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Convert Sizes By Country
Diameter (mm)
diameter (inches)
circumference (mm)
circumference (inches)
British/Australian
19.41
9.91
0.39
31.13
A - 3
19.51
10.72
0.442
33.68
A - 2
19.62
11.53
0.454
36.22
A - 1
19.84
11.95
0.474
37.54
A
20.02
12.18
0.482
38.26
A 1/2
20.2
12.37
0.487
38.86
B
20.32
12.6
0.496
39.58
B 1/2
20.44
12.78
0.503
40.15
C
20.68
13
0.512
40.84
C 1/2
20.76
13.21
0.52
41.5
D
20.85
13.41
0.528
42.13
D 1/2
20.94
13.61
0.536
42.76
E
21.08
13.83
0.544
43.45
E 1/2
21.18
14.05
0.553
44.14
F
21.24
14.15
0.557
44.45
F 1/2
21.3
14.25
0.561
44.77
F 3/4
21.49
14.36
0.565
45.11
G
21.69
14.45
0.569
45.4
G 1/4
21.89
14.56
0.573
45.74
G 1/2
22.1
14.65
0.577
46.02
H
22.33
14.86
0.585
46.68
H 1/2
22.6
15.04
0.592
47.25
I
22.69
15.27
0.601
47.97
I 1/2
22.92
15.4
0.606
48.38
J
23.06
15.53
0.611
48.79
J 1/4
23.24
15.7
0.618
49.32
J 1/2
23.47
15.8
0.622
49.64
K
23.55
15.9
0.626
49.95
K 1/4
23.87
16
0.63
50.27
K 1/2
24.27
16.1
0.634
50.58
L
9.91
16.3
0.642
51.21
L 1/4
10.72
16.41
0.646
51.55
L 1/2
11.53
16.51
0.65
51.87
M
11.95
16.71
0.658
52.5
M 1/2
12.18
16.92
0.666
53.16
N
12.37
17.13
0.674
53.82
N 1/2
12.6
17.35
0.683
54.51
O
12.78
17.45
0.687
54.82
O 1/2
13
17.75
0.699
55.76
P
13.21
17.97
0.707
56.45
P 1/2
13.41
18.19
0.716
57.15
Q
13.61
18.35
0.722
57.65
Q 1/2
13.83
18.53
0.729
58.21
Q 3/4
14.05
18.61
0.733
58.47
R
14.15
18.69
0.736
58.72
R 1/4
14.25
18.8
0.74
59.06
R 1/2
14.36
18.89
0.748
59.34
R 3/4
14.45
19.1
0.752
60
S
14.56
19.22
0.757
60.38
S 1/4
14.65
19.31
0.76
60.66
S 1/2
14.86
19.41
0.764
60.98
S 3/4
15.04
19.51
0.768
61.29
T
15.27
19.62
0.772
61.64
T 1/4
15.4
19.84
0.781
62.33
T 1/2
15.53
20.02
0.788
62.89
U
15.7
20.2
0.797
63.46
U 1/2
15.8
20.32
0.8
63.84
V
15.9
20.44
0.805
64.21
V 1/4
16
20.68
0.814
64.97
V 1/2
16.1
20.76
0.817
65.22
W
16.3
20.85
0.821
65.5
W 1/4
16.41
20.94
0.824
65.78
W 1/2
16.51
21.08
0.83
66.22
W 3/4
16.71
21.18
0.834
66.54
X
16.92
21.24
0.836
66.73
X 1/4
17.13
21.3
0.839
66.92
X 1/2
17.35
21.49
0.846
67.51
Y
17.45
21.69
0.854
68.14
Y 1/2
17.75
21.89
0.862
68.77
Z
17.97
22.1
0.87
69.43
Z +1/2
18.19
22.33
0.879
70.15
Z+1
18.35
22.6
0.89
71
Z+1.5
18.53
22.69
0.893
71.28
Z+2
18.61
22.92
0.902
72
Z+2.5
18.69
23.06
0.908
72.45
Z+3
18.8
23.24
0.915
73.01
Z+3.5
18.89
23.47
0.924
73.73
Z+4
19.1
23.55
0.927
73.98
Z+4.5
19.22
23.87
0.94
74.99
Z+5
19.31
24.27
0.956
76.25
Z+6
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