Aquamarine size chart: carat to mm for every shape
By HeyGema™ · Updated
In short
A 1 carat round aquamarine measures about 7.0 mm across, against 6.5 mm for a 1 carat diamond. Aquamarine is lighter than diamond (2.70 against 3.52), so the same weight gives a bigger stone, 9% wider across.
- 7.0 mm1 carat round aquamarine
- 2.70density, g/cm3
- 7.5 to 8hardness, Mohs
Carat to mm calculator
About 7.0 x 7.0 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
Aquamarine size chart: carat to mm
Face-up length and width in mm of a well-cut aquamarine at each weight and shape. Aquamarine is lighter than diamond (2.70 against 3.52), so the same weight gives a bigger stone, 9% wider across.
| Weight | Round | Oval | Cushion | Emerald cut | Pear | Princess |
|---|---|---|---|---|---|---|
| 0.25 ct | 4.4 | 5.5 x 3.8 | 3.9 x 3.9 | 4.8 x 3.4 | 5.8 x 3.8 | 3.8 x 3.8 |
| 0.5 ct | 5.6 | 6.9 x 4.8 | 4.9 x 4.9 | 6.1 x 4.3 | 7.4 x 4.8 | 4.8 x 4.8 |
| 0.75 ct | 6.4 | 7.9 x 5.5 | 5.6 x 5.6 | 6.9 x 5.0 | 8.4 x 5.5 | 5.5 x 5.5 |
| 1 ct | 7.0 | 8.7 x 6.0 | 6.1 x 6.1 | 7.6 x 5.5 | 9.3 x 6.0 | 6.0 x 6.0 |
| 1.5 ct | 8.1 | 10.0 x 6.9 | 7.0 x 7.0 | 8.8 x 6.3 | 10.6 x 6.9 | 6.9 x 6.9 |
| 2 ct | 8.9 | 11.0 x 7.6 | 7.7 x 7.7 | 9.6 x 6.9 | 11.7 x 7.6 | 7.6 x 7.6 |
| 3 ct | 10.2 | 12.6 x 8.7 | 8.8 x 8.8 | 11.0 x 7.9 | 13.4 x 8.7 | 8.7 x 8.7 |
| 4 ct | 11.2 | 13.9 x 9.5 | 9.7 x 9.7 | 12.1 x 8.7 | 14.7 x 9.5 | 9.5 x 9.5 |
| 5 ct | 12.0 | 14.9 x 10.3 | 10.5 x 10.5 | 13.1 x 9.3 | 15.9 x 10.3 | 10.3 x 10.3 |
| 10 ct | 15.2 | 18.8 x 12.9 | 13.2 x 13.2 | 16.5 x 11.8 | 20.0 x 12.9 | 12.9 x 12.9 |
Length x width in mm. A round stone shows one number, its diameter.
mm to carat for a round aquamarine
If you know the size, this is the weight. Measure across the widest point of the stone, face up.
- 4 mm
- Weight: 0.18 ct
- 5 mm
- Weight: 0.36 ct
- 6 mm
- Weight: 0.62 ct
- 7 mm
- Weight: 0.98 ct
- 8 mm
- Weight: 1.46 ct
- 9 mm
- Weight: 2.08 ct
- 10 mm
- Weight: 2.86 ct
- 12 mm
- Weight: 4.94 ct
Aquamarine against diamond
How wide a round aquamarine is next to a round diamond of the same weight.
- 0.5 ct
- Aquamarine: 5.6 mm
- Diamond: 5.1 mm
- Difference: +0.5 mm
- 1 ct
- Aquamarine: 7.0 mm
- Diamond: 6.5 mm
- Difference: +0.6 mm
- 2 ct
- Aquamarine: 8.9 mm
- Diamond: 8.1 mm
- Difference: +0.8 mm
- 3 ct
- Aquamarine: 10.2 mm
- Diamond: 9.3 mm
- Difference: +0.9 mm
- 5 ct
- Aquamarine: 12.0 mm
- Diamond: 11.0 mm
- Difference: +1.0 mm
Aquamarine properties
- Density used in the charts
- Value: 2.70 g/cm3 (range 2.68 to 2.74)
- Hardness (Mohs)
- Value: 7.5 to 8
- Refractive index
- Value: 1.567 to 1.590
A beryl. Light, so it faces up bigger than a diamond of the same weight.