Ring Sizes Conversion Chart
 
Diameter
inside in mm 		Circumfer.
inside in mm 		USA
Canada		 England
Australia		 Japan Swiss
14.9 46.7 4 H 7  
15.1 47.4 4 1/4 H 1/2   7.75
15.3 48.0 4 1/2 I 8  
15.5 48.7 4 3/4 J   9.00
15.7 49.3 5 J 1/2 9  
15.9 49.9 5 1/4 K   10.00
16.1 50.6 5 1/2 K 1/2 10  
16.3 51.2 5 3/4 L   11.75
16.5 51.8 6 L 1/2 11 12.75
16.7 52.5 6 1/4 M 12  
16.9 53.1 6 1/2 M 1/2 13 14.00
17.1 53.8 6 3/4 N    
17.3 54.4 7 N 1/2 14 15.25
17.5 55.0 7 1/4 O    
17.7 55.7 7 1/2 O 1/2 15 16.50
17.9 56.3 7 3/4 P    
18.1 56.9 8 P 1/2 16 17.75
18.3 57.6 8 1/4 Q    
18.5 58.2 8 1/2 Q 1/2 17  
18.7 58.9 8 3/4 R   19
18.9 59.5 9 R 1/2 18  
19.2 60.1 9 1/4 S   20.25
19.4 60.8 9 1/2 S 1/2 19  
19.6 61.4 9 3/4 T   21.50
19.8 62.1 10 T 1/2 20  
20.0 62.7 10 1/4 U 21  
20.2 63.3 10 1/2 U 1/2 22 22.75
20.4 64.0 10 3/4 V    
20.6 64.6 11 V 1/2 23  
20.8 65.2 11 1/4 W   25
21.0 65.9 11 1/2 W 1/2 24  
21.2 66.5 11 3/4 X    
21.4 67.2 12 X 1/2 25 27.50
21.6 67.8 12 1/4 Y    
21.8 68.4 12 1/2 Z 26 28.75
22.0 69.1 12 3/4 Z 1/2    
22.2 69.7 13   27