Horsepower Calculator
Calculate engine horsepower from torque and RPM, or work backward to find torque or RPM from a known HP figure. This calculator uses the standard mechanical horsepower formula and includes a kilowatt conversion for international comparisons.
The fundamental relationship between horsepower, torque, and RPM is: HP = (Torque in lb-ft x RPM) / 5252. The constant 5252 comes from the definition of one horsepower (33,000 ft-lbs of work per minute) divided by 2π. At exactly 5,252 RPM, horsepower and torque are equal.
This formula applies to mechanical (brake) horsepower as measured at the crankshaft or wheels. Wheel horsepower is typically 15-20% less than crank horsepower due to drivetrain losses. Dynamometer (dyno) results usually report both.
The kilowatt conversion (1 HP = 0.7457 kW) is used in most countries outside the US. Electric vehicles are commonly rated in kW, while combustion engines in the US market still use horsepower.