Horsepower & Torque Calculator
Calculate horsepower from torque and engine RPM, or calculate torque from horsepower and RPM, using the standard relationship for horsepower and pound-feet.
Calculator
Input definitions
- Torque: twisting force expressed in pound-feet (lb-ft).
- RPM: rotational speed in revolutions per minute.
- Horsepower: the rate of doing work calculated from torque and rotational speed.
The 5252 constant applies to the horsepower/lb-ft relationship used here. Different power or torque units require the appropriate conversion or constant.
Worked example
At 4,000 RPM and 400 lb-ft:
HP = 400 × 4000 ÷ 5252 ≈ 304.6 hp
At 5,252 RPM, equal numerical values of torque in lb-ft and horsepower intersect because of the unit relationship represented by the 5252 constant.
Engineering notes
This is a mathematical relationship between torque, rotational speed and horsepower. It does not estimate engine efficiency or predict a complete torque curve. If torque or horsepower comes from a dyno, be clear whether the measurement is at the engine or at the wheels because drivetrain losses and test conditions affect measured values.