Lab grown vs natural diamond size: is there a difference?
By HeyGema™ · Updated
In short
There is no size difference. Lab grown and natural diamonds are the same material with the same density, so 1 carat is 6.5 mm round in both. Moissanite is a different material and differs from both.
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.
Why the size is the same
A carat is a unit of weight (200 milligrams). The size of a stone at a given weight depends on its density and cut. Lab grown diamond is chemically the same as mined diamond, so it has the same density (3.52) and a well-cut stone of each weight measures the same.
- 0.5 ct
- Round lab grown or natural: 5.1 mm
- Round moissanite (true weight): 5.3 mm
- 1 ct
- Round lab grown or natural: 6.5 mm
- Round moissanite (true weight): 6.6 mm
- 1.5 ct
- Round lab grown or natural: 7.4 mm
- Round moissanite (true weight): 7.6 mm
- 2 ct
- Round lab grown or natural: 8.1 mm
- Round moissanite (true weight): 8.4 mm
- 3 ct
- Round lab grown or natural: 9.3 mm
- Round moissanite (true weight): 9.6 mm
- 4 ct
- Round lab grown or natural: 10.2 mm
- Round moissanite (true weight): 10.5 mm
- 5 ct
- Round lab grown or natural: 11.0 mm
- Round moissanite (true weight): 11.4 mm
Where real stones differ
Two stones of the same weight can differ a little in width, from the cut alone: a deep stone measures smaller across, a shallow one larger. That varies between individual stones whether they are lab grown or natural. Compare the millimeter measurements on the grading report and not only the carat weight. See the diamond carat size chart and the moissanite vs diamond size page.