International Ring Size Conversion Table

USĀ  & Canada Diameter
(inch)
Diameter
(mm)
Metric
(mm)
British French German Japanese Swiss
0 0.39 9.91
00 0.422 10.72
000 0.454 11.53
1/4 0.474 11.95 A
3/4 0.482 12.18 A 1/2
1 0.487 12.37 38.9 B 1
1 1/4 12.6 39.6 B 1/2
1 1/2 0.503 12.78 40.2 C
1 3/4 13 40.8 C 1/2
2 0.52 13.21 41.5 D 41 1/2 13 1/2 2 1 1/2
2 1/4 13.41 42.1 D 1/2
2 1/2 0.536 13.61 42.7 E 42 3/4 13 3/4 3 2 3/4
2 3/4 13.83 43.4 E 1/2
3 0.553 14.05 44 F 44 14 4 4
3 1/8 14.15 44.3 F 1/2
3 1/4 14.25 44.6
3 3/8 14.36 44.9 G 45 1/4 5 5 1/4
3 1/2 0.569 14.45 45.2 14 1/2
3 5/8 14.56 45.6 G 1/2 6
3 3/4 14.65 45.9 H 46 1/2 6 1/2
4 0.585 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 0.601 15.27 47.8 I 1/2 15 1/4 8
4 5/8 15.4 48.1 J 49 15 1/2 9
4 3/4 15.53 48.4
5 0.618 15.7 49 J 1/2 15 3/4 9
5 1/8 15.8 49.3 K 50 10
5 1/4 15.9 49.6
5 3/8 16 50 K 1/2 10
5 1/2 0.634 16.1 50.3 L 51 3/4 16 11 3/4
5 3/4 16.3 50.9
5 7/8 16.41 51.3 L 1/2
6 0.65 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 0.666 16.92 52.8 N 54 17 13 14
6 3/4 17.13 53.4 N 1/2
7 0.683 17.35 54 O 55 1/4 17 1/4 14 15 1/4
7 1/4 17.45 54.7 O 1/2
7 1/2 0.699 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 0.716 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 0.732 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 18.8 59 R 1/2
9 0.748 18.89 59.1 19 18
9 1/8 19.1 59.4 S 60 1/4 20 1/4
9 1/4 19.22 59.7
9 3/8 19.31 60 S 1/2
9 1/2 0.764 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 0.781 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 0.797 20.2 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 0.814 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 W 1/2
11 1/2 21.08 65.3 21 24
11 5/8 0.83 21.18 65.7 X 66 1/4 26 1/4
11 3/4 21.24 66
11 7/8 21.3 66.3 X 1/2
12 0.846 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 0.862 21.89 67.9 Z 68 3/4 21 3/4 26 28 3/4
12 3/4 22.1 68.5 Z 1/2
13 0.879 22.33 69.1 22 27

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Magic of the Lost Continent