Rings Sizes

US UK Inside Diameter Inside Circumference
4 H 14.9mm 46.8mm
4.5 I 1/2 15.2mm 48.0mm
5 J 1/2 15.7mm 49.3mm
5.5 K 1/2 16.1mm 50.6mm
6 L 1/2 16.5mm 51.9mm
6.5 M 1/2 16.9mm 53.1mm
7 N 1/2 17.3mm 54.4mm
7.5 O 1/2 17.7mm 55.7mm
8 P 1/2 18.1mm 57.0mm
8.5 Q 1/2 18.5mm 58.3mm
9 R 1/2 19.0mm 59.5mm
9.5 S 1/2 19.4mm 60.8mm
10 T 1/2 19.8mm 62.1mm
10.5 U 1/2 20.2mm 63.4mm
11 V 1/2 20.6mm 64.6mm
11.5 W 1/2 21.0mm 65.9mm
12 Y 21.4mm 67.2mm
12.5 Z 21.8mm 68.5mm
13 Z+ 22.2mm 69.7mm