Ring size

Inside diameter (mm)

Inside circumference (mm)

10

15.9

50

11

16.2

51

12

16.6

52

13

16.9

53

14

17.2

54

15

17.5

55

16

17.8

56

17

18.1

57

18

18.5

58

19

18.8

59

20

19.1

60

21

19.4

61

22

19.7

62

23

20.1

63

24

20.4

64