Gear Ratio & RPM Calculator
Calculate engine RPM at a given speed for any combination of gear ratio, final drive ratio, and tire size. Useful for selecting gears and rear-end ratios.
Results
Visualization
How It Works
Engine RPM = (Speed x Gear Ratio x Final Drive x 336) / Tire Diameter. Lower highway RPM means better fuel economy and less engine wear; higher RPM means quicker acceleration response. A numerically higher final drive (e.g., 4.10 vs 3.23) gives more acceleration but higher cruise RPM. Overdrive gears (ratio below 1.0) reduce cruise RPM. Taller tires have the same effect as a lower numerical axle ratio.