Size Guide
Find your perfect fit.
Smart Ring comes in 6 sizes. The right fit means accurate readings, all-day comfort, and a ring that stays put. Choose your sizing method below.
Three ways to measure.
Pick whichever is easiest. All three work.
1
Print our ring sizer
Download our free printable sizer. Print at 100% scale, then slide your finger through each circle to find the perfect fit. Most accurate method without ordering a kit.
Download PDF Ring Sizer2
Paper or string method
Wrap a thin strip of paper or string around the base of your finger. Mark where it overlaps, then measure the length in millimeters with a ruler. Match your measurement to the chart below.
3
Ring Sizer app
Download a free Ring Sizer app on iPhone or Android. Place your finger on the screen or use an existing ring you already own to find your size in seconds.
Ring size chart
Match your finger measurement to the right size.
| Size | Inner diameter | Circumference |
|---|---|---|
| No.7 | 17.3 mm | 54.4 mm |
| No.8 | 18.3 mm | 57.5 mm |
| No.9 | 19.1 mm | 60.0 mm |
| No.10 | 20.0 mm | 62.8 mm |
| No.11 | 20.8 mm | 65.4 mm |
| No.12 | 21.6 mm | 67.8 mm |
Tips for the perfect fit
- Measure at the end of the day. Fingers swell slightly throughout the day, so this gives the most reliable reading.
- Avoid extreme temperatures. Cold shrinks fingers, heat expands them. Measure at room temperature.
- Measure three times. Take the average for best accuracy.
- Between sizes? Size up. A slightly loose ring is better than one that feels tight.
- Sensor placement matters. The ring should sit snug enough that the sensors stay in contact with your skin, but loose enough to slide off without force.