Horsepower Calculator
Calculate horsepower or kilowatts from torque and RPM
This is engine power from a torque figure and an engine speed. It is not a unit converter and it is not a chassis-dyno reading. To change horsepower into watts or BTU per hour, use the power converter.
Calculator Inputs
Pound-feet, or newton-meters if you chose metric
Results
Enter values above to see your results
How to use this calculator
- Choose pound-feet or newton-meters.
- Enter torque and the RPM at which that torque applies.
- Read horsepower, or kilowatts if you chose metric.
How the calculation works
Mechanical horsepower is torque in pound-feet × RPM ÷ 5,252. The 5,252 comes from 33,000 foot-pounds per minute divided by 2π.
In metric units, kilowatts are torque in newton-meters × RPM ÷ 9,550. The 9,550 is the usual rounded form of the exact constant, which is about 9,549.
What this number is
The result is power at the torque and speed you entered. Wheel horsepower is lower because of losses through the drivetrain. This page does not apply a drivetrain factor.
Worked example
300 lb·ft at 3,000 RPM
300 × 3,000 ÷ 5,252= 171.36 hpTips & Best Practices
- •Use the torque at that RPM, not a peak torque from a different speed.
- •5,252 is exact for this definition of horsepower. 9,550 is rounded.
Frequently Asked Questions
How do you calculate horsepower from torque?
Multiply torque in pound-feet by RPM and divide by 5,252. Three hundred pound-feet at 3,000 RPM is 171.36 horsepower.
What is the metric formula?
Multiply torque in newton-meters by RPM and divide by 9,550. The result is kilowatts.
Is this wheel horsepower?
No. It is power from the torque and RPM you typed. A dyno at the wheels reads less, and this page does not guess that loss.