Classic Muscle Car Top Speed from RPM
Estimate the top speed of a classic muscle car spinning 5,500 RPM in a 1:1 4th gear with 28-inch tires and a 3.55 rear axle.
How to use this tool
- Enter the engine RPM you want to evaluate.
- Enter the overall tire diameter in inches.
- Enter the transmission gear ratio for the selected gear and the axle ratio.
- The calculator returns vehicle speed in MPH.
Classic muscle cars with 4-speed manuals and big rear axle ratios have a wide RPM-to-speed range — calculate your top gear speed here.
Frequently asked questions
- How do you calculate vehicle speed from RPM?
- Speed (MPH) = RPM × tire circumference (in) ÷ (gear ratio × axle ratio × 1,056). The constant 1,056 converts inches/minute to MPH (63,360 in/mile ÷ 60 min/hr).
- Why does gear ratio matter for speed?
- A lower (numerically higher) gear ratio like 3.73 gives more torque but less top speed than a ratio like 2.73 at the same RPM.