Gear Ratio Calculator

Calculate a top speed at a given engine speed at different transmission gearing. You may find it useful for calculating theoretical top speeds in mile and half mile racing such as the Texas Mile.



  • Engine RPM - engine RPM that you will be shifting at or your cruising engine speed
  • Rear Diff Ratio - gearing ratio of your rear differential
  • Tire Height (in.) - tire height in inches


Engine RPM Rear Diff Ratio Tire Height (in.)

  Gear Ratio MPH
1st Gear
2nd Gear
3rd Gear
4th Gear
5th Gear
6th Gear