Method
Mechanical hp = torque(lb-ft) × RPM ÷ 5252.113; SI power is torque(N·m) × angular speed(rad/s).
Everyday worksheet
Engine Horsepower Calculator
Estimate mechanical engine power from torque and rotational speed in imperial or SI units.
The calculation runs locally. Results include the intermediate values, unit conversions and assumptions needed to audit the answer.
Method, assumptions and practical use
How the Engine Horsepower Calculator works
Mechanical hp = torque(lb-ft) × RPM ÷ 5252.113; SI power is torque(N·m) × angular speed(rad/s). Inputs stay in this browser, and the result table exposes conversions and assumptions for independent checking.
Interpret the result
Power measures the rate of doing work; torque alone does not determine power without rotational speed.
Check the assumptions
Calculated shaft power ignores drivetrain loss, measurement uncertainty and correction standards.
Local calculation
Everything runs in this browser. Inputs are not sent to an external calculator.
Rounding
Displayed values may be rounded for readability while calculations use full floating-point precision unless the tool explicitly uses exact integers.
Scope
Calculated shaft power ignores drivetrain loss, measurement uncertainty and correction standards.
Simple by design
Three steps to a clearer number.
Enter your details
Use realistic values in each field. You can change them anytime.
Calculate instantly
The formula runs locally, so there is no account or waiting time.
Use the result
Treat the answer as a practical estimate for your next decision.