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International Ring Size Conversion Chart

U.S. Size Diameter
in Inches
Diameter
in MM
Metric MM
Equivalent
British French German Japanese Swiss
4 .585 14.86 46.5 H 1/2 - 15 7  
4 1/4 - 15.04 47.1 I 47 3/4     7 3/4
4 1/2 .601 15.27 47.8 I 1/2 - 15 1/4 8  
4 5/8 - 15.40 48.1 J 49 15 1/2   9
4 3/4 - 15.53 48.4 - -      
5 .618 15.70 49.0 J 1/2 - 15 3/4 9  
5 1/8 - 15.80 49.3 K 50     10
5 1/4 - 15.90 49.6 - -      
5 3/8 - 16.0 50.0 K 1/2 -   10  
5 1/2 .634 16.10 50.3 L 51 3/4 16   11 3/4
5 3/4 - 16.30 50.9 - -      
5 7/8 - 16.41 51.3 L 1/2 -      
6 .650 16.51 51.5 M 52 3/4 16 1/2 12 12 3/4
6 1/4 - 16.71 52.2 M 1/2 -      
6 1/2 .666 16.92 52.8 N 54 17 13 14
6 3/4 - 17.13 53.4 N 1/2 -      
7 .683 17.35 54.0 O 55 1/4 17 1/4 14 15 1/4
7 1/4 - 17.45 54.7 O 1/2 -      
7 1/2 .699 17.75 55.3 P 56 1/2 17 3/4 15 16 1/2
7 3/4 - 17.97 55.9 P 1/2 -      
8 .716 18.19 56.6 Q 57 3/4 18 16 17 3/4
8 1/4 - 18.35 57.2 Q 1/2 -      
8 1/2 .732 18.53 57.8 - - 18 1/2 17  
8 5/8 - 18.61 58.4 R 59     19
8 3/4 - 18.69 58.4 - -      
8 7/8 - 18.80 59.0 R 1/2 -      
9 .748 18.89 59.1 - - 19 18  
9 1/8 - 19.10 59.4 S 60 1/4     20 1/4
9 1/4 - 19.22 59.7 - -      
9 3/8 - 19.31 60.0 S 1/2 -      
9 1/2 .764 19.41 60.3 - - 19 1/2 19  
9 5/8 - 19.51 60.6 T 61 1/2     21 1/2
9 3/4 - 19.62 60.9 - -      
10 .781 19.84 61.6 T 1/2 - 20 20  
10 1/4 - 20.02 62.2 U 62 3/4   21 22 3/4
10 1/2 .797 20.20 62.8 U 1/2 - 20 1/4 22  
10 5/8 - 20.32 63.1 V 63     23 3/4
10 3/4 - 20.44 63.5 - -      
11 .814 20.68 64.1 V 1/2 - 20 3/4 23  
11 1/8 - 20.76 64.3 W 65     25
11 1/4 - 20.85 64.7 - -      
11 3/8 - 20.94 65.0 W 1/2 -      
11 1/2 - 21.08 65.3 - - 21 24  
11 5/8 .830 21.18 65.7 X 66 1/4     26 1/4
11 3/4 - 21.24 66.0 - -      
11 7/8 - 21.30 66.3 X 1/2 -      
12 .846 21.49 66.6 Y 67 1/2 21 1/4 25 27 1/2
12 1/4 - 21.69 67.2 Y 1/2 -      
12 1/2 .862 21.89 67.9 Z 68 3/4 21 3/4 26 28 3/4
12 3/4 - 22.10 68.5 Z 1/2 -      
13 .879 22.33 69.1 - - 22 27