Not sure of your size? Use our complete ring size guide to measure at home and convert between international standards.
| Inner Circumference (mm) |
Inner Diameter (mm) |
India |
U.S.A. & Canada |
U.K. / Australia / Ireland |
Europe (ISO) |
Japan / China |
| 48 |
15.27 |
8 |
4 1/2 |
I |
48 |
8 |
| 49 |
15.70 |
9 |
5 |
J 1/2 |
49 |
9 |
| 51 |
16.10 |
11 |
5 1/2 |
K 1/2 |
51 |
10 |
| 52 |
16.51 |
12 |
6 |
L 1/2 |
52 |
11 |
| 53 |
16.92 |
13 |
6 1/2 |
M 1/2 |
53 |
13 |
| 55 |
17.35 |
14 |
7 |
N 1/2 |
55 |
14 |
| 56 |
17.75 |
15 |
7 1/2 |
O 1/2 |
56 |
15 |
| 57 |
18.19 |
16 |
8 |
P 1/2 |
57 |
16 |
| 58 |
18.53 |
17 |
8 1/2 |
Q 1/2 |
58 |
17 |
| 59 |
18.89 |
18 |
9 |
R 1/2 |
59 |
18 |
| 61 |
19.41 |
19 |
9 1/2 |
S 1/2 |
61 |
19 |
| 62 |
19.84 |
20 |
10 |
T 1/2 |
62 |
20 |
| 63 |
20.20 |
22 |
10 1/2 |
U 1/2 |
63 |
22 |
| 65 |
20.68 |
23 |
11 |
V 1/2 |
65 |
23 |
| 66 |
21.08 |
24 |
11 1/2 |
W 1/2 |
66 |
24 |
| 68 |
21.49 |
25 |
12 |
X 1/2 |
68 |
25 |
| 69 |
21.89 |
26 |
12 1/2 |
Z |
69 |
26 |
| 70 |
22.33 |
27 |
13 |
Z 1/2 |
70 |
27 |
India is highlighted as our default standard. U.S.A. & Canada share a system, as do the U.K., Australia & Ireland, and Japan & China. The Europe (ISO) size equals the inner circumference in millimetres — which is why those two columns match.
