🏁 1/4-Mile ET & Trap Speed Calc
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 1/4-mile et & trap speed calc 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.