Free Horsepower Calculator Online
Use this free horsepower calculator to convert torque and RPM into horsepower. The calculator also shows equivalent values in kilowatts, BTU/hr, and watts so you can compare power ratings across different systems and standards.
Horsepower
Enter torque and RPM
How the Horsepower Calculator Works
The horsepower calculator uses the standard mechanical formula: HP = (Torque in lb-ft x RPM) / 5,252. The constant 5,252 comes from converting rotational work into the historical unit James Watt defined as 33,000 foot-pounds per minute.
For metric torque (Nm), the horsepower calculator first converts to lb-ft using the factor 1 Nm = 0.7376 lb-ft. A motor producing 400 Nm at 5,000 RPM delivers roughly 295 lb-ft, which equals about 281 HP through the horsepower calculator formula.
Once horsepower is computed, the calculator converts to kW (multiply by 0.7457), BTU/hr (multiply by 2,545), and watts (multiply by 745.7). These conversions are essential for comparing engines, motors, and HVAC equipment rated in different power units.
Power Unit Conversions
The horsepower calculator applies these conversions to your result automatically.
Horsepower in Everyday Life
Cars
A typical sedan produces 150-200 HP. Performance cars reach 400-700 HP. An F1 car generates over 1,000 HP from its hybrid powertrain. Use the horsepower calculator to convert torque specs from different sources.
Electric Motors
Electric motors are often rated in kW. A 75 kW motor equals about 100 HP. Industrial motors range from fractional HP to thousands of HP for large pumps and compressors.
HVAC Systems
Air conditioners and furnaces use BTU/hr ratings. A 3-ton AC unit produces 36,000 BTU/hr, which equals roughly 14 HP of cooling capacity. The horsepower calculator bridges these units.
Frequently Asked Questions
Disclaimer: This horsepower calculator provides theoretical values based on the standard formula. Actual engine output varies with altitude, temperature, fuel quality, and drivetrain losses.