Gear Ratio Calculator
Estimate MPH by gear, final-drive multiplication and cruising RPM from transmission ratios, axle ratio, tire diameter and engine RPM.
| Gear | Ratio | MPH |
|---|
Hit Calculate to see gear speeds
Calculate to classify cruise gearing
Metrics appear after calculation
Your explanation appears here
MPH = RPM × tire diameter ÷ (gear ratio × axle ratio × 336). Cruise RPM uses the inverse formula.
Your plan appears after calculation
Test a different axle ratio, tire height or RPM without changing your main result.
Calculate your baseline first
It uses MPH = RPM × tire diameter ÷ (gear ratio × axle ratio × 336). The 336 factor converts tire diameter in inches and engine RPM into miles per hour.
A numerically lower axle ratio, such as 3.08 instead of 4.10, lowers engine RPM at the same speed. A taller tire also lowers cruise RPM.
Tire height changes how far the vehicle travels per wheel revolution. A larger tire diameter increases MPH at the same RPM, while a smaller tire does the opposite.
Results are estimates generated locally in your browser using standard gear-ratio formulas. Actual speed and RPM can vary with torque converter slip, tire growth, clutch slip, tread wear, calibration and drivetrain losses. Use this calculator for planning and comparison only; verify safety-critical gearing with a qualified mechanic or drivetrain specialist.
