Ring sizes follow the US scale. Measure an existing ring’s inner diameter, or wrap a strip of paper around the finger and measure the length in millimetres.
| US size | Diameter (mm) | Circumference (mm) |
|---|---|---|
| 7 | 17.3 | 54.4 |
| 8 | 18.1 | 57.0 |
| 9 | 19.0 | 59.5 |
| 10 | 19.8 | 62.1 |
| 11 | 20.6 | 64.6 |
| 12 | 21.4 | 67.2 |
