US / Canada to Swiss / IT / ES ring size
The short answer
By the formula, US / Canada 8 is Swiss / IT / ES 17.
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 | Swiss / IT / ES |
|---|---|
| 3 | 4 |
| 3.5 | 5 |
| 4 | 7 |
| 4.5 | 8 |
| 5 | 9 |
| 5.5 | 11 |
| 6 | 12 |
| 6.5 | 13 |
| 7 | 14 |
| 7.5 | 16 |
| 8 | 17 |
| 8.5 | 18 |
| 9 | 19 |
| 9.5 | 21 |
| 10 | 22 |
| 10.5 | 23 |
| 11 | 25 |
| 11.5 | 26 |
| 12 | 27 |
| 12.5 | 28 |
| 13 | 30 |