 mm.	0.015 ct.
1.75 mm.	0.02 ct.
1.8 mm.	0.025 ct.
2 mm.	0.03 ct.
2.25 mm.	0.04 ct.
2.5 mm.	0.06 ct.
2.75 mm.	0.08 ct.
3 mm.	0.11 ct.
3.25 mm.	0.14 ct.
3.5 mm.	0.17 ct.
3.75 mm.	0.21 ct.
4 mm.	0.25 ct.
4.25 mm.	0.28 ct.
4.5 mm.	0.36 ct.
4.75 mm.	0.44 ct.
5.0 mm.	0.50 ct.
5.25 mm.	0.56 ct.
5.5 mm.	0.66 ct.
5.75 mm.	0.75 ct.
6 mm.	0.84 ct.
6.25 mm.	0.93 ct.
6.5 mm.	1.00 ct.
6.8 mm.	1.25 ct.

MM Size	Carat Weight
7 mm.	1.30 ct.
7.3 mm.	1.50 ct.
7.5 mm.	1.67 ct.
7.75 mm.	1.75 ct.
8 mm.	2.00 ct.
8.25 mm.	2.11 ct.
8.5 mm.	2.43 ct.
8.7 mm.	2.50 ct.
9 mm.	2.75 ct.
9.1 mm.	3.00 ct.
9.5 mm.	3.35 ct.
9.75 mm.	3.61 ct.
10 mm.	3.87 ct.
10.25 mm.	4.16 ct.
10.5 mm.	4.41 ct.
10.75 mm.	4.57 ct.
11 mm.	4.91 ct.
11.25 mm.	5.49 ct.
11.5 mm.	5.85 ct.
12 mm.	6.84 ct.
12.25 mm.	7.26 ct.
12.5 mm.	7.36 ct.
12.75 mm.	7.52 ct.
13 mm.	8.51 ct.
13.5 mm.	9.53 ct.
14 mm.	10.49 ct.
15 mm.	12.89 ct.
16 mm.	16.06 ct.

MM to Carat Conversion

Cushion cut

MM Size	Carat Weight
4.2 mm.	0.40 ct.
4.9 mm.	0.50 ct.
5.25 mm.	0.75 ct.
5.5 mm.	1.00 ct.
6 mm.	1.25 ct.
6.5 mm.	1.50 ct.
7 mm.	2.00 ct.
7.5 mm.	2.50 ct.

MM Size	Carat Weight
8 mm.	3.00 ct.
8.5 mm.	3.50 ct.
9 mm.	4.12 ct.
9.5 mm.	5.09 ct.
10 mm.	5.62 ct.
11 mm.	7.44 ct.
12 mm.	9.52 ct.
13 mm.	12.66 ct.

MM to Carat Conversion

Pear Shape

MM Size	Carat Weight
3×2 mm.	0.13 ct.
4×2.5 mm.	0.18 ct.
4×3 mm.	0.21 ct.
5×3 mm.	0.25 ct.
5×4 mm.	0.35 ct.
6×4 mm.	0.50 ct.
6.5×4.5 mm.	0.60 ct.
7×5 mm.	0.75 ct.
7.5×5.5 mm.	0.85 ct.
7.7×5.7 mm.	1.00 ct.
8×6 mm.	1.25 ct.
8.5×6.5 mm.	1.50 ct.
10×6 mm.	1.71 ct.
8.7×6.7 mm.	1.80 ct.
9×7 mm.	2.00 ct.
10×8 mm.	2.50 ct.
11×7.50 mm.	2.61 ct.
13×8 mm.	2.98 ct.
11×8 mm.	3.00 ct.

MM Size	Carat Weight
12×8 mm.	3.00 ct.
12×7 mm.	3.12 ct.
12×9 mm.	3.44 ct.
14×8 mm.	3.47 ct.
13×9 mm.	4.11 ct.
14×9 mm.	4.25 ct.
15×9 mm.	5.06 ct.
14×10 mm.	5.41 ct.
13×11 mm.	5.65 ct.
15×10 mm.	5.75 ct.
16×9 mm.	5.86 ct.
16×10 mm.	6.27 ct.
17×10 mm.	6.46 ct.
15×11 mm.	7.36 ct.
18×11 mm.	8.14 ct.
16×12 mm.	8.99 ct.
18×12 mm.	9.35 ct.
18×13 mm.	10.21 ct.

