# Quarter Mile Calculator

URL: https://speedycalculator.com/calculators/physics/quarter-mile/
Last updated: 2026-10-30

> The quarter mile calculator estimates a car's quarter-mile elapsed time (ET) and trap speed from its weight and horsepower, using the Huntington, Fox or Hale drag-racing formulas.

## Inputs

- Equation
- Weight (with driver) (lb, kg, t, US ton)
- Power (hp, kW, W)

## Results

- Quarter-mile elapsed time
- Trap speed
- Power-to-weight ratio

## Formula

```
Huntington: ET = 6.290·(W/P)^(1/3), trap = 224·(P/W)^(1/3) · Fox: ET = 6.269·(W/P)^(1/3)
Hale: ET = 5.825·(W/P)^(1/3), trap = 234·(P/W)^(1/3)   (W in lb, P in hp, speed in mph)
```

## Explanation

Drag racers have long used empirical formulas linking power-to-weight ratio to quarter-mile performance. They are a quick way to estimate what an engine upgrade or weight reduction will do – or to estimate horsepower from a timeslip.

### How to use the Quarter Mile Calculator

- **Equation**
- **Weight (with driver)**
- **Power**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Choose a formula, then enter the race weight of the car with driver and the engine power at the flywheel. Traction, gearing and aerodynamics make real runs vary by a few tenths.

### Inputs explained

FieldWhat to enterEquationChoose one: Huntington, Fox, HaleWeight (with driver)Units: lb, kg, t, US tonPowerUnits: hp, kW, W

### Example values

How the main result changes when **Weight** changes and everything else stays at the example values above:

Weight (with driver) (lb)Quarter-mile elapsed time (s)1,75010.2882,62511.7763,50012.9614,37513.9625,25014.8377,00016.33

## Worked example

Inputs — Equation: Huntington; Weight (with driver): 3,500 lb; Power: 400 hp.

Results — **Quarter-mile elapsed time = 12.961 s**; Trap speed = 108.7 mph; Power-to-weight ratio = 114.286 hp per 1,000 lb.

## Key terms

- **Elapsed time (ET)**: Time to cover a quarter mile from a standing start.
- **Trap speed**: Speed at the finish line.

## FAQ

**How accurate are these formulas?**
Usually within a few tenths of a second for well-launched cars.

**Which formula should I use?**
Huntington and Fox suit typical street cars; Hale gives faster times.

**Can I estimate horsepower from my timeslip?**
Yes – rearranging gives hp = W·(trap/224)³.

**Why does weight matter so much?**
Acceleration depends on force divided by mass.


## Sources

- [Hot Rod Network – Quarter-mile estimation formulas](https://www.motortrend.com/how-to/)