Quickly determine your vehicle's speed in miles per hour (MPH) from engine revolutions per minute (RPM). Our RPM to MPH calculator helps enthusiasts, tuners, and mechanics understand the relationship between engine speed, gearing, and tire size for optimal performance, fuel efficiency, and precise gear selection.
Formula:
MPH = (RPM × Tire Diameter) / (Final Drive Ratio × Transmission Ratio × 336)
Where:
- RPM: Engine Revolutions Per Minute
- Tire Diameter: Overall diameter of the tire in inches
- Final Drive Ratio: Differential or axle gear ratio (e.g., 3.73)
- Transmission Ratio: Gear ratio for the selected transmission gear (e.g., 1.00 for 4th gear direct drive)
- 336: A common automotive conversion constant (derived from 1056/π) to yield MPH when other units are in RPM and inches.