Calculate engine power in kW, horsepower and metric horsepower from torque and engine speed. Enter your values; the result updates as you type, with the method shown below.
About this calculator
An engine’s power comes from its torque and its speed. This calculator turns torque in N·m and rpm into kilowatts, metric horsepower and horsepower, and gives the torque in lb·ft.
Enter the torque and the engine speed.
When to use it
- Reading a car or motorbike spec sheet.
- Comparing engines.
- Tuning and dyno results.
- Mechanics training.
How to read the result
Power (kW) = torque × rpm / 9,549. 250 N·m at 4,000 rpm gives about 104.7 kW, or 142 metric hp.
Peak torque and peak power usually occur at different engine speeds.
Mistakes to avoid
- Using peak torque with the rpm of peak power.
- Mixing metric and mechanical horsepower.
- Using lb·ft as N·m.
Formula
P (kW) = torque (N·m) × rpm / 9549
Worked example
250 N·m at 4,000 rpm: 104.7 kW, 140 hp, 142 metric hp.
Frequently asked questions
hp or metric hp?
1 kW = 1.341 hp (imperial) or 1.360 metric hp (ch, CV, PS).
Why does power depend on rpm?
Power is torque times rotation speed.
Why 9,549?
It converts rpm and N·m into kW (60,000 / 2π).
What is the difference between hp and ch?
1 hp ≈ 745.7 W, 1 metric hp ≈ 735.5 W.
Is torque or power more important?
Torque gives pulling force; power sets top performance.
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Results are estimates for information only. Check important figures with a professional.