Enter Measurement
Formula used
The finger wrap measurement gives the inside circumference of the ring. We convert inches to millimeters and compute inside diameter as:
circumference_mm = inches × 25.4
diameter_mm = circumference_mm ÷ πTo estimate the US ring size, we use a standard reference chart of sizes versus inside circumference (mm). For in-between values we apply linear interpolation and then round to the user-selected step.
Note: Different manufacturers may vary slightly. Always verify with a physical ring sizer for the final fit.
Example data
Sample conversions you can try:
| Finger circumference (inches) | Circumference (mm) | Diameter (mm) | Nearest US size |
|---|---|---|---|
| 1.7500 | 44.45 | 14.15 | 3.00 |
| 1.8500 | 46.99 | 14.96 | 3.60 |
| 2.0000 | 50.80 | 16.17 | 5.08 |
| 2.1000 | 53.34 | 16.98 | 6.09 |
| 2.2000 | 55.88 | 17.79 | 7.07 |
| 2.3000 | 58.42 | 18.60 | 8.05 |
| 2.4000 | 60.96 | 19.40 | 9.06 |
| 2.5000 | 63.50 | 20.21 | 10.04 |
| 2.6000 | 66.04 | 21.02 | 11.05 |
| 2.7500 | 69.85 | 22.23 | 13.00 |
Reference chart (US size vs. circumference)
| US Size | Inside Circumference (mm) |
|---|---|
| 3 | 45.5 |
| 4 | 48 |
| 5 | 50.6 |
| 6 | 53.1 |
| 7 | 55.7 |
| 8 | 58.3 |
| 9 | 60.8 |
| 10 | 63.4 |
| 11 | 65.9 |
| 12 | 68.5 |
| 13 | 69.7 |