U.S.  Size

Diameter
in Inches

Diameter
in MM

Metric MM
Equivalent

British 

French 

German 

Japanese 

Swiss 

0000

.390

9.91

-

00

.422

10.72

-

0

.454

11.53

-

1/2

.474

11.95

A

3/4

.482

12.18

A 1/2

1

.487

12.37

38.9

B

1

1 1/4

-

12.60

39.6

B 1/2

1 1/2

.503

12.78

40.2

C

1 3/4

-

13.00

40.8

C 1/2

2

.520

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

.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

.553

14.05

44.0

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

.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

.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