The math
Two old empirical formulas have predicted quarter-mile times for decades. They both depend on a single ratio: power divided by weight.
ET ≈ 5.825 × ∛(weight ÷ WHP)
trap ≈ 234 × ∛(WHP ÷ weight)
Wheel horsepower is the figure that matters. Crank numbers from a marketing sheet need to be discounted by the drivetrain - typically 10–25% depending on transmission and driveline.
Frequently asked
Why isn’t my real ET matching the calculator?
Calculator outputs assume a clean launch, sticky surface, and that the formula constants describe your car. Real-world runs are dragged down by wheelspin off the line, slow shifts, narrow tires, ethanol-free fuel choices, hot air, and altitude. A street tire alone can add half a second.
Should I use the “1-foot rollout” setting?
Yes if you’re comparing to drag-strip timeslips. NHRA timing starts 1 foot past the staging beam, which makes ETs about 0.3 seconds quicker than a true zero-roll measurement. Off-strip dyno-style comparisons should use rollout off.
What traction setting fits a stock daily driver?
Average street. Sticky is for drag radials on prepped concrete. Poor is for snow tires or rain. Very poor is for a smoky burnout - useful mostly to see how punishing wheelspin actually is.