Calculator
Quarter Mile Calculator
Estimate a car's 1/4-mile time, trap speed and 1/8-mile time from its weight and horsepower using the classic power-to-weight drag racing formulas.
A 12.0-second quarter-mile car, crossing the line at about 182 km/h (113 mph).
How the estimate works
Drag racers have long predicted quarter-mile results from power-to-weight alone. This calculator uses the widely used empirical formulas:
- Elapsed time (s) = 5.825 × (weight in lb ÷ hp)1/3
- Trap speed (mph) = 234 × (hp ÷ weight in lb)1/3
Trap speed tracks power-to-weight closely because the car is already moving fast; elapsed time also depends on the launch. That is why the trap speed estimate is usually more accurate than the ET.
Why real cars run faster or slower
The formulas assume a well-hooked launch. All-wheel drive, launch control and quick-shifting dual-clutch gearboxes often beat the predicted ET; rear-wheel-drive cars on street tyres, front-wheel-drive cars and tall gearing are usually slower. Use crank (flywheel) power, not wheel power, and include the driver and fuel in the weight. Altitude and heat reduce the output of naturally aspirated engines by roughly 3% per 300 m (1,000 ft).
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