SDE.NO Diamond MM to CT Conversion Charts

Our conversion charts will help you determine what might be the right carat weight by providing a mm to carat comparison. The diamond size chart is meant to be a reference point, as diameters of diamonds vary based on cut quality.

In the diamond size charts below, we display the diamond’s diameter mm to carat weight based on averages of the most common shapes. For example, a round diamond’s diameter of 6.40mm to carat is 1.00ct. on average, but can easily weigh +/- 10% depending on the cut grade.

Diamonds are measured in both carat weight and millimeter, but are purchased and sold based on their weight. Carat weight is the standard unit of measurement for loose diamonds — and 1.00ct is equal to 0.2gram. It is important to consider millimeter measurements and ratios to choose the best possible option for your budget.

A diamond's millimeter measurement tells you its true size. That's because a diamond of the same carat weight can have slightly different faceting and therefore look larger than a carat weight equivalent. If you're looking for a diamond that looks larger faceup, consider getting a fancy shape diamond: Shapes like emerald, oval, and pear often look larger than their round counterparts.

Round MM Size	Carat Weight	Round MM Size	Carat Weight
0.8	0.0025	7	1.3
1	0.005	7.25	1.49
1.12	0.0075	7.5	1.67
1.15	0.0067	7.75	1.75
1.25	0.01	8	2.04
1.3	0.01	8.25	2.10
1.5	0.015	8.75	2.43
1.75	0.02	9	2.75
1.80	0.025	9.25	3.05
2	0.03	9.5	3.35
2.25	0.04	9.75	3.6
2.5	0.06	10	3.87
2.75	0.08	10.25	4.15
3	0.10	10.5	4.4
3.25	0.14	10.75	4.57
3.5	0.17	11	4.9
3.75	0.21	11.25	5.49
4	0.25	11.5	5.85
4.25	0.28	12	6.84
4.5	0.36	12.25	7.25
4.75	0.44	12.5	7.36
5	0.46	12.75	7.5
5.25	0.56	13	8.5
5.5	0.66	13.5	9.5
5.75	0.76	14	10.5
6	0.84	15	12.9
6.25	0.93	16	16.06
6.4	1.00	17	18.00
6.75	1.25

Princess MM Size	Carat Weight	Princess MM Size	Carat Weight
1.5	0.015	6.5	1.59
1.75	0.03	6.75	1.75
2	0.06	7	1.96
2.25	0.01	7.5	2.4
2.5	0.1	7.75	2.74
2.75	0.13	7.75	2.74
3	0.18	8	3.01
3.25	0.26	8.25	3.24
3.5	0.29	8.5	3.67
3.75	0.31	8.75	4.1
4	0.39	9	4.12
4.25	0.44	9.5	5.09
4.5	0.55	9.75	5.36
4.75	0.64	10	5.62
5	0.71	10.25	5.76
5.25	0.75	10.5	5.99
5.5	0.99	11	7.44
5.75	1.11	11.5	9.44
6	1.24	12	9.52
6.25	1.39

Cushion MM Size	Carat Weight	Cushion MM Size	Carat Weight
4	0.25	8	2.04
4.5	0.36	8.5	2.43
5	0.46	9	2.75
5.25	0.56	9.5	3.35
5.5	0.66	10	3.87
5.75	0.76	10.5	4.41
6	0.84	11	4.91
6.25	0.93	11.5	5.85
6.5	1.03	12	6.84
6.75	1.24	13	8.51
7	1.28	14	10.49
7.5	1.67	15	12.89

Emerald MM Size	Carat Weight	Emerald MM Size	Carat Weight
3 x 2	0.1	9 x 7	2.62
3.5 x 2	0.12	9.5 x 7.5	3.20
4 x 2	0.15	10 x 7	3.02
4 x 3	0.2	10 x 8	3.79
5 x 3	0.29	11 x 9	5.21
5.5 x 3.5	0.46	12 x 8	5.34
5.5 x 4	0.48	12 x 10	6
6 x 4	0.66	13 x 9	6.38
6.5 x 4.5	0.88	14 x 8	6.25
7 x 5	1.06	14 x 10	8.48
7.25 x 5.25	1.24	13 x 11	9.13
7.5 x 5.5	1.45	14 x 12	11.26
8 x 6	1.74	16 x 12	14.22
8.5 x 6.5	2.17

Pear MM Size	Carat Weight	Pear MM Size	Carat Weight
3 x 2	0.13	12 x 8	3
4 x 2.5	0.18	12 x 9	3.44
4 x 3	0.21	13 x 8	2.99
5 x 3	0.25	14 x 8	3.47
5 x 4	0.35	13 x 9	4.11
6 x 4	0.39	14 x 9	4.25
6.5 x 4.5	0.57	15 x 9	5.06
7 x 5	0.71	14 x 10	5.41
8 x 5	0.81	13 x 11	5.65
8.5 x 5.5	1.08	15 x 10	5.75
8 x 6	1.25	15 x 11	7.36
9 x 6	1.33	16 x 9	5.86
9 x 7	1.75	16 x 10	6.27
10 x 6	1.71	16 x 12	8.99
10 x 7	1.8	17 x 10	6.46
10 x 8	2.46	18 x 11	8.14
11 x 7.50	2.61	18 x 12	9.35
11 x 8	3	18 x 13	10.21
12 x 7	3.12

Oval MM Size	Carat Weight
1.5	0.015
1.75	0.03
2	0.06

Radiant MM Size	Carat Weight
1.5	0.015
1.75	0.03
2	0.06

Assher MM Size	Carat Weight
1.5	0.015
1.75	0.03
2	0.06

Marquise MM Size	Carat Weight
1.5	0.015
1.75	0.03
2	0.06