Reference chart for ring size conversions
US  Size
Dia.in inch
Dia. in MM
British 
French 
German 
Japanese 
Swiss 
0000
.390
9.91
-
       
00
.422
10.72
-
       
0
.454
11.53
-
       
1/2
.474
11.95
A
       
3/4
.482
12.18
A 1/2
       
1
.487
12.37
B
   
1
 
1 1/4
-
12.60
B 1/2
       
1 1/2
.503
12.78
C
       
1 3/4
-
13.00
C 1/2
       
2
.520
13.21
D
41 1/2
13 1/2
2
1 1/2
2 1/4
-
13.41
D 1/2
-
-
   
2 1/2
.536
13.61
E
42 3/4
13 3/4
3
2 3/4
2 3/4
-
13.83
E 1/2
-
-
   
3
.553
14.05
F
44
14
4
4
3 1/8
-
14.15
F 1/2
-
-
   
3 1/4
-
14.25
-
-
-
   
3 3/8
-
14.36
G
45 1/4
-
5
5 1/4
3 1/2
.569
14.45
-
-
14 1/2
   
3 5/8
-
14.56
 G 1/2
-
 
6
 
3 3/4
-
14.65
H
46 1/2
   
6 1/2
4
.585
14.86
H 1/2
-
15
7
 
4 1/4
-
15.04
47 3/4
   
7 3/4
4 1/2
.601
15.27
I 1/2
-
15 1/4
8
 
4 5/8
-
15.40
J
49
15 1/2
 
9
4 3/4
-
15.53
-
-
     
5
.618
15.70
J 1/2
-
15 3/4
9
 
5 1/8
-
15.80
K
50
   
10
5 1/4
-
15.90
-
-
     
5 3/8
-
16.0
K 1/2
-
 
10
 
5 1/2
.634
16.10
L
51 3/4
16
 
11 3/4
5 3/4
-
16.30
-
-
     
5 7/8
-
16.41
L 1/2
-
     
6
.650
16.51
M
52 3/4
16 1/2
12
12 3/4
6 1/4
-
16.71
M 1/2
-
     
6 1/2
.666
16.92
N
54
17
13
14
6 3/4
-
17.13
N 1/2
-
     
7
.683
17.35
O
55 1/4
17 1/4
14
15 1/4
7 1/4
-
17.45
O 1/2
-
     
7 1/2
.699
17.75
P
56 1/2
17 3/4
15
16 1/2
7 3/4
-
17.97
P 1/2
-
     
8
.716
18.19
Q
57 3/4
18
16
17 3/4
8 1/4
-
18.35
Q 1/2
-
     
8 1/2
.732
18.53
-
-
18 1/2
17
 
8 5/8
-
18.61
R
59
   
19
8 3/4
-
18.69
-
-
     
8 7/8
-
18.80
R 1/2
-
     
9
.748
18.89
-
-
19
18
 
9 1/8
-
19.10
S
60 1/4
   
20 1/4
9 1/4
-
19.22
-
-
     
9 3/8
-
19.31
S 1/2
-
     
9 1/2
.764
19.41
-
-
19 1/2
19
 
9 5/8
-
19.51
T
61 1/2
   
21 1/2
9 3/4
-
19.62
-
-
     
10
.781
19.84
T 1/2
-
20
20
 
10 1/4
-
20.02
U
62 3/4
 
21
22 3/4
10 1/2
.797
20.20
U 1/2
-
20 1/4
22
 
10 5/8
-
20.32
V
63
   
23 3/4
10 3/4
-
20.44
-
-
     
11
.814
20.68
V 1/2
-
20 3/4
23
 
11 1/8
-
20.76
W
65
   
25
11 1/4
-
20.85
-
-
     
11 3/8
-
20.94
W 1/2
-
     
11 1/2
-
21.08
-
-
21
24
 
11 5/8
.830
21.18
X
66 1/4
   
26 1/4
11 3/4
-
21.24
-
-
     
11 7/8
-
21.30
X 1/2
-
     
12
.846
21.49
Y
67 1/2
21 1/4
25
27 1/2
12 1/4
-
21.69
Y 1/2
-
     
12 1/2
.862
21.89
Z
68 3/4
21 3/4
26
28 3/4
12 3/4
-
22.10
Z 1/2
-
     
13
.879
22.33
-
-
22
27
 
This is a useful guide, however we are not responsible for your result.