Horsepower Calculator
Calculate engine horsepower from torque and RPM using the classic 5252 formula.
Horsepower457.0hp
Kilowatts340.8kW
Metric horsepower (PS)463.3PS
Horsepower = torque (lb-ft) × engine speed (rpm) ÷ 5252. The constant 5252 comes from 33,000 ft-lb per minute (one horsepower) divided by 2π. At 400 lb-ft and 6,000 rpm: 400 × 6,000 ÷ 5252 ≈ 457.0 hp. Because of the 5252 constant, an engine's horsepower and torque curves always cross at exactly 5,252 rpm. 1 hp ≈ 0.7457 kW ≈ 1.014 metric PS.
Questions
How do I calculate horsepower from torque and RPM?
Multiply torque in pound-feet by engine RPM, then divide by 5252. An engine making 400 lb-ft at 6,000 rpm produces 400 × 6,000 ÷ 5252 ≈ 457 horsepower.
Why is the number 5252 used?
It converts the rotational power into horsepower: 33,000 ft-lb per minute (one horsepower) divided by 2π radians equals about 5252. It is also why torque and horsepower curves always meet at 5,252 rpm.