Reference

Diamond Size Guide

Approximate carat weight by millimeter measurement, by shape. These are industry-standard approximations, not lab measurements. Actual weight depends on cut depth and proportions, not just diameter.

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Round

mmApprox. ct
3.00.10
3.50.15
4.00.25
4.50.35
5.00.50
5.50.61
6.00.75
6.50.88
7.01.13
7.51.50
8.01.75
9.02.50
10.03.20

Princess

mmApprox. ct
4.00.30
4.50.40
5.00.60
5.50.75
6.01.00
6.51.30
7.01.50

Cushion

mmApprox. ct
5.00.50
5.50.70
6.01.00
6.51.25
7.01.50
7.52.00

Oval (L × W)

mmApprox. ct
6×40.50
7×50.75
8×61.20
9×72.00
10×82.90

Emerald Cut (L × W)

mmApprox. ct
5×30.30
6×40.50
7×50.90
8×61.50
9×72.00

Pear (L × W)

mmApprox. ct
6×40.50
7×50.75
8×51.00
9×61.50
10×72.00

Marquise (L × W)

mmApprox. ct
6×30.25
8×40.50
10×51.00
12×61.50
14×72.00

Asscher

mmApprox. ct
4.00.30
4.50.40
5.00.60
5.50.80
6.01.00
6.51.30
7.01.60

Radiant (L × W)

mmApprox. ct
5×30.30
6×40.50
7×50.90
8×61.50
9×72.10

Heart

mmApprox. ct
5.00.40
5.50.50
6.00.75
6.51.00
7.01.25
7.51.50
8.02.00

Baguette (L × W)

mmApprox. ct
3.0×2.00.10
3.5×2.20.14
4.0×2.20.17
4.5×2.50.23
5.0×2.50.28
5.5×2.70.34
6.0×3.00.42

Trapezoid (L × W)

mmApprox. ct
5×40.35
6×50.55
7×50.70
8×61.00

Trilliant

mmApprox. ct
5.00.35
6.00.60
7.00.90
8.01.30
9.01.80

These are industry-standard approximations, not lab measurements. Two stones of the same diameter can differ in weight based on how deep they're cut. When it matters, ask for the certified weight.