Convert between horsepower, torque, and RPM using the standard formula
Our Horsepower Calculator uses the standard engineering formula to convert between horsepower, torque, and RPM. Enter any two values to find the third. Results are shown in both horsepower (HP) and kilowatts (kW).
The relationship between horsepower and torque is fundamental to understanding engine performance. Horsepower measures the rate at which work is done, while torque measures rotational force.
The constant 5252 comes from the conversion of rotational speed (RPM) and torque (ft-lb) into horsepower. At exactly 5252 RPM, torque and horsepower values are always equal because RPM/5252 = 1. This is why the HP and torque curves always cross at 5252 RPM on a dyno chart.
Horsepower (HP) is the imperial unit of power, commonly used in the US and UK. Kilowatts (kW) are the SI (metric) unit of power. 1 HP equals approximately 0.7457 kW. Most countries outside the US use kW for engine power ratings.