United States version
What this tool answers
Engine torque and rotational speed determine mechanical power at the stated operating point. Displacement supplies context, such as power per litre; displacement alone does not determine measured power. Older input sets without torque retain their clearly labelled airflow heuristic.
Formula
Power (W) = torque (N·m) × RPM × 2π / 60; mechanical hp = W / 745.699871582.
Worked example: Power at a specified operating point
A 2.0-litre engine producing 300 N·m at 4,000 RPM has 125.66 kW, or 168.52 mechanical hp. This is power at that operating point, not a predicted peak or wheel-power measurement.
Load these worked-example inputs
Limitations
The torque must correspond to the entered RPM. Wheel and crankshaft measurements differ. The retained airflow heuristic is not a dynamometer measurement and should not be used as a design or performance guarantee.
Frequently asked questions
Does displacement alone give engine horsepower?
No. Torque and rotational speed determine power at an operating point; displacement is contextual.
Why must torque and RPM come from the same operating point?
Combining peak torque at one speed with a different speed does not describe a measured power point.
What happens to an older airflow-only example?
With no torque value, the old displacement, RPM and efficiency calculation remains available and is explicitly identified as a heuristic.