Horsepower Calculator

About This Tool

The Horsepower Calculator converts torque and RPM into horsepower using the standard engine dyno formula. It also converts between common power units including kilowatts, metric horsepower (PS), and brake horsepower (BHP). This is the same formula used by dynamometer software to generate horsepower curves from measured torque data.

The 5,252 Constant

The number 5,252 appears in every horsepower calculation because it is the result of unit conversion constants. One horsepower equals 33,000 foot-pounds of work per minute. When you divide 33,000 by 2 times pi, you get 5,252. This is why horsepower and torque curves always intersect at exactly 5,252 RPM on a dyno chart. Below that RPM, torque is numerically higher than horsepower. Above it, horsepower is higher.

Horsepower vs. Torque

Torque is the rotational force the engine produces. Horsepower is how fast that force is applied over time. An engine with high torque but low RPM (like a diesel truck) can pull heavy loads but accelerates slowly. An engine with lower torque but very high RPM (like a sport bike) produces high horsepower and accelerates quickly but has less low-end pulling force. For straight-line speed, horsepower matters more. For towing and off-the-line response, torque matters more.

Crank vs. Wheel Horsepower

Manufacturer ratings measure horsepower at the crankshaft. By the time power reaches the wheels, 10-20% is lost through the transmission, driveshaft, differential, and axles. A chassis dynamometer measures wheel horsepower (WHP), which is what actually propels the car. When comparing aftermarket modifications, wheel horsepower is the more practical measurement since it shows actual gains at the pavement.