This is a chart that will be extremely helpful for you to determine the ring size that you need. You can either make use of a tape or a small piece of string to measure the area that will be occupied by the ring. When it becomes a complete circle, make a mark on such string. This will be helpful for you to compare with the chart that is mentioned below.
Inside Diameter
Inside Circumference
SIZE
MM
MM
US / CA
UK / AU/ SAF
FR / DE
Europe
14.1
44.2
3
F
44
4.25
14.5
45.5
3.5
G
45.5
5.5
14.9
46.8
4
H
47
6.75
15.3
48
4.5
I
48
8
15.7
49.3
5
J-½
50
9.25
16.1
50.6
5.5
K-½
51
10.5
16.5
51.9
6
L-½
52
11.75
16.9
53.1
6.5
M-½
53
13.25
17.3
54.4
7
N-½
54
14.5
17.7
55.7
7.5
O-½
56
15.75
18.1
57
8
P-½
57
17
18.5
58.3
8.5
Q-½
58
18.25
19
59.5
9
R-½
59
19.5
19.4
60.8
9.5
S-½
61
20.75
19.8
62.1
10
T-½
62
22
20.2
63.4
10.5
U-½
63
23.25
20.6
64.6
11
V-½
64
24.75
21
65.9
11.5
W-½
66
26
21.4
67.2
12
X-½
67
27.25
21.8
68.5
12.5
Z
68
28.5
22.2
69.7
13
Z+1
70
29.75
22.6
71
13.5
Z+1.5
71
31
23
72.3
14
Z+2
72
32.25
23.4
73.5
14.5
Z+2.5
73.5
33.5
23.8
74.8
15
Z+3
75
34.75
OTHER TIPS
1)*Measure your finger in warm temperatures at the end of the day.
2)*If your knuckle is a lot larger than the base of your finger,measure both the base of your finger and your knuckle and select a size between the two.
3)*When considering a wide band, move up a size from your measurement, for comfort’s sake.