What is Wheel Horsepower?

Wheel horsepower is the actual power available at the driving wheels of a car. Unlike the engine or crank horsepower, which manufacturers often highlight, wheel horsepower accounts for energy losses in the drivetrain during power transmission.

Bhp to whp Calculation Formula:

The formula for wheel horsepower (WHP) is given by:



  • WHP is the wheel horsepower.
  • ηdvtr​ is the efficiency of power transmission of the drivetrain.
  • EHP is the engine horsepower (also known as crank or brake horsepower).

Drivetrain Systems:

Cars can have different drivetrain systems:

  • Front-wheel drive (FWD)
  • Rear-wheel drive (RWD)
  • All-wheel drive (AWD) or Four-wheel drive (4WD)

Drivetrain Loss Calculation

The drivetrain introduces losses in power transmission due to various components. Drivetrain loss depends on the efficiency of these components.

Front-Wheel Drive Efficiency Formula:



  • ηFWD​ is the efficiency of the front-wheel drive system.
  • ηgbx​ is the efficiency of the gearbox.
  • ηdif​ is the efficiency of the differential.
  • ηfdrs​ is the efficiency of the front drive shaft.

Rear-Wheel Drive Efficiency Formula:



  • ηRWD​ is the efficiency of the rear-wheel drive system.
  • ηprs​ is the efficiency of the propeller shaft.
  • ηrdrs​ is the efficiency of the rear drive shaft.

Drivetrain Loss Calculation Formula:

Drivetrain Loss=1−ηdvtr

Drivetrain hp loss=(1−ηdvtr​)⋅EHP=EHPWHP

Efficiency of Drivetrain Components

Gearbox Efficiency Formula:



  • ηgbx​ is the gearbox efficiency.
  • ηbrg​ is the bearing efficiency.
  • Nbrg​ is the number of bearings.
  • ηgrm​ is the gear mesh efficiency.
  • Ngrm​ is the number of gear meshes.

Propeller Shaft Efficiency Formula:



  • ηprs​ is the propeller shaft efficiency.
  • ηuj​ is the universal joint efficiency.
  • Nuj​ is the number of universal joints.

Differential Efficiency Formula:



  • ηdif​ is the differential efficiency.
  • ηbrg​ is the bearing efficiency.
  • Nbrg​ is the number of bearings.
  • ηgrm​ is the gear mesh efficiency.

Drive Shaft Efficiency Formula:



  • ηdrs​ is the drive shaft efficiency.
  • ηtrp​ is the tripod joint efficiency.
  • ηrzp​ is the Rzeppa joint efficiency.

How to Calculate Wheel Horsepower?

  1. Determine Drivetrain Efficiency:
    • Use the wheel horsepower calculator to find the drivetrain efficiency.
  2. Multiply with Engine Horsepower:
    • Multiply the drivetrain efficiency with the engine horsepower to obtain wheel horsepower.
  3. Verify with Calculator:
    • Confirm the result using the wheel horsepower calculator.

How to Use the Wheel Horsepower Calculator?

  1. Select Drive Type:
    • Choose between Rear-wheel drive or Front-wheel drive.
  2. Enter Engine Horsepower:
    • Input the vehicle’s engine horsepower.
  3. Enter Component Efficiencies:
    • Fill in the efficiencies for gearbox, propeller shaft, differential, and drive shaft. Advanced mode allows entering individual efficiencies.
  4. Get Wheel Horsepower:
    • The calculator will provide the calculated wheel horsepower.


Q: What is the wheel horsepower of a 660 bhp rear-wheel drive vehicle?

A: The wheel horsepower is 539.4 hp. Multiply brake horsepower by the assumed drivetrain efficiency (0.8173).

Q: What is the drivetrain loss of a 118 bhp car if the wheel horsepower is 95 hp?

A: The drivetrain loss is 23 hp. Subtract wheel horsepower from brake horsepower.

Q: Which drivetrain system has maximum efficiency?

A: Front-wheel drive systems generally have the highest efficiency due to fewer power transmission components.

Note: This information is provided in simplified terms for better understanding. For precise calculations, the wheel horsepower calculator is recommended.

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