# Stopping distance calculator

URL: https://byshahid.com/tools/stopping-distance-calculator/
Author: Muhammad Shahid (https://byshahid.com/)
Free tool · runs in your browser

Work out how far a car travels before it stops at any speed, on a dry, wet or icy road, using the Highway Code figures.

**Quick answer:** Stopping distance is thinking distance + braking distance. The Highway Code gives 23 metres at 30 mph (9 m thinking + 14 m braking) and 96 metres at 70 mph (21 m + 75 m), about 24 car lengths. On a wet road the stopping distance is at least double; on ice the braking distance can be up to ten times longer. Enter any speed here to get the distance in metres, feet and car lengths.

## How to use it

1. **Enter your speed.** Type a speed or tap a preset, in mph or km/h.
2. **Choose the road.** Pick dry, wet or icy. Optionally enter your own reaction time.
3. **Read the distances.** See thinking, braking and total distance in metres, feet and car lengths, and the Highway Code chart below.

## Example

A car at 30 mph on a dry road, using the Highway Code figures:

Input:

```
Speed: 30 mph
Road: dry
```

Output:

```
Total stopping distance: 23 m
Thinking distance: 9 m
Braking distance: 14 m
In feet: 75 ft
In car lengths: 6 car lengths
```

## Common errors and how to fix them

- **My figure differs from the theory test chart**: Between the chart speeds the tool uses the formula behind it, and an own reaction time changes the thinking distance. Leave the reaction time empty and use 20, 30, 40, 50, 60 or 70 mph for the exact chart figures.
- **The wet road figure looks too high**: The Highway Code says at least double, so the tool doubles both thinking and braking distance. Real figures depend on tyres and the depth of water.

## Frequently asked questions

### What is the stopping distance at 30 mph?

23 metres (75 feet), about 6 car lengths: 9 metres of thinking distance and 14 metres of braking distance, according to the Highway Code.

### What is the stopping distance at 70 mph?

96 metres (315 feet), about 24 car lengths: 21 metres thinking and 75 metres braking. That is roughly the length of a football pitch.

### What are the stopping distances from 20 to 70 mph?

20 mph: 12 m. 30 mph: 23 m. 40 mph: 36 m. 50 mph: 53 m. 60 mph: 73 m. 70 mph: 96 m. These are the Highway Code typical figures for a dry road.

### How do you work out stopping distance?

Add the thinking distance to the braking distance. Thinking distance is about 0.3 metres per mph; braking distance is about 0.015 metres times the speed squared. So at 40 mph: 12 + 24 = 36 metres. For the square of a speed, the [scientific calculator](https://byshahid.com/tools/scientific-calculator/) helps.

### Why does braking distance grow faster than speed?

Braking distance depends on the square of the speed. Double your speed from 30 to 60 mph and the braking distance roughly quadruples, from 14 to 55 metres.

### How much longer is stopping distance in the wet?

The Highway Code says stopping distances will be at least double on wet roads, because tyres have less grip. At 30 mph that means at least 46 metres.

### How much longer is stopping distance on ice?

Braking distance can be up to ten times greater on ice, according to the Highway Code. At 30 mph that is up to 140 metres of braking alone.

### What is thinking distance?

The distance travelled between seeing a hazard and pressing the brake. The Highway Code figures assume about two thirds of a second. Tiredness, alcohol, drugs and phones make it longer.

### What is the two-second rule?

Leave at least a two-second gap to the vehicle in front on fast roads, and double it in the wet. The calculator shows how many metres two seconds is at your speed. To add up journey times, use the [time calculator](https://byshahid.com/tools/time-calculator/).

### How long is a car length?

The Highway Code chart counts a car length as about 4 metres. Car lengths are an easy way to picture the distance on the road.

### Are these figures on the UK theory test?

Yes. Theory test questions use the Highway Code stopping distances, so learn the 20 to 70 mph chart below. The RoadTick app has practice questions on them.

## Related

- [UK stopping distances: chart and how to remember them](https://byshahid.com/blog/stopping-distances-uk-theory-test/)
- [Time calculator](https://byshahid.com/tools/time-calculator/)
- [Percentage calculator](https://byshahid.com/tools/percentage-calculator/)

## Sources

- [The Highway Code: rule 126, stopping distances](https://www.gov.uk/guidance/the-highway-code/general-rules-techniques-and-advice-for-all-drivers-and-riders-103-to-158)
- [The Highway Code: rules 227 and 230, wet and icy roads](https://www.gov.uk/guidance/the-highway-code/driving-in-adverse-weather-conditions-226-to-237)