Calculate mechanical horsepower from torque and RPM, convert between HP, kW, and PS, or compute power from force and velocity for engines and motors.
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Horsepower (HP) is the standard unit for measuring engine and motor power output. Our calculator helps you compute horsepower from torque and RPM, convert between power units, or calculate power from force and velocity for any mechanical system.
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
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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.