Engine RPM and Road Speed Calculator
Compare engine and wheel RPM or invert road speed with explicit tyre geometry and drive ratios.
A QUICK WALKTHROUGH
How to use this tool
- Select the model and explicitly enter each value and unit.
- Add named scenarios and any applicable user limits.
- Calculate, compare every row and copy or download the fixed report.
Equations and units
Wheel RPM = speed ÷ circumference × 60; engine RPM = wheel RPM × gear × final drive; circumference = π × diameter for diameter mode. Inverse speed = engine RPM ÷ gear ÷ final drive × circumference ÷ 60. 1 mph = 0.44704 m/s; 1 km/h = (1/3.6) m/s; 1 cm = 0.01 m; 1 mm = 0.001 m; 1 in = 0.0254 m; 1 ft = 0.3048 m.
Scope
Kinematics only. Unloaded diameter gives an approximate geometric circumference. No clutch or torque-converter slip, tyre fitment, shift or safety prediction.
Local processing
Inputs remain in this browser. Report numbers use full JavaScript floating-point precision; decimal inputs may round when parsed. No display rounding is applied.
GOOD TO KNOW
Common questions
Does this approve a vehicle operation?
No. This is arithmetic with user parameters and stated assumptions.