Flywheel HP vs Wheel HP Calculator

Car manufacturers rate engine output at the crankshaft (flywheel HP), but power is always lost through the transmission and axles before it reaches the wheels — the Flywheel HP vs Wheel HP Calculator converts between the two. Enter your horsepower value, select whether it's flywheel or wheel HP, then choose your drivetrain type (FWD, RWD, or AWD) and transmission type to get the converted power. Secondary outputs show your drivetrain loss percentage, power lost in HP, and overall drivetrain efficiency.

HP

Enter the horsepower value you want to convert

Power Source *

Select your vehicle's drivetrain configuration

Transmission type affects drivetrain loss

Results

Converted Power

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Drivetrain Loss

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Power Lost

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Drivetrain Efficiency

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Frequently Asked Questions

What is the difference between flywheel HP and wheel HP?

Flywheel horsepower is the power measured at the engine's crankshaft, while wheel horsepower is the power that actually reaches the wheels after drivetrain losses. Wheel HP is always lower due to friction and mechanical losses in the transmission, differential, and driveshafts.

How much power is lost through the drivetrain?

Typical drivetrain losses range from 10-25% depending on the configuration. Front-wheel drive vehicles typically lose 10-15%, rear-wheel drive loses 15-20%, and all-wheel drive systems can lose 20-25% or more due to additional components.

Why do automatic transmissions have higher losses than manual?

Automatic transmissions use a torque converter and hydraulic systems that create more internal friction and parasitic losses compared to the direct mechanical connection in manual transmissions. This typically results in 2-5% additional power loss.

Which horsepower measurement is more accurate for performance?

Wheel horsepower is more accurate for real-world performance because it represents the actual power available to move the vehicle. However, flywheel HP is commonly used by manufacturers because it shows higher numbers and represents the engine's theoretical maximum output.

How does drivetrain type affect power loss?

AWD systems have the highest losses due to transfer cases, additional differentials, and more driveshafts. RWD has moderate losses from the transmission, driveshaft, and rear differential. FWD has the lowest losses with the shortest power path from engine to wheels.

Can I use this calculator for modified vehicles?

Yes, but keep in mind that heavily modified drivetrains, aftermarket transmissions, or performance differentials may have different loss characteristics than stock configurations. The calculator provides estimates based on typical factory drivetrain losses.

What factors can increase drivetrain losses?

Factors that increase losses include worn components, thick gear oil, tight differentials, heavy wheels/tires, and additional accessories like power steering pumps or air conditioning compressors that are driven by the engine.