Here is a hand with different chain thicknesses to help you find the thickness you are looking for.

MM to Centimeters

1 mm = 0.1 Centimeter

2 mm = 0.2 Centimeter

3 mm = 0.3 Centimeter

4 mm = 0.4 Centimeter

5 mm = 0.5 Centimeter

6 mm = 0.6 Centimeter

7 mm = 0.7 Centimeter

8 mm = 0.8 Centimeter

9 mm = 0.9 Centimeter

10 mm = 1 Centimeter

Here is a picture of different chain lengths in inches to help you find what length your looking for.

Inches to Cm

16 inches = 40.64 cm

18 inches = 45.72 cm

20 inches = 50.8 cm

22 inches = 55.88 cm

24 inches = 60.96 cm

30 inches = 76.2 cm