Ring size reference

US size Diameter (mm) perimeter (mm)
4 14.8 mm 46.7 mm
4 1/2 15.2 mm 48 mm
5 15.7 mm 49.3 mm
5 1/2 16.1 mm 50.6 mm
6 16.5 mm 51.8 mm
6 1/2 16.9 mm 53.1 mm
7 17.3 mm 54.4 mm
7 1/2 17.7 mm 55.7 mm
8 18.1 mm 56.9 mm
8 1/2 18.5 mm 58.2 mm
9 18.9 mm 59.5 mm
9 1/2 19.4 mm 60.8 mm
10 19.8 mm 62.1 mm
10 1/2 20.2 mm 63.3 mm
11 20.6 mm 64.6 mm
12 21.4 mm 67.2 mm