Swiss / IT / ES to US / Canada ring size
The short answer
By the formula, Swiss / IT / ES 17 is US / Canada 8.
Inner circumference 57 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.
| Swiss / IT / ES | US / Canada |
|---|---|
| 4 | 3 |
| 5 | 3.25 |
| 6 | 3.75 |
| 7 | 4 |
| 8 | 4.5 |
| 9 | 5 |
| 10 | 5.25 |
| 11 | 5.75 |
| 12 | 6 |
| 13 | 6.5 |
| 14 | 6.75 |
| 15 | 7.25 |
| 16 | 7.75 |
| 17 | 8 |
| 18 | 8.5 |
| 19 | 8.75 |
| 20 | 9.25 |
| 21 | 9.5 |
| 22 | 10 |
| 23 | 10.5 |
| 24 | 10.75 |
| 25 | 11.25 |
| 26 | 11.5 |
| 27 | 12 |
| 28 | 12.25 |
| 29 | 12.75 |
| 30 | 13.25 |