Ring Size Conversion Table

US &

Canada

UK, Ireland

Australia

Japan

Swiss

Diameter

(inside mm)

Circumference

(inside mm)

3

F

4

4.00

14.1

44.2

3 1/4

F 1/2

5

5.25

14.3

44.8

3 1/2

G

14.5

45.5

3 3/4

G 1/2

6

6.50

14.7

46.1

4

H 

7

14.9

46.7

4 1/4

H 1/2

7.75

15.1

47.4

4 1/2

I 

8

15.3

48.0

4 3/4

J

9.00

15.5

48.7

5

J 1/2

9

15.7

49.3

5 1/4

K

10.00

15.9

49.9

5 1/2

K 1/2

10

16.1

50.6

5 3/4

L

11.75

16.3

51.2

6

L 1/2

11

12.75

16.5

51.8

6 1/4

M 

12

16.7

52.5

6 1/2

M 1/2

13

14.00

16.9

53.1

6 3/4

N

17.1

53.8

7

N 1/2

14

15.25

17.3

54.4

7 1/4

O 

17.5

55.0

7 1/2

O 1/2

15

16.50

17.7

55.7

7 3/4

P 

17.9

56.3

8

P 1/2

16

17.75

18.1

56.9

8 1/4

Q 

18.3

57.6

8 1/2

Q 1/2

17

18.5

58.2

8 3/4

R

19

18.7

58.9

9

R 1/2

18

18.9

59.5

9 1/4

S

20.25

19.2

60.1

9 1/2

S 1/2

19

19.4

60.8

9 3/4

T

21.5

19.6

61.4

10

T 1/2

20

19.8

62.1

10 1/4

U

21

20.0

62.7

10 1/2

U 1/2

22

22.75

20.2

63.3

10 3/4

V

20.4

64.0

11

V 1/2

23

20.6

64.6

11 1/4

W

25

20.8

65.2

11 1/2

W 1/2

24

21.0

65.9

11 3/4

X

21.2

66.5

12

X 1/2

25

27.50

21.4

67.2

12 1/4

Y 

21.6

67.8

12 1/2

Z

26

28.75

21.8

68.4

12 3/4

Z 1/2

22.0

69.1

13

27

22.2

69.7