Wheel horsepower ⇄ crank horsepower
WHP to HP Calculator
A dyno measures horsepower at the wheels, while manufacturers quote it at the crankshaft. The difference is drivetrain loss. Use this converter to estimate either figure from the other.
- Assumed loss
- 15.0 %
- Crank in kW
- 298 kW
- Range at 10% loss
- 378 hp
- Range at 20% loss
- 425 hp
How wheel horsepower converts to crank horsepower
If the drivetrain loses a fraction L of the engine’s power, then WHP = HP × (1 − L) and HP = WHP ÷ (1 − L). The commonly used rule-of-thumb losses are about 12% for front-wheel drive, 15% for rear-wheel drive and 20% for all-wheel drive, with around 10% for EVs and motorcycles. For 340 whp on RWD that works out to 400 hp at the crank.
Drivetrain loss rule of thumb
| Drivetrain | Assumed loss | 300 whp → crank hp |
|---|---|---|
| FWD | 12% | 341 |
| RWD | 15% | 353 |
| AWD | 20% | 375 |
| EV / motorcycle | 10% | 333 |
The percentages are estimates, not measurements. Real loss depends on transmission type, wheel and tyre mass, dyno type and conditions, so two dynos can disagree by several percent.
Using the result
Feed the crank horsepower into the quarter mile calculator for a prediction. The 1/4 mile estimator does the conversion for you.
Frequently asked questions
How much horsepower is lost to the drivetrain?
Typically 10–20%. FWD about 12%, RWD about 15%, AWD about 20% are common rules of thumb.
Is dyno horsepower the same as advertised horsepower?
No. Dynos measure at the wheels. Advertised numbers are at the crank, usually higher.
How do I convert hp to whp?
Multiply by (1 − loss). A 400 hp RWD car would make about 340 whp at 15% loss.
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