# Stopping Distance Calculator

URL: https://speedycalculator.com/calculators/physics/stopping-distance/
Last updated: 2026-10-25

> The stopping distance calculator estimates how far a vehicle travels before stopping: the reaction distance during the driver’s reaction time plus the braking distance on the road surface.

## Inputs

- Speed (km/h, mph, m/s)
- Reaction time (s)
- Road condition

## Results

- Reaction distance
- Braking distance
- Total stopping distance

## Formula

```
Reaction distance = v × t
Braking distance = v² ÷ (2 μ g)
```

## Explanation

Stopping distance rises with the square of speed, so going a little faster adds a lot of distance, especially on wet roads.

### How to use the Stopping Distance Calculator

- **Speed**
- **Reaction time**
- **Road condition**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Speed times reaction time gives the reaction distance. Braking distance uses the friction coefficient between tyres and road.

### Inputs explained

FieldWhat to enterSpeedUnits: km/h, mph, m/sReaction timeIn sRoad conditionChoose one: Dry asphalt (μ ≈ 0.7), Wet asphalt (0.4), Gravel (0.35), Snow (0.2) …

### What each result means

- **Reaction distance** = [Speed] × [Reaction time]
- **Braking distance** = [Speed]^2 ÷ (2×[Road condition]×g)
- **Total stopping distance** = [Reaction distance] + [Braking distance]

### Example values

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

Speed (km/h)Total stopping distance (m)2513.9337.523.535034.8862.5487562.8610097.87

## Worked example

Inputs — Speed: 50 km/h; Reaction time: 1.5 s; Road condition: Dry asphalt (μ ≈ 0.7).

Results — Reaction distance = 20.83 m; Braking distance = 14.05 m; **Total stopping distance = 34.88 m**.

## FAQ

**How much does speed matter?**
Doubling speed roughly quadruples braking distance.

**What reaction time should I use?**
1–1.5 s is typical for an alert driver; fatigue and phones increase it.

**What formula does the Stopping Distance Calculator use?**
Reaction distance = v × t.