International Ring Size Conversion Chart Inside Diameter  Inside Circumference Sizes MM Inches MM Inches British & Australian  US & Canada French & Russian German Japanese Swiss 9.91 0.390 31.13 1.22 - 0000 - - - - 10.72 0.442 33.68 1.39 - 00 - - - - 11.53 0.454 36.22 1.43 - 0 - - - - 11.95 0.474 37.54 1.49 A 1/2 - - - - 12.18 0.482 38.26 1.51 A 1/2 3/4 - - - - 12.37 0.487 38.86 1.53 B 1 - - 1 - 12.60 0.496 39.58 1.56 B ...