Finding Your Size
The R09 comes in sizes 8 through 13. Since it's worn snugly — not loosely, like a fashion ring — getting the size right the first time makes all the difference for comfort and sensor accuracy.
Two easy ways to measure
- Use a ring you already own. Measure the inner diameter of a ring that fits your ring finger well and match it to the table below.
- Paper strip method. Wrap a thin strip of paper snugly around the base of your finger, mark where it overlaps, and measure the length in millimeters — that's your circumference. Match it to the table below.
| Size 8 | 18.2mm diameter · 57.2mm circumference |
| Size 9 | 19.0mm diameter · 59.5mm circumference |
| Size 10 | 19.8mm diameter · 62.1mm circumference |
| Size 11 | 20.6mm diameter · 64.6mm circumference |
| Size 12 | 21.4mm diameter · 67.2mm circumference |
| Size 13 | 22.2mm diameter · 69.7mm circumference |
A few tips
- Measure at the end of the day, when fingers are at their largest.
- If you're between sizes, size up slightly for comfort.
- Ordered the wrong size? It's covered under our standard 7-day return policy.