US / Canada to UK / AU ring size
The short answer
By the formula, US / Canada 8 is UK / AU P 1/2.
Inner circumference 56.9 mm. Ring sizes are defined by that one measurement, so this conversion is exact up to rounding: US sizes are rounded to the nearest quarter, UK letters to the nearest half.
| US / Canada | UK / AU |
|---|---|
| 3 | F 1/2 |
| 3.5 | G 1/2 |
| 4 | H 1/2 |
| 4.5 | I 1/2 |
| 5 | J 1/2 |
| 5.5 | K 1/2 |
| 6 | L 1/2 |
| 6.5 | M 1/2 |
| 7 | N 1/2 |
| 7.5 | O 1/2 |
| 8 | P 1/2 |
| 8.5 | Q 1/2 |
| 9 | R 1/2 |
| 9.5 | S 1/2 |
| 10 | T 1/2 |
| 10.5 | U 1/2 |
| 11 | V 1/2 |
| 11.5 | W 1/2 |
| 12 | X 1/2 |
| 12.5 | Y 1/2 |
| 13 | Z 1/2 |