Horsepower, Torque & Wheel HP Calculator

Convert torque to horsepower at any RPM, and turn a dyno's wheel horsepower into an estimated crank horsepower using typical FWD, RWD and AWD drivetrain losses.

Torque → horsepower

Horsepower at 5,500 rpm
146.6 hp
109.3 kW · 190 Nm

Wheel hp → crank hp

Estimated crank hp
153 hp
23 hp lost in the drivetrain

Horsepower = torque × RPM ÷ 5252

Horsepower isn't measured directly. An engine dyno measures torque and multiplies it by RPM. The 5252 comes from how James Watt defined one horsepower (33,000 lb-ft per minute) divided by 2π. That's also why every torque and horsepower curve in lb-ft and hp crosses at exactly 5,252 rpm.

Wheel hp vs crank hp

Factory ratings are at the crank (flywheel). A chassis dyno measures at the wheels, after the transmission, driveshaft, differential and axles have taken their cut. Common rules of thumb are about 10–15% loss for front-wheel drive, 12–18% for rear-wheel drive and 18–25% for all-wheel drive.

The truth is messier. Losses are partly a fixed amount rather than a percentage, and different dyno brands read differently (a Dynojet often reads higher than a Mustang dyno). Use crank estimates to compare against factory numbers, not to win arguments. Compare before-and-after pulls on the same dyno, same day, to judge a mod.