Lab grown diamond size chart: carat to mm
By HeyGema™ · Updated
In short
A lab grown diamond is the same material as a mined one, with the same density (3.52), so its size in mm for a given carat weight is the same: 6.5 mm round at 1 carat, 8.1 mm at 2 carat.
Carat to mm calculator
About 6.5 x 6.5 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
Lab grown diamond size by carat and shape
Length x width of a well-cut lab grown diamond. The numbers are the same for mined diamonds.
| Shape | 0.5 ct | 1 ct | 1.5 ct | 2 ct | 3 ct | 4 ct | 5 ct |
|---|---|---|---|---|---|---|---|
| Round | 5.1 | 6.5 | 7.4 | 8.1 | 9.3 | 10.2 | 11.0 |
| Oval | 6.3 x 4.4 | 8.0 x 5.5 | 9.2 x 6.3 | 10.1 x 6.9 | 11.5 x 7.9 | 12.7 x 8.7 | 13.7 x 9.4 |
| Cushion | 4.4 x 4.4 | 5.6 x 5.6 | 6.4 x 6.4 | 7.1 x 7.1 | 8.1 x 8.1 | 8.9 x 8.9 | 9.6 x 9.6 |
| Princess | 4.4 x 4.4 | 5.5 x 5.5 | 6.3 x 6.3 | 6.9 x 6.9 | 7.9 x 7.9 | 8.7 x 8.7 | 9.4 x 9.4 |
| Emerald cut | 5.6 x 4.0 | 7.0 x 5.0 | 8.0 x 5.7 | 8.8 x 6.3 | 10.1 x 7.2 | 11.1 x 7.9 | 12.0 x 8.5 |
| Asscher | 4.4 x 4.4 | 5.5 x 5.5 | 6.3 x 6.3 | 6.9 x 6.9 | 7.9 x 7.9 | 8.7 x 8.7 | 9.4 x 9.4 |
| Radiant | 5.2 x 4.0 | 6.5 x 5.0 | 7.4 x 5.7 | 8.2 x 6.3 | 9.4 x 7.2 | 10.3 x 7.9 | 11.1 x 8.5 |
| Pear | 6.7 x 4.4 | 8.5 x 5.5 | 9.7 x 6.3 | 10.7 x 6.9 | 12.3 x 7.9 | 13.5 x 8.7 | 14.5 x 9.4 |
| Marquise | 8.3 x 4.1 | 10.4 x 5.2 | 11.9 x 6.0 | 13.1 x 6.6 | 15.0 x 7.5 | 16.5 x 8.3 | 17.8 x 8.9 |
| Heart | 5.2 x 5.2 | 6.5 x 6.5 | 7.4 x 7.4 | 8.2 x 8.2 | 9.4 x 9.4 | 10.3 x 10.3 | 11.1 x 11.1 |
| Trillion | 5.6 x 5.6 | 7.0 x 7.0 | 8.0 x 8.0 | 8.8 x 8.8 | 10.1 x 10.1 | 11.1 x 11.1 | 12.0 x 12.0 |
| Baguette | 6.3 x 3.2 | 8.0 x 4.0 | 9.2 x 4.6 | 10.1 x 5.0 | 11.5 x 5.8 | 12.7 x 6.3 | 13.7 x 6.8 |
All sizes in mm.
Why lab grown and mined match
Lab grown diamond is chemically and structurally diamond, so density is the same. Size at a given weight depends only on density and cut. See lab grown vs natural diamond size and the methodology.
Questions
Yes. At the same carat weight and cut they measure the same, since the material and its density are the same.
A round 3 carat is about 9.3 mm across.
A round 5 carat is about 11.0 mm across.