Horsepower Calculator
Calculate horsepower, torque, and engine power specifications
Engine torque output
Engine speed
Mechanical Horsepower
SAE/Imperial
Kilowatts
127786 W
Torque
406.8 N⋅m
Metric Horsepower
DIN/Metric
Power Equivalents
How it works
Horsepower is a measure of how fast work is done. For engines it comes from torque and rotational speed; you can also estimate it from a vehicle's weight and how quickly it reaches a speed. The 5252 constant ties torque (lb-ft) and RPM to horsepower.
Horsepower
HP = (torque × RPM) ÷ 5252
- torque
- twisting force in lb-ft
- RPM
- revolutions per minute
Worked example
- Torque = 250 lb-ft
- At 6,000 RPM
- HP = (250 × 6000) ÷ 5252
≈ 286 horsepower.
Good to know
- One horsepower equals 550 foot-pounds per second, or about 746 watts.
- Horsepower and torque curves intersect at 5,252 RPM by definition.
- Peak horsepower usually occurs at higher RPM than peak torque.
Related Calculators
Frequently Asked Questions
How do I calculate horsepower from torque and RPM?
HP = (torque × RPM) ÷ 5252, with torque in lb-ft. An engine making 350 lb-ft at 4,500 RPM produces about 300 horsepower. Dynos actually measure torque and compute horsepower from it.
How do I convert horsepower to kilowatts?
One mechanical horsepower equals 0.7457 kW, so multiply hp by 0.7457 (or kW by 1.341 to go the other way). A 200 hp engine produces about 149 kW. Note that electric motors are usually rated directly in kilowatts.
What's the difference between horsepower and torque?
Torque is twisting force — what you feel pushing you into the seat — while horsepower is the rate of doing work: torque multiplied by how fast the engine spins. Two engines with equal torque differ in power if one sustains it at higher RPM.
What is metric horsepower (PS)?
Metric horsepower (PS, from the German Pferdestärke) is slightly smaller than imperial horsepower: 1 PS = 0.9863 hp. European manufacturers often quote PS, so a "300 PS" car has about 296 hp.
Why is wheel horsepower lower than advertised horsepower?
Manufacturers quote power at the crankshaft, but the transmission, driveshaft, and differential absorb some of it before it reaches the wheels. Typical drivetrain losses run about 10-15% for manual rear-wheel drive and 15-25% for automatics and all-wheel drive.