Choose a mode to convert between horsepower units, or calculate horsepower from torque and RPM.

How to Use the Horsepower Calculator

Unit Conversion mode takes one value and one unit — Mechanical HP, Metric HP (PS), kilowatts, or watts — and shows the equivalent in all four. Torque & RPM mode takes those two numbers directly and returns horsepower.

"Horsepower" hides two different, non-interchangeable definitions. Mechanical (imperial) horsepower, the one used in the US and UK, equals 745.7 watts. Metric horsepower — PS, short for Pferdestärke, still the standard on European and Japanese spec sheets — equals 735.5 watts, about 1.4% smaller. A car advertised at "300 PS" in Germany is not making the same power as a "300 hp" rating in the US; converted to a common unit, 300 PS comes out to roughly 296 mechanical hp.

1 mechanical HP = 745.7 W
1 metric HP (PS) = 735.5 W
1 kW = 1000 W

Torque and Horsepower Cross at 5252 RPM

The torque/RPM formula:

HP = (Torque in lb-ft × RPM) ÷ 5252

5252 isn't an arbitrary rounding — it falls directly out of horsepower's original definition (33,000 ft-lb per minute) divided by 2π. One consequence worth knowing purely because it's a fun, checkable fact: on any engine's power curve, torque and horsepower are always numerically equal at exactly 5252 RPM, regardless of the engine. Below that RPM, torque reads higher than horsepower; above it, horsepower reads higher — dyno charts cross there every time.