Gear Ratio Calculator

Calculate final drive ratio and speed at RPM from gear and axle ratios.

Higher number = lower gear (more torque multiplication)
Common ratios: 2.73, 3.08, 3.23, 3.55, 3.73, 4.10
Leave at 1.0 for 2WD or high range

Common Gear Ratios

GearTypical AutoManual
1st2.973.42
2nd1.622.14
3rd1.001.36
4th0.681.00
5th-0.82
6th-0.63

Understanding Gear Ratios

Final Drive Ratio

Final Drive = Transmission Ratio × Differential Ratio × Transfer Case Ratio

Speed Calculation

Speed (MPH) = (RPM × Tire Diameter × π) / (Final Drive × 336)

A higher final drive ratio provides more torque but lower top speed in that gear.