Convert Wheel Horsepower to Engine Horsepower
Accurately calculate engine horsepower from wheel horsepower measurements. Account for drivetrain losses in front-wheel, rear-wheel, and all-wheel drive systems.
WHP to HP Calculator
Frequently Asked Questions
Why are HP and WHP different?
HP (Engine Horsepower) refers to the power output directly from the engine, while WHP (Wheel Horsepower) is the actual power that reaches the wheels after accounting for drivetrain losses. These losses occur through the transmission, differential, axles, and other drivetrain components.
What are typical drivetrain losses?
Front Wheel Drive (FWD): 10% - Most efficient due to shorter power path.
Rear Wheel Drive (RWD): 15% - Additional loss through driveshaft and differential.
All Wheel Drive (AWD): 25% - Highest loss due to transfer case and multiple differentials.
What is the WHP to HP formula?
The formula is: HP = WHP × 1 / (1 - DL)
Where HP = Engine Horsepower, WHP = Wheel Horsepower, and DL = Drivetrain Loss (as decimal).
For example: 250 WHP with FWD = 250 × 1 / (1 - 0.10) = 277.78 HP
When should I use this calculator?
Use this calculator when you have dyno results showing wheel horsepower and want to estimate the actual engine output. This is useful for performance comparisons, engine tuning, or understanding power delivery efficiency in your vehicle.
How accurate are these calculations?
These calculations use industry-standard drivetrain loss percentages and provide good estimates. Actual losses can vary based on vehicle condition, drivetrain design, and measurement conditions. For precise measurements, professional dyno testing is recommended.
What affects drivetrain losses?
Drivetrain losses are affected by transmission type (manual vs automatic), differential design, drivetrain condition, lubricant viscosity, and temperature. Performance modifications like lightweight components can reduce losses, while worn parts increase them.