Torque to Horsepower Calculator — Nm / lb-ft to HP & kW
Enter an engine's torque and rotational speed (RPM) to get output power in horsepower, kilowatts and metric PS. Works with both Newton-metres and pound-feet.
Nm
Torque unit
RPM
Mechanical horsepower at the given torque and engine speed
- 1
Convert to lb-ft
250 ÷ 1.35582 = 184.391 lb-ft = 1.35582 Nm. - 2
Intermediate product
184.39 × 3,000 = 553,170.77 - 3
Horsepower
553,170.77 ÷ 5,252 = 105.3HP = lb-ft × RPM ÷ 5,252 (1 HP = 33,000 ft·lbf/min).
How does this calculator work?
Power = Torque × RPM ÷ 9549 (kW, with Nm) or ÷ 5252 (HP, with lb-ft). Enter your engine torque and speed to get horsepower, kilowatts, and metric PS instantly — with a power-vs-RPM curve at constant torque.
Formula
How this is calculated
Power is the rate at which torque is delivered. Torque describes the rotational force an engine produces; power connects that force to how quickly it spins. The relationship is: Power (kW) = Torque (N·m) × RPM ÷ 9549.3. That divisor comes from unit conversion: 1 kW = 1000 W = 1000 N·m/s, and one revolution per minute = 2π/60 radians per second, so kW = N·m × RPM × 2π / (60 × 1000), which simplifies to ÷ 9549.3. The imperial version uses pound-feet and the 5252 constant (33,000 ft-lbf/min ÷ 2π ≈ 5252.1).
Metric horsepower (PS, Pferdestärke) is defined as 735.499 W — slightly less than the US mechanical horsepower of 745.7 W. European car manufacturers publish PS figures; US manufacturers publish HP. The difference is about 1.4% at any given power level.
The XY curve shows how power scales linearly with RPM at the torque you entered. In a real engine the torque varies across the rev range, so the power curve is not linear — it peaks where the product of torque and RPM is highest. This calculator converts a single operating point.
Frequently asked questions
5252 is 33,000 ÷ 2π. One mechanical horsepower is defined as 33,000 foot-pounds per minute. Dividing by 2π converts one revolution into radians, so the formula HP = lb-ft × RPM ÷ 5252 handles all unit conversions at once.
Mechanical HP = 745.7 W; metric PS = 735.499 W. They differ by about 1.4%. European and Japanese spec sheets quote PS; US and UK sheets usually quote mechanical HP. At 100 units the gap is less than 2 units.
Neither — it converts whatever torque you enter. If you enter a dyno-measured wheel torque value you get wheel power; if you enter the manufacturer's engine torque rating you get crankshaft power. Drivetrain losses (typically 15–20%) account for the difference.
Also known as
TG we-Calculate Editorial Team. (2026). Torque to Horsepower Calculator — Nm / lb-ft to HP & kW [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/torque-to-horsepower-calculator
TG we-Calculate Editorial Team. "Torque to Horsepower Calculator — Nm / lb-ft to HP & kW." TG we-Calculate. 2026. https://we-calculate.com/calculator/torque-to-horsepower-calculator.
TG we-Calculate Editorial Team, "Torque to Horsepower Calculator — Nm / lb-ft to HP & kW," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/torque-to-horsepower-calculator
@misc{wecalculate_torque_to_horsepower_calculator, title = {Torque to Horsepower Calculator — Nm / lb-ft to HP & kW}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/torque-to-horsepower-calculator}}, year = {2026}, note = {TG we-Calculate} }
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