Inside diameter mm

Inside circumference inches

Inside diameter inches

Inside circumference mm

US Ring Size

British & Australian

14.9

1.840

0.586

46.7

4

H

15.3

1.890

0.602

48

4 1/2

H ½

15.7

1.941

0.618

49.3

5

J ½

16.1

1.991

0.634

50.6

5 1/2

K ½

16.5

2.041

0.650

51.8

6

L ½

16.9

2.091

0.666

53.1

6 1/2

M1/2

17.3

2,141

0.682

54.4

7

N 1/2

17.7

2.192

0.698

55.7

7 ½

O 1/2

18.1

2.242

0.714

56.9

8

P ½

18.5

2.292

0.730

58.2

8 ½

Q 1/2

18.9

2.2342

0.746

59.5

9

R ½

19.4

2.393

0.762

60.8

9 ½

S 1/2

19.8

2.443

0.778

62.1

10

T 1/2

20.2

2.493

0.794

63.3

10 ½

U ½

20.6

2.543

0.810

64.6

11

V ½

21

2.594

0.826

65.9

11 ½

W ½

21.4

2.644

0.842

67.2

12

X 1/2