Worked example
350 bhp at the crank and 300 WHP gives a 50 hp difference, or about 14.3% of the crank figure.
Why call it a difference rather than a measured loss?
Crank and wheel figures may come from different test equipment, correction standards, temperatures or even different vehicle states. The arithmetic difference is clear; attributing every horsepower to drivetrain friction can overstate what the data proves.
Known only one figure?
If you know only WHP and want to explore assumed crank power, use the WHP-to-HP calculator where the loss percentage is an explicit adjustable assumption.