MM to Carat Conversion

Emerald cut

MM Size	Carat Weight
3×2 mm.	0.10 ct.
3.5×2 mm.	0.12 ct.
4×2 mm.	0.15 ct.
4×3 mm.	0.20 ct.
5×3 mm.	0.29 ct.
5.5×3.5 mm.	0.46 ct.
6×4 mm.	0.50 ct.
6.5×4.5 mm.	0.75 ct.
6.7×4.5 mm.	0.88 ct.
7×5 mm.	1.00 ct.
7.3×5.3 mm.	1.25 ct.
7.5×5.5 mm.	1.50 ct.
8×6 mm.	1.75 ct.
8.5×6.5 mm.	2.00 ct.

MM Size	Carat Weight
9×7 mm.	2.50 ct.
10×7.5 mm.	3.00 ct.
9.5×7.5 mm.	3.21 ct.
10×8 mm.	3.79 ct.
11×9 mm.	5.21 ct.
12×8 mm.	5.34 ct.
12×10 mm.	6.00 ct.
14×8 mm.	6.25 ct.
13×9 mm.	6.38 ct.
14×10 mm.	8.48 ct.
13×11 mm.	9.13 ct.
14×12 mm.	11.26 ct.
16×12 mm.	14.22 ct.

MM to Carat Conversion

Oval cut

MM Size	Carat Weight
4.5×3.5 mm.	0.21 ct.
5×3 mm.	0.21 ct.
5.5×3.5 mm.	0.33 ct.
5×4 mm.	0.35 ct.
6×4 mm.	0.50 ct.
6×5 mm.	0.61 ct.
6.5×4.5 mm.	0.65 ct.
7×5 mm.	0.75 ct.
7.7×5.7 mm.	1.00 ct.
8×6 mm.	1.25 ct.
9×6 mm.	1.41 ct.
8.5×6.5 mm.	1.50 ct.
9×7 mm.	2.00 ct.

MM Size	Carat Weight
10×8 mm.	2.50 ct.
10.5×8.5 mm.	2.88 ct.
12×8 mm.	3.00 ct.
11×9 mm.	3.85 ct.
12×10 mm.	5.05 ct.
14×10 mm.	5.81 ct.
13×11 mm.	6.05 ct.
14×12 mm.	8.21 ct.
15×12 mm.	8.76 ct.
16×12 mm.	9.32 ct.
16×14 mm.	11.88 ct.
18×13 mm.	12.86 ct.
20×15 mm.	14.96 ct.

MM to Carat Conversion

Princess cut

MM Size	Carat Weight
1.5 mm.	0.015 ct.
1.75 mm.	0.03 ct.
2 mm.	0.06 ct.
2.25 mm.	0.08 ct.
2.5 mm.	0.10 ct.
2.75 mm.	0.13 ct.
3 mm.	0.18 ct.
3.25 mm.	0.26 ct.
3.5 mm.	0.29 ct.
3.75 mm.	0.31 ct.
4 mm.	0.39 ct.
4.25 mm.	0.44 ct.
4.5 mm.	0.50 ct.
4.75 mm.	0.64 ct.
5 mm.	0.75 ct.
5.25 mm.	0.90 ct.
5.5 mm.	1.00 ct.
5.75 mm.	1.11 ct.
6 mm.	1.25 ct.
6.25 mm.	1.39 ct.

MM Size	Carat Weight
6.5 mm.	1.50 ct.
6.75 mm.	1.75 ct.
7 mm.	2.00 ct.
7.25 mm.	2.01 ct.
7.5 mm.	2.50 ct.
7.75 mm.	2.74 ct.
8 mm.	3.00 ct.
8.25 mm.	3.24 ct.
8.5 mm.	3.67 ct.
8.75 mm.	4.10 ct.
9 mm.	4.12 ct.
9.5 mm.	5.09 ct.
9.75 mm.	5.36 ct.
10 mm.	5.62 ct.
10.25 mm.	5.76 ct.
10.5 mm.	5.99 ct.
11 mm.	7.44 ct.
11.5 mm.	9.44 ct.
12 mm.	9.52 ct.

MM to Carat Conversion

Asscher cut

MM Size	Carat Weight
4 mm.	0.39 ct.
4.5 mm.	0.50 ct.
5 mm.	0.75 ct.
5.5 mm.	1.00 ct.
6 mm.	1.25 ct.
6.5 mm.	1.50 ct.
7 mm.	2.00 ct.
7.5 mm.	2.50 ct.

