RPM vs Speed Calculator

Estimate road speed from RPM, gearing, and tyre diameter.

Calculate Vehicle Speed

Calculation mode:

Engine RPM:

Vehicle speed:

Speed unit:

Gear ratio:

Additional gear ratios (optional):

Final drive ratio:

Tyre diameter (inches):

Need diameter? Use the tyre size calculator to convert size to inches. Add extra ratios to compare multiple gears.

How the Math Works

We calculate tyre circumference, then divide by total gearing (gear ratio times final drive). The constant 1056 converts inches per minute into miles per hour.

Higher gearing: More RPM for the same speed.
Larger tyres: More speed at the same RPM.
Real-world factors: Converter slip and tyre growth can change results.