Ring Size Conversion Table

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Inside Inside Inside Inside Number Sizes Letter Sizes    
Diameter Diameter Circumference Circumference US/Canada British Japanese Swiss
(inches) (mm) (inches) (mm) Standard Irish Equivalent Equivalent
          Australian    
          Equivalent    
0.458 11.6 1.438 36.5 0      
0.466 11.8 1.463 37.2 1/4      
0.474 12 1.488 37.8 1/2 A    
0.482 12.2 1.513 38.4 3/4 A 1/2    
0.49 12.4 1.539 39.1 1 B 1  
0.498 12.6 1.564 39.7 1 1/4 B 1/2    
0.506 12.9 1.589 40.4 1 1/2 C    
0.514 13.1 1.614 41 1 3/4 C 1/2    
0.522 13.3 1.639 41.6 2 D 2 1.5
0.53 13.5 1.664 42.3 2 1/4 D 1/2    
0.538 13.7 1.689 42.9 2 1/2 E 3 2.75
0.546 13.9 1.714 43.5 2 3/4 E 1/2    
0.554 14.1 1.74 44.2 3 F 4 4
0.562 14.3 1.765 44.8 3 1/4 F 1/2 5 5.25
0.57 14.5 1.79 45.5 3 1/2 G    
0.578 14.7 1.815 46.1 3 3/4 G 1/2 6 6.5
0.586 14.9 1.84 46.7 4 H  7  
0.594 15.1 1.865 47.4 4 1/4 H 1/2   7.75
0.602 15.3 1.89 48 4 1/2 I  8  
0.61 15.5 1.915 48.7 4 3/4 J   9
0.618 15.7 1.941 49.3 5 J 1/2 9  
0.626 15.9 1.966 49.9 5 1/4 K   10
0.634 16.1 1.991 50.6 5 1/2 K 1/2 10  
0.642 16.3 2.016 51.2 5 3/4 L   11.75
0.65 16.5 2.041 51.8 6 L 1/2 11 12.75
0.658 16.7 2.066 52.5 6 1/4 M  12  
0.666 16.9 2.091 53.1 6 1/2 M 1/2 13 14
0.674 17.1 2.116 53.8 6 3/4 N    
0.682 17.3 2.141 54.4 7 N 1/2 14 15.25
0.69 17.5 2.167 55 7 1/4 O