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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 SizeCarat WeightRound MM SizeCarat Weight
0.80.002571.3
10.0057.251.49
1.120.00757.51.67
1.150.00677.751.75
1.250.0182.04
1.30.018.252.10
1.50.0158.752.43
1.750.0292.75
1.800.0259.253.05
20.039.53.35
2.250.049.753.6
2.50.06103.87
2.750.0810.254.15
30.1010.54.4
3.250.1410.754.57
3.50.17114.9
3.750.2111.255.49
40.2511.55.85
4.250.28126.84
4.50.3612.257.25
4.750.4412.57.36
50.4612.757.5
5.250.56138.5
5.50.6613.59.5
5.750.761410.5
60.841512.9
6.250.931616.06
6.41.001718.00
6.751.25
Princess MM SizeCarat WeightPrincess MM SizeCarat Weight
1.50.0156.51.59
1.750.036.751.75
20.0671.96
2.250.017.52.4
2.50.17.752.74
2.750.137.752.74
30.1883.01
3.250.268.253.24
3.50.298.53.67
3.750.318.754.1
40.3994.12
4.250.449.55.09
4.50.559.755.36
4.750.64105.62
50.7110.255.76
5.250.7510.55.99
5.50.99117.44
5.751.1111.59.44
61.24129.52
6.251.39
Cushion MM SizeCarat WeightCushion MM SizeCarat Weight
40.2582.04
4.50.368.52.43
50.4692.75
5.250.569.53.35
5.50.66103.87
5.750.7610.54.41
60.84114.91
6.250.9311.55.85
6.51.03126.84
6.751.24138.51
71.281410.49
7.51.671512.89
Emerald MM SizeCarat WeightEmerald MM SizeCarat Weight
3 x 20.19 x 7
2.62
3.5 x 2
0.129.5 x 7.5
3.20
4 x 2
0.1510 x 7
3.02
4 x 3
0.210 x 8
3.79
5 x 3
0.2911 x 9
5.21
5.5 x 3.5
0.4612 x 8
5.34
5.5 x 4
0.4812 x 10
6
6 x 4
0.6613 x 9
6.38
6.5 x 4.5
0.8814 x 8
6.25
7 x 5
1.0614 x 10
8.48
7.25 x 5.25
1.2413 x 11
9.13
7.5 x 5.5
1.4514 x 12
11.26
8 x 6
1.7416 x 12
14.22
8.5 x 6.5
2.17
Pear MM SizeCarat WeightPear MM SizeCarat Weight
3 x 20.13
12 x 8
3
4 x 2.5
0.1812 x 9
3.44
4 x 3
0.21
13 x 8
2.99
5 x 3
0.2514 x 8
3.47
5 x 4
0.3513 x 9
4.11
6 x 4
0.3914 x 9
4.25
6.5 x 4.5
0.5715 x 9
5.06
7 x 5
0.7114 x 10
5.41
8 x 5
0.8113 x 11
5.65
8.5 x 5.5
1.08
15 x 10
5.75
8 x 6
1.2515 x 11
7.36
9 x 6
1.33
16 x 9
5.86
9 x 7
1.7516 x 10
6.27
10 x 6
1.7116 x 12
8.99
10 x 7
1.817 x 10
6.46
10 x 8
2.4618 x 11
8.14
11 x 7.50
2.6118 x 12
9.35
11 x 8
318 x 13
10.21
12 x 7
3.12
Oval MM SizeCarat Weight
1.50.015
1.750.03
20.06
Radiant MM SizeCarat Weight
1.50.015
1.750.03
20.06
Assher MM SizeCarat Weight
1.50.015
1.750.03
20.06
Marquise MM SizeCarat Weight
1.50.015
1.750.03
20.06