US Size UK Size Circumference Diameter
5 J 49mm 15.49mm
5.5 L 51mm 16.10mm
6 M 52mm 16.51mm
6.5 N 53mm 16.92mm
7 O 55mm 17.35mm
8 Q 57mm 18.19mm
9 R1/2 59mm 18.89mm
10 T1/2 62mm 19.84mm
11.5 W1/2 66mm 21.08mm
12.5 Z 68mm 21.89mm
14 Z3 72mm 23mm
15 Z5 75mm 24mm