Enter your engine horsepower and select your drivetrain type (FWD, RWD, or AWD) to calculate your wheel horsepower (WHP) — the actual power delivered to the ground. You'll also see your drivetrain loss in both HP and percentage, so you know exactly how much power is lost between the engine and the wheels.
Wheel Horsepower (WHP)
--
Drivetrain Loss
--
Loss Percentage
--
Crankshaft Horsepower
--
HP (horsepower) typically refers to power measured at the crankshaft or flywheel — the raw output of the engine. WHP (wheel horsepower) is the power actually measured at the driven wheels after accounting for losses through the transmission, driveshaft, differentials, and other drivetrain components. WHP is always lower than crank HP and represents the power that actually propels the vehicle.
Typical drivetrain losses range from about 15% to 25% depending on the drivetrain layout. Front-wheel drive (FWD) vehicles generally lose around 15%, rear-wheel drive (RWD) around 18%, and all-wheel drive (AWD) systems typically lose around 20% or more due to the additional mechanical components required to power all four wheels.
AWD systems require additional hardware — a transfer case, extra driveshafts, and multiple differentials — to distribute power to all four wheels. Each of these components introduces mechanical friction, which consumes energy and results in higher overall drivetrain losses compared to simpler two-wheel-drive layouts.
WHP is arguably more meaningful for real-world performance because it measures the power that actually reaches the ground. Manufacturers advertise crank HP because it's a higher number, but when comparing two cars head-to-head on a dyno, WHP gives a more accurate picture of true performance potential.
A dynamometer (dyno) is a device that measures the power output of an engine or vehicle. A chassis dyno places the driven wheels on rollers and measures torque and RPM directly at the wheel surface, producing a WHP figure. This is considered a real-world measurement because it captures all drivetrain losses automatically.
Yes. To convert WHP to engine HP, use the formula: HP = WHP / (1 − drivetrain loss %). For example, if your car makes 250 WHP with a RWD drivetrain (18% loss), the estimated crank HP would be 250 / 0.82 ≈ 305 HP. This calculator works in the HP-to-WHP direction, but the math is easily reversible.
No — these percentages are widely accepted averages used as rule-of-thumb estimates. Actual losses depend on many factors including specific transmission type (manual vs. automatic), fluid temperatures, vehicle age, modifications, tire pressure, and more. For precise figures, a professional dyno test on your specific vehicle is the only accurate method.
Yes, transmission type plays a role. Manual transmissions are generally more mechanically efficient than automatic transmissions, meaning they tend to lose slightly less power. Continuously variable transmissions (CVTs) and older torque-converter automatics can have higher losses, while modern dual-clutch automatics are much more efficient. The estimates in this calculator use average values across transmission types.