🏁 Quarter-Mile ET & Trap Speed Calculator
Enter horsepower and weight to estimate the 1/4-mile elapsed time and trap speed.
Estimated 1/4-mile ET
12.95 sec
Trap speed
105.2 mph
169.3 km/h
Estimates from the classic empirical drag-racing formulas: ET ≈ 5.825 × (weight ÷ hp)^⅓ and trap speed ≈ 234 × (hp ÷ weight)^⅓ (pounds and horsepower). These assume a well-set-up rear-drive car with good traction — real times depend heavily on tyres, gearing, launch and aero, so treat them as a ballpark. 🔒 In your browser.
How the quarter-mile et & trap speed calculator works
Drag racers have long estimated quarter-mile performance from just power and weight using empirical formulas fitted to real timeslips. This tool uses the widely-quoted pair: elapsed time ET ≈ 5.825 × (weight ÷ horsepower)^⅓ and trap speed ≈ 234 × (horsepower ÷ weight)^⅓, with weight in pounds. Power-to-weight is what dominates straight-line acceleration, which is why these one-line formulas get surprisingly close for a well-set-up car.
These are ballpark estimates for a traction-limited rear-drive car launching well. Real results swing with tyres, gearing, transmission, aerodynamics, altitude and driver skill — a car that can't hook up will run slower ET despite the same power. Use crank or wheel horsepower consistently and include the driver's weight.
Frequently asked questions
How do I estimate quarter-mile time from horsepower?
A common formula is ET = 5.825 × (weight ÷ hp)^⅓, with weight in pounds. A 3,300 lb car with 300 hp estimates to about 12.9 seconds. It's an approximation — traction and gearing shift the real number.
How is trap speed calculated?
Trap speed (the speed at the end of the quarter mile) ≈ 234 × (hp ÷ weight)^⅓ in mph. Because it depends mainly on power-to-weight and less on the launch, trap speed is often a better guide to a car's power than ET.
Why is my real quarter-mile time different?
The formulas assume a good launch and traction. Wheelspin, tall gearing, a slipping clutch, high altitude or a heavy street car will all run slower than predicted; a sticky-tyred, well-tuned car can beat it. Treat the estimate as a starting point.
Should I use crank or wheel horsepower?
Either works as long as you're consistent, but the formulas were largely fitted to flywheel (crank) figures. Wheel horsepower is roughly 10–15% lower due to drivetrain loss, so using it gives a slightly more conservative estimate.
Does weight include the driver?
Yes — use the car's race weight with the driver and any fuel aboard, since that's what actually accelerates. Adding the driver (typically 70–90 kg) noticeably affects the result on a light car.