Kunzite size chart: carat to mm for every shape

By HeyGema™ · Updated November 5, 2026

In short

A 1 carat round kunzite measures about 6.7 mm across, against 6.5 mm for a 1 carat diamond. Kunzite is lighter than diamond (3.18 against 3.52), so the same weight gives a bigger stone, 3% wider across.

6.7 mm1 carat round kunzite
3.18density, g/cm3
6.5 to 7hardness, Mohs

Carat to mm calculator

ShapeGemCarat

About 6.7 x 6.7 mm

An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.

Kunzite size chart: carat to mm

Face-up length and width in mm of a well-cut kunzite at each weight and shape. Kunzite is lighter than diamond (3.18 against 3.52), so the same weight gives a bigger stone, 3% wider across.

Weight	Round	Oval	Cushion	Emerald cut	Pear	Princess
0.25 ct	4.2	5.2 x 3.6	3.6 x 3.6	4.6 x 3.3	5.5 x 3.6	3.6 x 3.6
0.5 ct	5.3	6.6 x 4.5	4.6 x 4.6	5.7 x 4.1	7.0 x 4.5	4.5 x 4.5
0.75 ct	6.1	7.5 x 5.2	5.3 x 5.3	6.6 x 4.7	8.0 x 5.2	5.2 x 5.2
1 ct	6.7	8.3 x 5.7	5.8 x 5.8	7.2 x 5.2	8.8 x 5.7	5.7 x 5.7
1.5 ct	7.6	9.5 x 6.5	6.6 x 6.6	8.3 x 5.9	10.1 x 6.5	6.5 x 6.5
2 ct	8.4	10.4 x 7.2	7.3 x 7.3	9.1 x 6.5	11.1 x 7.2	7.2 x 7.2
3 ct	9.6	11.9 x 8.2	8.4 x 8.4	10.4 x 7.5	12.7 x 8.2	8.2 x 8.2
4 ct	10.6	13.1 x 9.0	9.2 x 9.2	11.5 x 8.2	14.0 x 9.0	9.0 x 9.0
5 ct	11.4	14.2 x 9.7	9.9 x 9.9	12.4 x 8.8	15.0 x 9.7	9.7 x 9.7
10 ct	14.4	17.8 x 12.3	12.5 x 12.5	15.6 x 11.1	18.9 x 12.3	12.3 x 12.3

Length x width in mm. A round stone shows one number, its diameter.

mm to carat for a round kunzite

If you know the size, this is the weight. Measure across the widest point of the stone, face up.

4 mm: Weight: 0.22 ct

5 mm: Weight: 0.42 ct

6 mm: Weight: 0.73 ct

7 mm: Weight: 1.15 ct

8 mm: Weight: 1.72 ct

9 mm: Weight: 2.45 ct

10 mm: Weight: 3.37 ct

12 mm: Weight: 5.82 ct

Diameter	Weight
4 mm	0.22 ct
5 mm	0.42 ct
6 mm	0.73 ct
7 mm	1.15 ct
8 mm	1.72 ct
9 mm	2.45 ct
10 mm	3.37 ct
12 mm	5.82 ct

Kunzite against diamond

How wide a round kunzite is next to a round diamond of the same weight.

0.5 ct: Kunzite: 5.3 mm; Diamond: 5.1 mm; Difference: +0.2 mm

1 ct: Kunzite: 6.7 mm; Diamond: 6.5 mm; Difference: +0.2 mm

2 ct: Kunzite: 8.4 mm; Diamond: 8.1 mm; Difference: +0.3 mm

3 ct: Kunzite: 9.6 mm; Diamond: 9.3 mm; Difference: +0.3 mm

5 ct: Kunzite: 11.4 mm; Diamond: 11.0 mm; Difference: +0.4 mm

Weight	Kunzite	Diamond	Difference
0.5 ct	5.3 mm	5.1 mm	+0.2 mm
1 ct	6.7 mm	6.5 mm	+0.2 mm
2 ct	8.4 mm	8.1 mm	+0.3 mm
3 ct	9.6 mm	9.3 mm	+0.3 mm
5 ct	11.4 mm	11.0 mm	+0.4 mm

Kunzite properties

Density used in the charts: Value: 3.18 g/cm3 (range 3.18)

Hardness (Mohs): Value: 6.5 to 7

Refractive index: Value: 1.660 to 1.676

Property	Value
Density used in the charts	3.18 g/cm3 (range 3.18)
Hardness (Mohs)	6.5 to 7
Refractive index	1.660 to 1.676

A pink to lilac spodumene. Cleaves easily, so it needs a protective setting.

Kunzite at each weight

Questions

A 1 carat round kunzite is about 6.7 mm across. An oval is 8.3 x 5.7 mm and a cushion cut 5.8 x 5.8 mm.

Yes. A 1 carat kunzite is 6.7 mm and a 1 carat diamond 6.5 mm. Kunzite is lighter than diamond (3.18 against 3.52), so the same weight gives a bigger stone, 3% wider across.

A 6 mm round kunzite weighs about 0.73 carat. An 8 mm stone weighs about 1.72 carat.

A 5 carat round kunzite is about 11.4 mm across (0.45 inches).

A carat is a weight, 0.2 grams. Gems differ in density, so a gram of a dense gem takes up less space than a gram of a light one. Dense stones face up smaller for their weight.