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International Ring Size Conversion Chart

Circumference (mm)
Europe / ISO
Diameter (mm) USA / Canada UK / Australia Asia Switzerland
44.2 14.1 3 F 4 4
44.8 14.3
F-1/2 5 5-1/4
45.5 14.5 3-1/2 G

46.1 14.7
G-1/2 6 6-1/2
46.8 14.9 4 H 7
47.4 15.1
H-1/2
7-3/4
48.0 15.3 4-1/2 I 8
48.7 15.5
J
9
49.3 15.7 5 J-1/2 9
50.0 15.9
K
10
50.6 16.1 5-1/2 K-1/2 10
51.2 16.3
L
11-3/4
51.9 16.5 6 L-1/2 11 12-3/4
52.5 16.7
M 12
53.1 16.9 6-1/2 M-1/2 13 14
53.8 17.1
N

54.4 17.3 7 N-1/2 14 15-1/4
55.1 17.5
O

55.7 17.7 7-1/2 O-1/2 15 16-1/2
56.3 17.9
P

57.0 18.1 8 P-1/2 16 17-3/4
57.6 18.3
Q

58.3 18.5 8-1/2 Q-1/2 17
58.9 18.8
R
19
59.5 19.0 9 R-1/2 18
60.2 19.2
S
20-1/4
60.8 19.4 9-1/2 S-1/2 19
61.4 19.6
T
21-1/2
62.1 19.8 10 T-1/2 20
62.7 20.0
U 21
63.4 20.2 10-1/2 U-1/2 22 22-3/4
64.0 20.4
V

64.6 20.6 11 V-1/2 23
65.3 20.8
W
25
65.9 21.0 11-1/2 W-1/2 24
66.6 21.2
X

67.2 21.4 12 X-1/2 25 27-1/2
67.8 21.6
Y

68.5 21.8 12-1/2 Z 26 28-3/4
69.1 22.0
Z-1/2

69.7 22.2 13
27
70.4 22.4
Z + 1

71.0 22.6 13-1/2