Gear-Ratio MPH from RPM
Road speed (or RPM), wheel RPM, and tire revolutions per mile from engine RPM, transmission and axle ratios.
Example
You enter
- Solve for mph
- Engine RPM 2500
- Transmission gear ratio 1
- Axle ratio 3.55
- Tire diameter (in) 28.5
You get
- Road speed (MPH) 59.71
Details, formula, and sources
Road speed (or RPM), wheel RPM, and tire revolutions per mile from engine RPM, transmission and axle ratios, and tire diameter.
MPH = RPM * pi * dia(in) * 60 / (trans * axle * 63,360); inverse for RPM; revs/mile = 63,360 / (pi * dia).
Classical drivetrain kinematics; SAE J267 metric tire-size convention for decoding a tire code to diameter, by name.
Pure geometry, public; consistent with the tire-gearing tile.
Estimate. AHJ and licensed professional govern.
Field names used by the API: solve_for, rpm, trans_ratio, axle_ratio, tire_dia_in, mph
- No slip geometric speed ignores tire and torque-converter slipdrivetrain kinematics