Engine Power Calculator – HP, kW and PS
Calculate engine power in kW, PS and hp from torque and RPM, or estimate power from the quarter-mile time.
Tip: PS and hp are not the same: 1 PS ≈ 0.986 hp ≈ 0.735 kW. When comparing cars, always check which unit the brochure uses.
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About this digital tool
An engine's power is directly related to torque and revolutions per minute: P (kW) = torque (N·m) × RPM ÷ 9549. This calculator does this step for you and shows the result in three units — kW, metric horsepower (PS/CV, the value you see in the car's registration document) and mechanical horsepower (hp, the American standard).
If you don't know the torque, you can estimate power from the car's weight and the quarter-mile time (ET) with the well-known drag formula. Both are theoretical estimates, not dynamometer measurements; power measured at the wheels is usually 10–20% lower than at the flywheel because of drivetrain losses.
How to use
- Choose the method: from torque or from the quarter-mile time
- Enter the torque and choose N·m or lb·ft, then the revolutions (RPM)
- Or enter the car's weight and the quarter-mile time
- Read the power in kW, PS and hp
- Compare with the factory data to estimate the losses
Frequently asked questions
How is engine power calculated from torque?
P (kW) = torque (N·m) × RPM ÷ 9549.3. For example, 350 N·m at 4000 rpm gives about 146.6 kW, that is roughly 199 PS or 197 hp.
What is the difference between PS, CV and hp?
PS and CV are metric horsepower (735.5 W). Hp is mechanical horsepower (745.7 W). So 100 PS ≈ 98.6 hp. In Europe power is often given in kW or PS.
Can I calculate power without knowing the torque?
Yes, roughly: choose the "From quarter-mile time" method, enter the car's weight with the driver and the measured time. It is an estimate, not an exact value.
Why is wheel power lower than engine power?
Part of the energy is lost in the gearbox, drivetrain and friction — usually 10–20%. A wheel dynamometer shows the lower value, while the factory reports flywheel power.
What is torque and in what unit is it given?
It is the turning force the engine produces, measured in N·m (metric) or lb·ft (American). 1 lb·ft = 1.356 N·m. The calculator converts automatically.