Quarter-Mile ET & Trap Speed Estimator
Estimate quarter-mile elapsed time and trap speed from vehicle weight and horsepower. Includes 1/8 mile estimates.
Total vehicle weight with driver and fuel
Wheel horsepower for most accurate results
How These Estimates Work
This calculator uses the Brock/Huntington formula, which has been the standard drag racing estimation method for decades. It calculates ET and trap speed purely from the power-to-weight ratio.
ET = 5.825 × (Weight / HP)^(1/3)
Trap Speed = 234 × (HP / Weight)^(1/3)
Accuracy and Limitations
These formulas are typically within 0.5–1.0 seconds of real-world results for a well-hooked street car with a decent launch. However, they don't account for:
- Traction: The single biggest variable. A car that spins the tires will be much slower than predicted.
- Launch technique: A good 60-foot time can make or break an ET.
- Gearing: Poorly matched gear ratios can leave power on the table.
- Density altitude: Hot, humid, high-altitude air reduces power.
- Aerodynamics: Matters more at higher speeds.
- Drivetrain loss: Use wheel HP for better accuracy, not crank HP.
Trap Speed vs ET
Trap speed (the speed you cross the finish line at) is a better indicator of raw power than ET. ET is heavily influenced by the launch and 60-foot time, while trap speed reflects the car's average power output down the track. Two cars with the same trap speed have similar power — even if their ETs differ because one launched better.
1/8 Mile Estimates
The 1/8 mile values use standard conversion ratios from quarter-mile data. The 1/8 mile ET is roughly 63% of the quarter-mile ET, and the speed is roughly 81% of the trap speed. These are approximations.