About WHP to HP Calculator

Users can use this tool to convert wheel horsepower (WHP) into estimated engine horsepower (HP) with ease. Built for mechanics, car enthusiasts, and performance tuners, the calculator simplifies drivetrain loss so users can better estimate dyno numbers, compare setups, and understand engine output.

How to Convert WHP to HP?

When converting WHP to HP, you must consider the power lost in your car's drivetrain. This is also referred to as drivetrain loss. The standard conversion formula to use is:

HP = WHP / (1 - Drivetrain Loss Percentage)

The average loss in drivetrains is:

Solved example

Let’s say you have a Rear-Wheel Drive (RWD) vehicle that produced 350 WHP on a dyno. Assuming an 18% drivetrain loss (0.18):
HP = 350 / (1 - 0.18)
HP = 350 / 0.82
HP = 426.82
Your engine is producing approximately 427 engine horsepower.

Calculate Engine Horsepower Using This Calculator

Follow the given steps to use this tool and get the engine horsepower.

1. Enter the wheel horsepower value.
2. Select the drivetrain loss (Front wheel, Rear wheel, or All wheel)
3. Click 'Calculate.'
4. The calculator then quickly gives you your estimated engine horsepower (HP).

WHP vs. HP

WHP refers to wheel horsepower. Meanwhile, engine horsepower (HP) is known as brake horsepower (BHP) or crank horsepower. The difference is in where the power is measured. Engine horsepower is a measure of how much power your engine can produce before any power leakage in the transmission, driveshaft, and axle. The number of wheel horsepower is typically 20%-45% less than the number of engine horsepower.

WHP to Crank HP Conversion

Use cases of the WHP to HP calculator

• Performance Tuning: Accurately evaluate the impact of aftermarket engine modifications by knowing your true crank horsepower.
• Vehicle Comparisons: Compare your heavily modified car against factory specs, which are always advertised in engine HP.
• Buying and Selling: Provide transparent and accurate power figures when listing a performance vehicle on the US market.
• Motorsport Prep: Ensure your vehicle meets specific class regulations that strictly measure engine power output.

Frequently Asked Questions

What is WHP, and how is it different from HP?

HP refers to the power output at the crankshaft of the engine. WHP refers to the power that is delivered to the wheels.

Why is WHP always lower than HP?

Due to friction and resistance of the different parts of the drivetrain, some power is lost.

Which drivetrain do you think has the biggest power loss?

Because of the extra moving parts, the AWD system typically has the highest loss (about 20-25%).

Does it matter what car I use the calculator on?

As long as you have the WHP and drivetrain type, it can be used on any car.

Is the power loss in an automatic and manual transmission the same?

No, an automatic tends to have slightly more power loss than a manual.

Does the size of my tires have an effect on my WHP?

Yes, larger and heavier tires tend to lower WHP.

Is this tool free to use?

Yes, the calculator is free.

How do I find my vehicle’s drivetrain type?

You can find this in your owner’s manual or by searching online for the make and model of your car.