Horsepower from Torque

This engine horsepower calculator applies the standard dynamometer equation: HP = torque (lb-ft) × RPM ÷ 5,252. At 5,252 RPM the two curves cross by definition — torque and horsepower are numerically equal there, which is why the constant appears in every dyno formula.

Crank vs Wheel Power

Manufacturers rate engines at the crankshaft, before the transmission and differential consume energy. This calculator estimates wheel horsepower by subtracting a drivetrain loss percentage typical for the layout — roughly 10–15% for RWD manuals and 15–20% for AWD or automatic cars.

Reading the Curve

With constant torque, horsepower rises linearly with RPM. Real engines have a torque peak and a falling torque curve at high RPM, so the true power curve peaks and drops — the shape tells you where the engine likes to run for maximum acceleration.