Using the Horsepower Calculator
Torque must be in newton-meters and speed in revolutions per minute. The formula converts RPM to angular velocity before multiplying by torque. Use torque measured at the same operating speed as the RPM entry rather than combining unrelated peak figures.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Torque (N·m)
- 250
- Engine speed (RPM)
- 4000
Example result
- Mechanical horsepower
- 140.4315
- Power (kW)
- 104.71976
Method and assumptions
Power = torque × angular velocity. Uses mechanical horsepower, not metric PS.
Use torque and speed from one operating point
A power curve describes many operating points rather than a single universal output. Pair each torque reading with the rotational speed at which it was obtained. Repeat the calculation for other points if you want to compare them. Keep mechanical horsepower and kilowatts labeled, and avoid mixing engine-shaft measurements with wheel measurements.
Common question
Can two machines have the same torque but different horsepower?
Yes. At the same torque, the one operating at a higher rotational speed produces more power in this model. Torque alone does not determine horsepower; the speed at which that torque is delivered is also needed.
Guide updated .