Ring Size Conversions

 

Inside Diameter
(inches
)

Inside Diameter
(mm)

Inside Circumference
(inches)

Inside Circumference
(mm)

Number Sizes
US/Canada
Standard

Letter Sizes
British Irish Australian
NZ Equivalent

 
0.570 14.5 1.790 45.5 3 1/2 G
0.578 14.7 1.815 46.1 3 3/4 G 1/2
0.586 14.9 1.840 46.7 4
0.594 15.1 1.865 47.4 4 1/4 H 1/2
0.602 15.3 1.890 48.0 4 1/2
0.610 15.5 1.915 48.7 4 3/4 J
0.618 15.7 1.941 49.3 5 J 1/2
0.626 15.9 1.966 49.9 5 1/4 K
0.634 16.1 1.991 50.6 5 1/2 K 1/2
0.642 16.3 2.016 51.2 5 3/4 L
0.650 16.5 2.041 51.8 6 L 1/2
0.658 16.7 2.066 52.5 6 1/4
0.666 16.9 2.091 53.1 6 1/2 M 1/2
0.674 17.1 2.116 53.8 6 3/4 N
0.682 17.3 2.141 54.4 7 N 1/2
0.690 17.5 2.167 55.0 7 1/4
0.698 17.7 2.192 55.7 7 1/2 O 1/2
0.706 17.9 2.217 56.3 7 3/4
0.714 18.1 2.242 56.9 8 P 1/2
0.722 18.3 2.267 57.6 8 1/4
0.730 18.5 2.292 58.2 8 1/2 Q 1/2
0.738 18.7 2.317 58.9 8 3/4 R
0.746 18.9 2.342 59.5 9 R 1/2
0.754 19.2 2.368 60.1 9 1/4 S
0.762 19.4 2.393 60.8 9 1/2 S 1/2
0.770 19.6 2.418 61.4 9 3/4 T
0.778 19.8 2.443 62.1 10 T 1/2
0.786 20.0 2.468 62.7 10 1/4 U
0.794 20.2 2.493 63.3 10 1/2 U 1/2
0.802 20.4 2.518 64.0 10 3/4 V
0.810 20.6 2.543 64.6 11 V 1/2
0.818 20.8 2.569 65.2 11 1/4 W
0.826 21.0 2.594 65.9 11 1/2 W 1/2
0.834 21.2 2.619 66.5 11 3/4 X
0.842 21.4 2.644 67.2 12 X 1/2
0.850 21.6 2.669 67.8 12 1/4
0.858 21.8 2.694 68.4 12 1/2 Z
0.866 22.0 2.719 69.1 12 3/4 Z 1/2
0.874 22.2 2.744 69.7 13  
0.882 22.4 2.769 70.3 13 1/4 Z1
0.890 22.6 2.795 71.0 13 1/2  
0.898 22.8 2.820 71.6 13 3/4 Z2
0.906 23.0 2.845 72.3 14 Z3
0.914 23.2 2.870 72.9 14 1/4  
0.922 23.4 2.895 73.5 14 1/2 Z4