Horsepower Calculator
Calculate mechanical horsepower from torque and RPM, convert between HP, kW, and PS, or compute power from force and velocity for engines and motors.
Related Calculators
You might also find these calculators useful
Calculate Engine & Motor Power
Horsepower (HP) is the standard unit for measuring engine and motor power output. Our calculator helps you compute horsepower from torque and RPM, calculate power from force and velocity, or convert instantly between HP, kW, PS (metric horsepower) and watts for any mechanical system.
What is Horsepower?
Horsepower was developed by James Watt to compare steam engine power to draft horses. One mechanical horsepower equals 550 foot-pounds per second or 33,000 foot-pounds per minute. Today, different horsepower standards exist including Imperial (HP), Metric (PS/CV), and Electrical (exactly 746W).
Horsepower from Torque
HP = (Torque × RPM) / 5252How to Use the Calculator
Select calculation mode: Torque & RPM, Power Conversion, or Force & Velocity.
For torque mode, enter torque value and engine RPM.
For power conversion, enter power in any unit (HP, PS, kW, Watts).
For force mode, enter force and velocity with appropriate units.
View results in multiple power units simultaneously.
Common Applications
Automotive Tuning
Calculate engine horsepower from dyno torque readings.
Electric Vehicles
Convert motor kW ratings to equivalent horsepower.
Industrial Equipment
Size motors for conveyors, pumps, and manufacturing machinery.
Marine Engines
Compare boat engine power ratings across manufacturers.
Why Calculate Horsepower?
Engine Performance
Understand your vehicle's power output at different RPM ranges.
Motor Selection
Size motors correctly for pumps, compressors, and machinery.
Power Comparison
Compare specifications across different measurement systems.
Convert EV & Motor Power
Translate electric-motor kW ratings into equivalent HP and PS.
Compare Global Specs
Reconcile HP, PS/CV and kW figures across US, European and metric spec sheets.
Frequently Asked Questions
The constant 5252 comes from (33,000 ft·lb/min) ÷ (2π rad/rev). Since HP = 33,000 ft·lb/min and torque is measured in lb·ft with RPM in revolutions per minute, this constant converts the units correctly.
Imperial Horsepower (HP) equals 745.7 watts and is based on 550 ft·lb/s. Metric Horsepower (PS/CV/pk) equals 735.5 watts and is based on 75 kgf·m/s. PS is about 1.4% less than HP.
Divide kilowatts by 0.7457 to get Imperial HP, or divide by 0.7355 to get Metric HP (PS). For example, 100 kW ≈ 134 HP ≈ 136 PS.
Brake horsepower is power measured at the engine crankshaft, before transmission losses. Wheel horsepower (WHP) is lower due to drivetrain friction, typically 15-20% less than BHP.
Multiply Imperial horsepower by 0.7457 to get kilowatts (multiply metric PS by 0.7355). For example, 150 HP × 0.7457 ≈ 111.9 kW. To go the other way, divide kW by 0.7457.