Speedometer Calibration Calculator
Calculate speedometer error from tire size or gear ratio changes and find your actual speed.
Quick Reference
| Diameter Change | Error | @60 mph shows |
|---|---|---|
| +1 inch | ~3.5% | 57.9 mph actual |
| +2 inches | ~7% | 55.8 mph actual |
| +3 inches | ~10.5% | 53.7 mph actual |
| -1 inch | ~3.5% | 62.2 mph actual |
*Larger tires = speedometer reads SLOW (actual speed higher)