Last updated October 13, 2026 · Report an error
Horsepower is calculated directly from torque and rotational speed using a fixed mechanical engineering formula.
This calculator converts torque and RPM into horsepower, and also shows the equivalent in kilowatts and watts.
How it works
Enter the torque in pound-feet and the engine speed in RPM. The calculator applies the standard formula \(\text{HP} = \dfrac{\text{Torque} \times \text{RPM}}{5252}\), where 5252 is the constant at which the torque and horsepower curves always cross on a dyno chart.
- Enter torque (lb-ft).
- Enter engine speed (RPM).
- Click Calculate to see your results.
Examples
300 lb-ft at 5252 RPM
An engine producing 300 lb-ft of torque at exactly 5252 RPM produces exactly 300 horsepower — the point where the torque and horsepower curves cross.
Who should use it
- Converting a dyno chart's torque and RPM reading into horsepower.
- Checking mechanical engineering coursework involving torque-horsepower relationships.
Industry applications
- Automotive engineering and performance tuning
- Mechanical engineering education
Advantages
- Simple, exact mechanical engineering formula — no rules of thumb involved.
- Includes kilowatt and watt conversions alongside horsepower.
Limitations
- Requires torque in lb-ft — needs manual conversion first if you only have Newton-meters.
Common mistakes to avoid
- Entering torque in Newton-meters instead of pound-feet, which this calculator expects.
- Confusing peak torque RPM with peak horsepower RPM — they usually occur at different points on an engine's power curve.
Best practices
- Use torque and RPM values from the same point on a dyno chart, not the peak torque and peak RPM figures independently.
Tips
- On any torque/horsepower dyno graph, the two curves always intersect at exactly 5252 RPM — a handy way to sanity-check a chart's accuracy.
Frequently asked questions
Yes, with no signup and no limit on how many calculations you run.
It comes from unit conversion: 1 horsepower = 33,000 ft-lb/min, and one revolution covers 2π radians, so 33,000 / (2π) ≈ 5252 — the exact constant that makes torque and horsepower curves cross at that RPM.
Yes — the same torque-times-RPM relationship applies to any rotating shaft, whether driven by a combustion engine or an electric motor.
Because of the formula's constant — at exactly 5252 RPM, the numeric value of horsepower always equals the numeric value of torque in lb-ft, regardless of the engine.