AUS & UK USA & Canada Europe Diameter (mm)  Circumference (mm)
E 2.25 42.5 13.5 42.4
E 1/2 2.5 43 13.7 43
F 2.75 43.5 14 43.6
F 1/2 3 44 14.1 44.2
G 3.25 45 14.4 44.8
G 1/2 3.5 45.4 14.5 45.5
H 3.75 46 14.8 46.1
H 1/2 4 47 15 46.8
I 4.25 47.5 15.2 47.4
I 1/2 4.5 48 15.4 48
J 4.75 48.5 15.6 48.7
J 1/2 5 49 15.8 49.3
K 5.25 50 16 50
K 1/2 5.5 50.5 16.2 50.6
L 5.75 51 16.4 51.2
L 1/2 6 52 16.6 51.9
M 6.25 52.5 16.8 52.5
M 1/2 6.5 53 17 53.1
N 6.75 53.5 17.2 53.8
N 1/2 7 54 17.4 54.4
O 7.25 55 17.6 55.1
O 1/2 7.5 55.5 17.8 55.7
P 7.75 56 18 56.3
P 1/2 8 57 18.2 57
Q 8.25 57.5 18.4 57.6
Q 1/2 8.5 58 18.6 58.3
R 8.75 59 18.8 58.9
R 1/2 9 59.9 19 59.5
S 9.25 60 19.2 60.2
S 1/2 9.5 61 19.4 60.8
T 9.75 61.5 19.6 61.4
T 1/2 10 62 19.8 62.1
U 10.25 62.5 20 62.7
U 1/2 10.5 63 20.2 63.4
V 10.75 64 20.4 64
V 1/2 11 64.5 20.6 64.6
W 11.25 65 20.8 65.3
W 1/2 11.5 66 21 65.9
X 11.75 66.5 21.2 66.6
X 1/2 12 67 21.4 67.2
Y 12.25 67.5 21.6 67.8
Z 12.75 68 22 68.5
Z 1/2 13 69 22.2 69.1