Crank to wheel hp calculatorAn honest estimate, not a promise

The formula

Wheel hp = crank hp × (1 − loss), and crank hp = wheel hp ÷ (1 − loss). With a 15% loss, 400 hp at the crank is 340 whp, and 340 whp is 400 hp at the crank.

A common mistake is to add 15% to a wheel figure: 340 whp × 1.15 is 391 hp, not 400. Divide, don't multiply.

Crank hp to wheel hp table

How much of the engine's power reaches the wheels, at 10%, 15% and 20% loss. For example, 300 hp at the crank is about 240 to 270 whp.

Whp to crank hp table

The same formula for round wheel figures, at 10%, 15% and 20% loss. For example, 700 whp is about 778 to 875 hp at the crank.

How big is the loss really?

There is no single number. The gearbox, differential and tyres all turn some power into heat, and dynos and weather correction differ too. Three real examples from our guides:

• Nissan GT-R R35: Nissan rates the 2017 US car at 565 hp, and Cobb measured a stock one at 501 whp, about 11% lower (guide).
• Mercedes-AMG C63 S: RENNtech quotes 601 hp at the engine and 517 whp, assuming a 14% loss (guide).
• Litchfield's LM1000 GT-R: 1,047 bhp at the engine and 824 at the wheels, about 21% lower.

So treat the result as a range, and compare tunes on the same dyno. More in Crank hp or wheel hp?

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