Horsepower from torque and rpm
Power is torque times rotational speed. Enter the torque at a given rpm to get the power at that point.
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How to use it
- Enter torque, torque unit and engine speed.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Power (W) = torque (N·m) × rpm × 2π ÷ 60. Mechanical hp = W ÷ 745.7; metric PS = W ÷ 735.5. In lb-ft: hp = torque × rpm ÷ 5252.
Example
Inputs: Torque = 400, Torque unit = N·m, Engine speed = 4,000 rpm. Result: Horsepower: 224.7 hp; Kilowatts: 167.6 kW; Metric horsepower: 227.8 PS.
Limits and caveats
- The result is power at the rpm you entered only; peak power usually comes at higher rpm than peak torque.
- Factory figures are at the crank; wheel power is lower because of drivetrain losses.
Questions about this tool
Why do hp and torque curves cross at 5252 rpm?
Because hp = lb-ft × rpm ÷ 5252, the two numbers are equal at 5252 rpm when plotted in those units.
What is the difference between hp and PS?
Mechanical hp is 745.7 W and metric PS is 735.5 W, so the PS figure is about 1.4% higher.
Can I combine peak torque with redline rpm?
No. Use the torque measured at that same rpm, because torque changes across the rev range.