Drag racing performance estimator
1/4 Mile Calculator
Estimate quarter-mile elapsed time (ET) and finish-line trap speed from race weight and horsepower. Compare three empirical models and keep wheel versus crank power explicit.
Estimated quarter-mile performance
1/4 Mile ET
11.65 s
Trap Speed
117.0 mph
Calculated from 3200 lb race weight and 400 WHP.
Formula comparison
How to use the quarter-mile calculator
The calculator normalizes weight to pounds and power to wheel horsepower before applying the selected cube-root model.
1. Enter race weight
Use the total weight as raced: vehicle, driver, fuel, and carried equipment—not curb weight alone.
2. Identify the power basis
Use measured WHP when available. For crank power, state the drivetrain-loss assumption used to estimate WHP.
3. Compare the models
ET is launch-sensitive; trap speed is generally more power-sensitive. Treat both as estimates, not timing-slip predictions.
Formulas and constants
All three models use race weight in pounds and wheel horsepower. Their different constants produce meaningfully different results, so the calculator displays every model instead of hiding the choice.
| Model | Elapsed time (seconds) | Trap speed (mph) |
|---|---|---|
| Huntington | 6.290 × (weight / WHP)^(1/3) | 224 × (WHP / weight)^(1/3) |
| Fox | 6.269 × (weight / WHP)^(1/3) | 230 × (WHP / weight)^(1/3) |
| Hale | 5.825 × (weight / WHP)^(1/3) | 234 × (WHP / weight)^(1/3) |
What this model does not know
These first-order formulas do not directly model tire grip, launch technique, gearing, shift time, aerodynamics, density altitude, track preparation, or power delivery. A car can match the predicted trap speed while missing the predicted ET because the launch was different.
Input rules that prevent bad estimates
- • Include the driver, fuel, and race equipment in vehicle weight.
- • Do not mix wheel horsepower with manufacturer crank horsepower.
- • Match formula constants and input basis before comparing results from two sites.
Quarter-mile calculator FAQ
How accurate is a quarter-mile calculator?
It is a power-to-weight estimate. Accuracy depends on the quality of the inputs and how closely the vehicle's launch, traction, gearing, and conditions resemble the assumptions behind the formula.
Should I use curb weight or race weight?
Use race weight: the vehicle plus driver, fuel, and anything carried during the run. Using curb weight alone usually makes the estimate too optimistic.
Should I enter wheel or crank horsepower?
Wheel horsepower is the clearest input because it avoids a drivetrain conversion. If only crank horsepower is known, select flywheel power and state the loss assumption.
Why can ET be slow when trap speed looks right?
ET is strongly affected by the first part of the run. Wheelspin, a slow launch, and shift time can hurt ET while trap speed remains closer to the power-based estimate.