US / Canada to EU / ISO ring size
The short answer
By the formula, US / Canada 8 is EU / ISO 57.
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 | EU / ISO |
|---|---|
| 3 | 44 |
| 3.5 | 45 |
| 4 | 47 |
| 4.5 | 48 |
| 5 | 49 |
| 5.5 | 51 |
| 6 | 52 |
| 6.5 | 53 |
| 7 | 54 |
| 7.5 | 56 |
| 8 | 57 |
| 8.5 | 58 |
| 9 | 59 |
| 9.5 | 61 |
| 10 | 62 |
| 10.5 | 63 |
| 11 | 65 |
| 11.5 | 66 |
| 12 | 67 |
| 12.5 | 68 |
| 13 | 70 |