Zircon size chart: carat to mm for every shape
By HeyGema™ · Updated
In short
A 1 carat round zircon measures about 5.9 mm across, against 6.5 mm for a 1 carat diamond. Zircon is denser than diamond (4.69 against 3.52), so it packs more weight into less space and faces up 9% narrower for the same weight.
- 5.9 mm1 carat round zircon
- 4.69density, g/cm3
- 6 to 7.5hardness, Mohs
Carat to mm calculator
About 5.9 x 5.9 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
Zircon size chart: carat to mm
Face-up length and width in mm of a well-cut zircon at each weight and shape. Zircon is denser than diamond (4.69 against 3.52), so it packs more weight into less space and faces up 9% narrower for the same weight.
| Weight | Round | Oval | Cushion | Emerald cut | Pear | Princess |
|---|---|---|---|---|---|---|
| 0.25 ct | 3.7 | 4.6 x 3.1 | 3.2 x 3.2 | 4.0 x 2.86 | 4.9 x 3.1 | 3.1 x 3.1 |
| 0.5 ct | 4.7 | 5.8 x 4.0 | 4.0 x 4.0 | 5.0 x 3.6 | 6.1 x 4.0 | 4.0 x 4.0 |
| 0.75 ct | 5.3 | 6.6 x 4.5 | 4.6 x 4.6 | 5.8 x 4.1 | 7.0 x 4.5 | 4.5 x 4.5 |
| 1 ct | 5.9 | 7.3 x 5.0 | 5.1 x 5.1 | 6.4 x 4.5 | 7.7 x 5.0 | 5.0 x 5.0 |
| 1.5 ct | 6.7 | 8.3 x 5.7 | 5.8 x 5.8 | 7.3 x 5.2 | 8.8 x 5.7 | 5.7 x 5.7 |
| 2 ct | 7.4 | 9.2 x 6.3 | 6.4 x 6.4 | 8.0 x 5.7 | 9.7 x 6.3 | 6.3 x 6.3 |
| 3 ct | 8.5 | 10.5 x 7.2 | 7.3 x 7.3 | 9.2 x 6.6 | 11.1 x 7.2 | 7.2 x 7.2 |
| 4 ct | 9.3 | 11.5 x 7.9 | 8.1 x 8.1 | 10.1 x 7.2 | 12.3 x 7.9 | 7.9 x 7.9 |
| 5 ct | 10.0 | 12.4 x 8.5 | 8.7 x 8.7 | 10.9 x 7.8 | 13.2 x 8.5 | 8.5 x 8.5 |
| 10 ct | 12.6 | 15.7 x 10.8 | 11.0 x 11.0 | 13.7 x 9.8 | 16.6 x 10.8 | 10.8 x 10.8 |
Length x width in mm. A round stone shows one number, its diameter.
mm to carat for a round zircon
If you know the size, this is the weight. Measure across the widest point of the stone, face up.
- 4 mm
- Weight: 0.32 ct
- 5 mm
- Weight: 0.62 ct
- 6 mm
- Weight: 1.07 ct
- 7 mm
- Weight: 1.7 ct
- 8 mm
- Weight: 2.54 ct
- 9 mm
- Weight: 3.62 ct
- 10 mm
- Weight: 4.97 ct
- 12 mm
- Weight: 8.58 ct
Zircon against diamond
How wide a round zircon is next to a round diamond of the same weight.
- 0.5 ct
- Zircon: 4.7 mm
- Diamond: 5.1 mm
- Difference: -0.5 mm
- 1 ct
- Zircon: 5.9 mm
- Diamond: 6.5 mm
- Difference: -0.6 mm
- 2 ct
- Zircon: 7.4 mm
- Diamond: 8.1 mm
- Difference: -0.7 mm
- 3 ct
- Zircon: 8.5 mm
- Diamond: 9.3 mm
- Difference: -0.8 mm
- 5 ct
- Zircon: 10.0 mm
- Diamond: 11.0 mm
- Difference: -1.0 mm
Zircon properties
- Density used in the charts
- Value: 4.69 g/cm3 (range 4.60 to 4.70 (high zircon; low zircon is 3.9 to 4.1))
- Hardness (Mohs)
- Value: 6 to 7.5
- Refractive index
- Value: 1.925 to 1.984
A natural gem, not cubic zirconia. We use the density of high zircon, so it faces up smaller than a diamond of the same weight; low zircon is lighter.