Vehicle Speed Calculator

Inputs

Engine speed (n_e)

Crankshaft speed.

rpm

Tire diameter (D)

Rolling tire diameter. Use measured rolling diameter for precision.

Transmission ratio (G)

Selected gear ratio. Overdrive gears are less than 1.0.

Final drive ratio (F)

Axle or differential ratio.

Transfer ratio (T)

Transfer-case or auxiliary ratio. Use 1.0 if none.

Default result

Vehicle speed(v)

111.2km/h

Pass

Also computed

Wheel speed(n_w)893.7rpm

Overall ratio2.797

Tire circumference2,075mm

Method notes 2 notes

Assumes no clutch slip, torque-converter slip, tire growth or rolling-radius change under load.
Use manufacturer revs-per-mile data when speedometer calibration matters.