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Engine horsepower calculator

Convert shaft torque and rotational speed to power: watts = torque × rpm × 2π/60.

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Answer

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Convert shaft torque and rotational speed to power: watts = torque × rpm × 2π/60.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
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Formula and assumptions
Mechanical horsepower = 550 ft·lbf/s = 745.6998715822702 watts. This is the torque at the entered speed, not peak torque substituted at another rpm. No wheel-to-crank loss, engine model or dynamometer measurement is inferred.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
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Using Engine horsepower calculator
Convert shaft torque and rotational speed to power: watts = torque × rpm × 2π/60.
Mechanical horsepower = 550 ft·lbf/s = 745.6998715822702 watts. This is the torque at the entered speed, not peak torque substituted at another rpm. No wheel-to-crank loss, engine model or dynamometer measurement is inferred.
Next: Torque calculator
Next: Engine torque calculator
A worked example
Example inputs: torque (n·m) = 100, engine speed (rpm) = 3000. Mechanical horsepower = 42.1294514497.
Before you use the result
Mechanical horsepower = 550 ft·lbf/s = 745.6998715822702 watts. This is the torque at the entered speed, not peak torque substituted at another rpm. No wheel-to-crank loss, engine model or dynamometer measurement is inferred.
Example results for torque (n·m)
These examples use Engine speed (rpm): 3000. They are reference calculations, not recommended settings.
Torque (N·m)Mechanical horsepower
5021.0647257249
10042.1294514497
20084.2589028995
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ToolOctopus. “Engine horsepower calculator.” Updated 2026-09-26. https://tooloctopus.com/engine-horsepower-calculator.
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