Horsepower Calculator

HP Converter: Type any value in any field and all other units update instantly. Useful for converting between horsepower, watts, kilowatts, BTU/hr, and metric horsepower (PS). The highlighted field is the one you last edited.

HP from Torque: Enter your engine's torque in pound-feet and the RPM at which that torque is measured. The calculator uses the standard automotive formula HP = Torque × RPM / 5252. To map a full power curve, try different RPM values from idle to redline.

Electrical to HP: Enter the voltage and current draw of an electric motor, plus its efficiency rating from the nameplate. The result shows input power, output horsepower, and how many watts are lost as heat. For three-phase motors, use the line-to-line voltage and one-phase current, then multiply the result by 1.732.

--- Unit Conversions ---
1 mechanical HP = 745.69987 watts
1 mechanical HP = 0.7457 kW
1 mechanical HP = 2,544.43 BTU/hr
1 mechanical HP = 550 ft-lb/s
1 mechanical HP = 1.01387 metric HP (PS)

--- Torque to HP ---
HP = Torque (lb-ft) × RPM / 5252

(5252 = 33,000 ft-lb/min ÷ 2π, derived from the definition
of 1 HP = 33,000 ft-lb per minute)

--- Electrical to Mechanical HP ---
Output HP = (Volts × Amps × Efficiency) / 745.7

--- Three-Phase Electric Motor ---
Output HP = (√3 × V × I × PF × Eff) / 745.7
(PF = power factor, typically 0.85-0.95)

Mechanical horsepower (the standard in the US) differs slightly from metric horsepower (PS, used in Europe and for some engine ratings). One metric HP is 735.5 watts vs. 745.7 watts for mechanical HP. Always clarify which standard you're using when comparing engine specs across markets.