Horsepower Calculator
Compute engine horsepower from torque and RPM for either lb·ft or N·m, with the result in both horsepower (HP) and kilowatts (kW).
Category: Cars & Vehicles
About this tool
What Is Horsepower Calculator? The Horsepower Calculator converts an engine's torque and rotational speed into mechanical horsepower. Given a torque value in either pound-feet (lb·ft) or newton-meters (N·m) and an engine RPM, it returns the power in both horsepower (HP) and kilowatts (kW). How It Works Power and torque are related by rotational speed. For imperial units, horsepower equals lb·ft torque multiplied by RPM divided by 5252; for metric torque it uses the constant 7127. The tool applies the constant that matches the unit you select, then separately converts the result to kilowatts using the 1 HP = 0.7457 kW factor. Worked Example A turbocharged engine producing 300 lb·ft at 5000 RPM gives 300 × 5000 ÷ 5252 ≈ 285.6 HP, about 213 kW. The same torque expressed as 407 N·m at the same RPM gives 407 × 5000 ÷ 7127 ≈ 285.6 HP, confirming both unit systems agree. Common Use Cases compare engine outputs that are quoted only in torque and RPM roughly estimate whether a tuning goal is realistic for a power target check a manufacturer dyno sheet against its headline horsepower figure Important Notes this is the standard shaft-power relation; real loss, efficiency, and air/temperature corrections are not modelled pick the unit that matches your dyno sheet — mixing lb·ft with N·m changes the result the 5252 constant makes the HP and lb·ft curves cross at 5252 RPM by definition Relat