Ring size conversion chart

INSIDE DIAMETERINSIDE CIRCUMFERENCESIZES
MMINCHESMMINCHESBRITISH & AUSTRALIANUS & CANADAFRENCH & RUSSIANJAPANESE
15.70 0.618 49.32 1.94 J 1/2 5 - 9
15.80 0.622 49.64 1.95 K 5 1/8 50 -
15.90 0.626 49.95 1.97 K 1/4 5 1/4 - -
16.00 0.630 50.27 1.98 K 1/2 5 3/8 - 10
16.10 0.634 50.58 1.99 L 5 1/2 51 3/4 -
16.30 0.642 51.24 2.02 L 1/4 5 3/4 - -
16.41 0.646 51.55 2.03 L 1/2 5 7/8 52 -
16.51 0.650 51.87 2.05 M 6 - 12
16.71 0.658 52.50 2.07 M 1/2 6 1/4 53 -
16.92 0.666 53.16 2.09 N 6 1/2 54 13
17.13 0.674 53.82 2.12 N 1/2 6 3/4 - -
17.35 0.683 54.51 2.15 O 7 55 14
17.45 0.687 54.82 2.16 O 1/2 7 1/4 - -
17.75 0.699 55.76 2.20 P 7 1/2 56 15
17.97 0.707 56.45 2.22 P 1/2 7 3/4 - -
18.19 0.716 57.15 2.25 Q 8 57 16
18.35 0.722 57.65 2.27 Q 1/4 8 1/4 58 -
18.53 0.729 58.21 2.29 Q 3/4 8 1/2 - 17
18.61 0.733 58.47 2.30 R 8 5/8 59 -
18.69 0.736 58.72 2.31 R 1/4 8 3/4 - -
18.80 0.740 59.06 2.32 R 1/2 8 7/8 - -
18.89 0.748 59.34 2.35 R 3/4 9 - 18
19.10 0.752 60.00 2.36 S 9 1/8 60 -
19.22 0.757 60.38 2.38 S 1/4 9 1/4 - -
19.31 0.760 60.66 2.39 S 1/2 9 3/8 - -
19.41 0.764 60.98 2.40 S 3/4 9 1/2 - 19
19.51 0.768 61.29 2.41 T 9 5/8 61 -
19.62 0.772 61.64 2.43 T 1/4 9 3/4 - -
19.84 0.781 62.33 2.45 T 1/2 10 62 20
20.02 0.788 62.89 2.48 U 10 1/4 - 21
20.20 0.797 63.46 2.50 U 1/2 10 1/2 63 22
20.32 0.800 63.84 2.51 V 10 5/8 - -
20.44 0.805 64.21 2.53 V 1/4 10 3/4 64 -
20.68 0.814 64.97 2.56 V 1/2 11 - 23
20.76 0.817 65.22 2.57 W 11 1/8 65 -