Quarter Mile ET Calculator
The quarter-mile elapsed time (ET) calculator estimates how long it will take a vehicle to complete a quarter-mile (1,320 ft) drag race from a standing start. The formula ET = 6.290 * (weight / hp)^(1/3) uses the vehicle's total weight in pounds and wheel horsepower to produce an estimated elapsed time in seconds. This formula was developed from real-world drag strip data and is accurate for typical production-based vehicles on a prepped surface. It is widely used by performance enthusiasts and engine builders to predict the effect of power and weight changes before making expensive modifications.
Quarter-mile ET formula
ET (seconds) = 6.290 * (Vehicle Weight (lb) / Wheel HP)^(1/3)
This is an empirical formula derived from drag racing timing data. The constant 6.290 applies to a typical car on a prepped drag strip with radial tires. Some tuners adjust the constant slightly (6.0 to 6.5) to account for specific traction and aerodynamic conditions.
What affects quarter-mile performance?
- Power-to-weight ratio is the dominant factor. Doubling power while halving weight (same ratio) gives the same ET improvement.
- Traction: all the power in the world is worthless without grip. Drag radials and slicks can improve ET by 0.5-1.5 seconds over street tires on a high-power car.
- Reaction time: the 60-foot time is often the biggest variable separating good runs. Better launches reduce ET more than extra power on marginal traction tracks.
- Altitude and temperature: thinner air reduces power output. Expect slower times at high altitude or on hot, humid days.
Frequently asked questions
What is the ET formula?
The standard elapsed time (ET) estimate is ET = 6.290 * (weight / hp)^(1/3), where weight is the total vehicle weight in pounds and hp is the horsepower at the wheels. The constant 6.290 was derived empirically from drag racing timing data.
Is this formula accurate for all vehicles?
It works best for conventional rear-wheel drive cars with radial tires on a prepared track. Vehicles with exceptional traction (drag slicks, AWD), very high power levels, or significant aerodynamic drag may see 5-15% deviation from the estimate.
What is a good quarter-mile time?
A typical stock family sedan runs 15-17 seconds. A stock sports car runs 13-15 seconds. Quick street cars run 11-13 seconds. Competitive bracket racers run 10-12 seconds. NHRA Top Fuel cars run under 3.7 seconds.
How does weight reduction affect ET?
Since ET scales with (weight/hp)^(1/3), reducing weight 10% while holding HP constant improves ET by about 3.3%. Adding the same 10% in horsepower gives the same improvement. But weight reduction also improves traction loading and handling.
Should I use flywheel or wheel horsepower?
The formula is calibrated for wheel horsepower (WHP), the power actually reaching the ground. If you only have a flywheel HP figure, multiply by 0.85 (RWD) or 0.80 (AWD) to estimate WHP before entering it.
Official sources
- SAE International: sae.org - vehicle performance and powertrain standards.
- NHTSA: nhtsa.gov - vehicle weight ratings and safety data.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.