How this calculator works
These empirical cube-root correlations relate quarter-mile performance to pounds per mechanical horsepower. Race mass includes driver, fuel and equipment. The power basis is peak engine power rather than an unadjusted wheel-dynamometer value. Huntington, Fox and Hale used different fits; their outputs are estimates, and launch traction, gear changes, weather and drag can change a measured run substantially. Elapsed time excludes reaction time. The Fox constants here are the later 2001 values, not constants from the 1973 theoretical article.
Formula
ET=A(W_lb/P_hp)^(1/3); trap_mph=B(P_hp/W_lb)^(1/3). (A,B): Huntington (6.290,224), Fox (6.269,230), Hale (5.825,234).
Worked example
For 8000 lb and 1000 hp, the mass-to-power ratio is 8. Its cube root is 2, so Hale predicts 11.65 s and 117 mph. Fox predicts 12.538 s and 115 mph.
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Frequently asked questions
Which correlation should I use?
Compare them as historical estimates. Their differences show part of the uncertainty; none simulates an individual car.
Can elapsed time and trap speed give different power estimates?
Yes. Launch and shifting affect elapsed time strongly, and the two correlations were fitted independently.
Does power mean kilowatts or horsepower?
The unit selector accepts both. The equations internally use mechanical horsepower, about 745.699872 W per hp.