Power from Torque & RPM

This formula converts how hard an engine is twisting the crankshaft (torque) and how fast it is spinning (rpm) into output power. It comes from the rotational power relationship P = torque × angular speed, with the rpm value converted into radians per second and the result expressed in kilowatts, which is why the constant 9549 appears. In practice, higher torque or higher engine speed both increase power, but only if the engine can maintain that torque at that speed.

Use this when you know an engine’s torque at a particular rpm and want to estimate its power output in kilowatts. It is common in automotive engineering, dyno testing, and comparing engine performance across different speed ranges.

• Using torque values in lb·ft without converting them to N·m first
• Putting the rpm value into the formula without using the constant 9549 or an equivalent unit conversion
• Assuming more rpm always means more power, even when torque drops sharply