MM Size	Carat Weight
8 mm.	3.00 ct.
8.5 mm.	3.50 ct.
9 mm.	4.12 ct.
9.5 mm.	5.09 ct.
10 mm.	5.62 ct.
11 mm.	7.44 ct.
12 mm.	9.52 ct.
13 mm.	12.66 ct.

MM to Carat Conversion

Radiant cut

MM Size	Carat Weight
5×3 mm.	0.31 ct.
4.5×3.5 mm.	0.34 ct.
6×3 mm.	0.41 ct.
6×4 mm.	0.50 ct.
6.5×4.5 mm.	0.75 ct.
7×5 mm.	1.00 ct.
7.3×5.5 mm.	1.25 ct.
7.5×5.8 mm.	1.50 ct.
8×6 mm.	2.00 ct.
8.5×6.5 mm.	2.25 ct.
9×7 mm.	2.50 ct.
9.5×7.5 mm.	3.00 ct.
10×7 mm.	3.31 ct.

MM Size	Carat Weight
10×8 mm.	3.50 ct.
11×9 mm.	5.05 ct.
12×9 mm.	6.06 ct.
11.5×10 mm.	6.45 ct.
13×9 mm.	6.54 ct.
12×10 mm.	6.79 ct.
14×10 mm.	8.47 ct.
13×11 mm.	9.33 ct.
13.5×11.5 mm.	10.19 ct.
15×11 mm.	11.48 ct.
14×12 mm.	12.14 ct.
16×12 mm.	14.22 ct.

MM to Carat Conversion

Heart Cut

MM Size	Carat Weight
3.5 mm.	0.18 ct.
4 mm.	0.25 ct.
4.25 mm.	0.28 ct.
4.5 mm.	0.34 ct.
4.75 mm.	0.38 ct.
5 mm.	0.50 ct.
5.5 mm.	0.61 ct.
6 mm.	0.75 ct.
6.25 mm.	0.83 ct.
6.5 mm.	1.00 ct.
7 mm.	1.25 ct.
7.5 mm.	1.50 ct.

MM Size	Carat Weight
8 mm.	2.00 ct.
8.5 mm.	2.50 ct.
9 mm.	3.00 ct.
10 mm.	3.50 ct.
11 mm.	4.41 ct.
12 mm.	5.66 ct.
13 mm.	7.88 ct.
14 mm.	9.38 ct.
15 mm.	10.79 ct.
16 mm.	13.27 ct.
18 mm.	15.33 ct.

MM to Carat Conversion

Marquise cut

MM Size	Carat Weight
3×1.5 mm.	0.025 ct.
3.5×1.75 mm.	0.065 ct.
3.5×2 mm.	0.07 ct.
4×2 mm.	0.10 ct.
3.75×1.75 mm.	0.11 ct.
4.25×2.25 mm.	0.12 ct.
5×2.5 mm.	0.14 ct.
5.5×2.75 mm.	0.16 ct.
5.5×3 mm.	0.18 ct.
5×3 mm.	0.20 ct.
6.5×3 mm.	0.23 ct.
6×3 mm.	0.25 ct.
7×3 mm.	0.30 ct.
7.5×3.5 mm.	0.33 ct.
7×4 mm.	0.34 ct.
8×4 mm.	0.50 ct.
8.75×4.25 mm.	0.70 ct.
9×4.5 mm.	0.75 ct.

MM Size	Carat Weight
9.5×4.7 mm.	0.85 ct.
10×5 mm.	1.00 ct.
11×5.5 mm.	1.25 ct.
11.5×6 mm.	1.33 ct.
12×6 mm.	1.50 ct.
13×6.5 mm.	2.00 ct.
14×7 mm.	2.50 ct.
15×7 mm.	3.00 ct.
14×8 mm.	3.00 ct.
15×7.5 mm.	3.25 ct.
15×8 mm.	3.44 ct.
16×8 mm.	3.86 ct.
16.5×8.25 mm.	4.00 ct.
17×8.5 mm.	4.88 ct.
17.5×10 mm.	5.50 ct.
20×8 mm.	7.08 ct.
20×10 mm.	7.94 ct.
20×11 mm.	9.50 ct.

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MM to Carat Conversion

ROUND CUT

Cushion cut

Pear Shape

Emerald cut

Oval cut

Princess cut

Asscher cut

Radiant cut

Heart Cut

Marquise cut

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