unit of measure
conversions equivalences

italiano misure english measure
Conversion table
Conversion factors in PDF

international ring size chart


UK
diameter
mm
circumference
mm
American
A
11.5
36.25
0.5
B
12.3
38.64
1
C
12.7
39.90
1.5
D
13.1
41.15
2
E
13.5
42.41
2.5
F
13.9
43.67
3
G
14.3
44.92
3.25
H
14.7
46.18
3.75
I
15.1
47.44
4.25
J
15.5
48.69
4.75
K
15.9
49.95
5.25
L
16.3
51.24
5.75
M
16.7
52.46
6.25
N
17.1
53.72
6.75
O
17.5
54.98
7
P
17.9
56.23
7.5
Q
18.3
57.49
8
R
18.7
58.75
8.5
S
19.1
60.00
9
T
19.5
61.26
9.5
U
19.9
62.52
10
V
20.3
63.77
10.5
W
20.7
65.00
11
X
21.1
66.29
11.5
Y
21.5
67.51
12
Z
21.9
68.77
12.5
Z+1
22.3
69.99
Z+2
22.7
71.31
Z+3
23.1
72.57
Z+4
23.5
73.83
Z+5
23.9
75.08
Z+6
24.3
76.34
Z+7
24.7
77.60
Z+8
25.1
78.86

To calculate:
American size= (diameter-11.54)/(0.83)
Japanese size= (diameter-12.67)*3
European size= circumference-40

USA
inches
mm
4
1.8307"
46.5
4 1/2
1.8818"
47.8
5
1.9291"
49.0
5 1/2
1.9803"
50.3
6
2.0275"
51.5
6 1/2
2.0787"
52.8
7
2.1259"
54.0
7 1/2
2.1771"
55.3
8
2.2283"
56.6
8 1/2
2.2755"
57.8
9
2.3267"
59.1
9 1/2
2.3740"
60.3
10
2.4251"
61.6
10 1/2
2.4724"
62.8
11
2.5236"
64.1
11 1/2
2.5708"
65.3
12
2.6220"
66.6
12 1/2
2.6732"
67.9
13
2.7204"
69.1

 
USA & Canada
diameter inches
Great Britain
France mm
Germany
Japan
Switzerland
000
0.390
---
---
---
---
---
00
0.422
---
---
---
---
---
0
0.454
---
---
---
---
---
1/2
0.462
A
---
---
---
---
3/4
0.471
A-1/2
---
---
---
---
1
0.487
B
---
---
1
---
1 1/4
0.495
B-1/2
---
---
---
---
1 1/2
0.503
C
---
---
---
---
1 3/4
0.511
C-1/2
---
---
---
---
2
0.520
D
41 1/2
13 1/4
2
1 1/2
2 1/4
0.528
D-1/2
42 1/8
13 1/2
---
---
2 1/2
0.536
E
42 3/4
13 3/4
3
2 3/4
2 3/4
0.544
E-1/2
43 3/8
---
---
3 3/8
3
0.553
F
44
14
4
4
3 1/4
0.561
F-1/2
44 5/8
14 1/4
---
4 5/8
3 1/2
0.569
G
45 1/4
14 1/2
5
5 1/4
3 3/4
0.577
G-1/2
45 7/8
14 3/4
6
5 7/8
4
0.586
H-1/2
46 1/2
15
7
6 1/2
4 1/4
0.594
I
47 1/8
15 1/4
---
7 1/8
4 1/2
0.602
I-1/2
47 3/4
15 1/2
8
7 3/4
4 3/4
0.610
J
48 3/8
---
---
8 3/8
5
0.619
J-1/2
49
15 3/4
9
9
5 1/4
0.627
K
49 5/8
16
---
9 5/8
5 1/2
0.635
K-1/2
50 1/4
16 1/4
10
10 1/4
5 3/4
0.643
L
50 7/8
---
11
10 7/8
6
0.652
L-1/2
51 1/2
16 1/2
12
11 1/2
6 1/4
0.660
M
52 1/8
16 3/4
---
12 1/8
6 1/2
0.668
M-1/2
52 3/4
17
13
12 3/4
6 3/4
0.676
N
53 3/8
---
---
13 3/8
7
0.685
O
54
17 1/4
14
14
7 1/4
0.693
O-1/2
54 5/8
17 1/2
---
14 5/8
7 1/2
0.701
P
55 1/4
17 3/4
15
15 1/4
7 3/4
0.709
P-1/2
55 7/8
---
---
15 7/8
8
0.717
Q
56 1/2
18
16
16 1/2
8 1/4
0.726
Q-1/2
57 1/8
18 1/4
---
17 1/8
8 1/2
0.734
R
57 3/4
18 1/2
17
17 3/4
8 3/4
0.742
R-1/2
58 3/8
18 3/4
---
18 3/8
9
0.750
S
59
19
18
19
9 1/4
0.759
S-1/2
59 5/8
19 1/4
---
19 5/8
9 1/2
0.767
---
60 1/4
19 1/2
19
20 1/4
9 3/4
0.775
T
60 7/8
19 3/4
---
20 7/8
10
0.783
T-1/2
61 1/2
20
20
21 1/2
10 1/4
0.792
U
62 1/8
20 1/4
21
22 1/8
10 1/2
0.800
U-1/2
62 3/4
20 1/2
22
22 3/4
10 3/4
0.808
V
63 3/8
---
---
23 3/8
11
0.816
V-1/2
64
20 3/4
23
24
11 1/4
0.825
W
64 5/8
---
---
24 5/8
11 1/2
0.833
W-1/2
65 1/4
21
24
25 1/4
11 3/4
0.841
X
65 7/8
---