HP to WHP Calculator
Evaluate wheel horsepower (WHP) from engine crank horsepower (HP) and drivetrain loss, or convert chassis dyno logs back to crank engine limits. Settle build parameters dynamically.
HP to WHP Converter
How to Use the HP to WHP Calculator
Converting engine crankshaft horsepower (HP) to wheel horsepower (WHP) is direct.
- 1Enter Engine HP: Input the rated crankshaft power rating in horsepower.
- 2Enter Drivetrain Loss: Input the percentage of power lost through frictional mechanical resistance (typically 10% to 25%).
- 3Calculate: Click the "Calculate to WHP" button to run the conversion.
How to Convert HP to WHP
In automotive engineering, engine horsepower (often referred to as crank horsepower, BHP, or flywheel horsepower) measures the mechanical power output generated directly at the crankshaft. However, before this power reaches the road, it must pass through drivetrain components including the clutch or torque converter, transmission, driveshaft, differential, and axles. Mechanical friction, gear meshing, and rotational inertia in these parts absorb energy, creating a drivetrain loss. Wheel horsepower (WHP) represents the actual usable power measured at the tires. Sizing performance builds, calibrating track setups, and comparing dyno sheets requires converting engine horsepower to wheel horsepower.
Real-Life Sizing Scenarios
Scenario 1: Sizing WHP for a Rear-Wheel Drive Performance Build
An automotive tuner estimates the wheel power of a modified sports car producing 450 HP at the crank with a typical RWD manual drivetrain loss of 15%:
WHP = 450 HP × (1 − 0.15) = 382.50 WHP
Scenario 2: Sizing WHP for an All-Wheel Drive Vehicle
A technician calculates wheel power for a 250 HP utility vehicle experiencing a higher AWD drivetrain loss of 22%:
WHP = 250 HP × (1 − 0.22) = 195.00 WHP
Step-by-Step Manual Sizing Guide
- 1Identify engine metrics: Settle the rated crankshaft horsepower and the drivetrain loss percentage.
- 2Apply the Sizing Formula: Write:
WHP = HP × (1 − Drivetrain Loss ÷ 100). - 3Solve the calculation: Subtract the decimal loss from 1, and multiply the engine horsepower by the result to find WHP.
HP to WHP Conversion Chart
The table below displays engine crankshaft horsepower ratings and their estimated wheel horsepower outputs at typical drivetrain losses (15% manual RWD and 20% automatic AWD):
| Crank Power (HP) | Estimated WHP (15% Loss) | Estimated WHP (20% Loss) |
|---|---|---|
| 100 HP | 85.00 WHP | 80.00 WHP |
| 200 HP | 170.00 WHP | 160.00 WHP |
| 250 HP | 212.50 WHP | 200.00 WHP |
| 300 HP | 255.00 WHP | 240.00 WHP |
| 400 HP | 340.00 WHP | 320.00 WHP |
| 500 HP | 425.00 WHP | 400.00 WHP |
| 700 HP | 595.00 WHP | 560.00 WHP |
| 1000 HP | 850.00 WHP | 800.00 WHP |
500 WHP to HP
Converting a dyno measurement of 500 WHP back to engine crank horsepower at a standard 15% drivetrain loss:
Engine HP = 500 WHP ÷ (1 − 0.15) = 588.24 HP
300 WHP to HP
Converting a dyno measurement of 300 WHP back to engine crank horsepower at a standard 15% drivetrain loss:
Engine HP = 300 WHP ÷ (1 − 0.15) = 352.94 HP
200 WHP to HP
Converting a dyno measurement of 200 WHP back to engine crank horsepower at a standard 15% drivetrain loss:
Engine HP = 200 WHP ÷ (1 − 0.15) = 235.29 HP
250 WHP to HP
Converting a dyno measurement of 250 WHP back to engine crank horsepower at a standard 15% drivetrain loss:
Engine HP = 250 WHP ÷ (1 − 0.15) = 294.12 HP
400 WHP to HP
Converting a dyno measurement of 400 WHP back to engine crank horsepower at a standard 15% drivetrain loss:
Engine HP = 400 WHP ÷ (1 − 0.15) = 470.59 HP
700 WHP to HP
Converting a dyno measurement of 700 WHP back to engine crank horsepower at a standard 15% drivetrain loss:
Engine HP = 700 WHP ÷ (1 − 0.15) = 823.53 HP
Frequently Asked Questions (FAQs)
A chassis dyno reading of 1000 WHP corresponds to approximately 1176.47 HP at the engine crankshaft, assuming a typical drivetrain loss of 15%. If the vehicle uses an all-wheel drive layout with a 20% loss factor: HP = 1000 ÷ 0.80 = 1250 HP.
For a standard drivetrain loss of 15%, 450 WHP is equivalent to exactly: HP = 450 ÷ (1 − 0.15) = 529.41 HP at the crank. If FWD manual losses are only 12%: HP = 450 ÷ 0.88 = 511.36 HP.
At a standard 15% drivetrain loss, 280 WHP equals 329.41 HP at the crankshaft. For a manual front-wheel drive (FWD) car with a lower loss factor of 12%: HP = 280 ÷ 0.88 = 318.18 HP.
At a standard 15% drivetrain loss, a dyno output of 250 WHP corresponds to exactly: HP = 250 ÷ 0.85 = 294.12 HP of active engine crank power.
An 800 WHP wheel power rating corresponds to approximately 941.18 HP at the engine crankshaft (at 15% loss). For an AWD drivetrain setup with a 20% loss factor: HP = 800 ÷ 0.80 = 1000 HP.
At a standard 15% drivetrain loss, 480 WHP translates to exactly: HP = 480 ÷ 0.85 = 564.71 HP at the crankshaft.
