Ring Diameter (MM) USA/Canada UK France Germany Japan Switzerland
14.0 mm. 3 F 44 14 4 4
14.4 mm. 3.5 G 45 ½ 14 ½ ½
14.8 mm. 4 ½ 46 ½ 15 7
½
15.2 mm. 4.5 ½
47 ¾
15 ¼
8 8
15.6 mm. 5 ½ 49
15 ¾
9
9 ½
16.0 mm. 5.5 L
50 ¾
16
10 ½
10 ¾
16.5 mm. 6 M
51 ½
16½
12
12 ¾
16.9 mm. 6.5 N
52 ¾
17 13 14
17.3 mm. 7 O 54 17 ¼ 14
15 ¼
17.7 mm. 7.5 P
55 ¼
17 ¾
15
16 ½
18.2 mm. 8 Q
56 ¾
18 16
17 ¾
18.6 mm. 8.5 Q ½ 58
18 ½
17
18 ½
19.0 mm. 9 R ½
59 ¼
19 18 20
19.4 mm. 9.5 S ½
60 ¾
19 ½
19 21
19.8 mm. 10 T ½
61 ¾
20 20
21 ¾
20.2 mm. 10.5 U ½
62 ¾
20 ¼
22
22 ¾
20.6 mm. 11 V ½
64 ¼
20 ¾
23 24
21mm. 11.5 W ½ 66 21 24
25 ¾
21.4 mm. 12 Y
67 ¼
21 ¼
25
27 ½
21.8 mm. 12.5 Z 68
21 ¾
26
28 ¾
22.2 mm. 13 Z +1 69 22 27
29 ¼
22.6 mm. 13.5 Z +1.5 71 22.6 - 31