Size (inches)

Size (mm)

Diameter (mm)

U.S.A. size

Japanese size

British size

German size

Swiss size

1 14/16

48

15.27

4 1/2

8

I - 1/2

15 1/4

--

1 15/16

49

15.70

5

9

J 1/2

15 3/4

--

2

51

16.10

5 1/2

11

L

16

11 3/4

2 1/16

52

16.51

6

12

M

16 1/2

12 3/4

2 2/16

53

16.92

6 1/2

13

N

17

14

2 3/16

55

17.35

7

14

O

17 1/4

15 1/4

2 4/16

56

17.75

7 1/2

15

P

17 3/4

16 1/2

2 5/16

57

18.19

8

16

Q

18

17 3/4

2 6/16

58

18.53

8 1/2

17

Q 1/2

18 1/2

--

2 7/16

59

18.89

9

18

R 1/2

19

--

2 8/16

61

19.41

9 1/2

19

S 1/2

19 1/2

--

2 9/16

62

19.84

10

20

T 1/2

20

--

2 10/16

63

20.20

10 1/2

22

U 1/2

20 1/4

--

2 11/16

65

20.68

11

23

V 1/2

20 3/4

--

2 12/16

66

21.08

11 1/2

24

W 1/2

21

--

2 13/16

68

21.49

12

25

Y

21 1/4

27 1/2

2 14/16

69

21.89

12 1/2

26

Z

21 3/4

28 3/4

2 15/16

70

22.33

13

27

--

22

--