Table of international equivalences for rings sizes


France

USA / Canada

United Kingdom

Japan

Switzerland
Inner
diameter
(mm)
Inner
diameter
(Inches)
Inner
circumference
(Inches)
48
4 1/2
8
 
15.3
0.602
1.89
48.7
4 3/4
J
 
9
15.5
0.61
1.915
49.3
5
J 1/2
9
 
15.7
0.618
1.941
49.9
5 1/4
K
 
10
15.9
0.626
1.966
50.6
5 1/2
K 1/2
10
 
16.1
0.634
1.991
51.2
5 3/4
L
 
11.75
16.3
0.642
2.016
51.8
6
L 1/2
11
12.75
16.5
0.65
2.041
52.5
6 1/4
12
 
16.7
0.658
2.066
53.1
6 1/2
M 1/2
13
14
16.9
0.666
2.091
53.8
6 3/4
N
 
 
17.1
0.674
2.116
54.4
7
N 1/2
14
15.25
17.3
0.682
2.141
55
7 1/4
 
 
17.5
0.69
2.167
55.7
7 1/2
O 1/2
15
16.5
17.7
0.698
2.192
56.3
7 3/4
 
 
17.9
0.706
2.217
56.9
8
P 1/2
16
17.75
18.1
0.714
2.242
57.6
8 1/4
 
 
18.3
0.722
2.267
58.2
8 1/2
Q 1/2
17
 
18.5
0.73
2.292
58.9
8 3/4
R
 
19
18.7
0.738
2.317
59.5
9
R 1/2
18
 
18.9
0.746
2.342
60.1
9 1/4
S
 
20.25
19.2
0.754
2.368
60.8
9 1/2
S 1/2
19
 
19.4
0.762
2.393
61.4
9 3/4
T
 
21.5
19.6
0.770
2.418
62.1
10
T 1/2
20
 
19.8
0.778
2.443
62.7
10 1/4
U
21
 
20.0
0.786
2.468
63.3
10 1/2
U 1/2
22
22.75
20.2
0.794
2.493
64.0
10 3/4
V
 
 
20.4
0.802
2.518
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