Highway Code stopping distances
These are the typical stopping distances for a car on a dry road, from rule 126 of the Highway Code. One average car length is taken as 4 metres.
| Speed | Thinking distance | Braking distance | Total | Car lengths |
|---|---|---|---|---|
| 20 mph | 6 m | 6 m | 12 m (40 ft) | 3 |
| 30 mph | 9 m | 14 m | 23 m (75 ft) | 6 |
| 40 mph | 12 m | 24 m | 36 m (118 ft) | 9 |
| 50 mph | 15 m | 38 m | 53 m (175 ft) | 13 |
| 60 mph | 18 m | 55 m | 73 m (240 ft) | 18 |
| 70 mph | 21 m | 75 m | 96 m (315 ft) | 24 |
How to work out stopping distances
The Highway Code figures follow two simple rules, which is how many people learn them for the theory test:
Thinking distance (feet) = speed in mph
Braking distance (feet) = speed² ÷ 20
1 foot = 0.3048 metres
At 50mph: thinking 50ft (15m), braking 50 × 50 ÷ 20 = 125ft (38m), total 175ft or about 53m. In metres, a handy shortcut is thinking = speed × 0.3 and braking = speed² × 0.015.
Why speed matters so much
Thinking distance rises in step with speed, but braking distance rises with the square of speed. Going from 30mph to 40mph is a third faster, but the braking distance goes up by about 70%. In the time a driver at 30mph has stopped, a driver who was doing 40mph is still travelling at around 30mph.
Wet and icy roads
The Highway Code says stopping distances will be at least double in the wet, and can be ten times greater on ice. Worn tyres, a heavier load and poor brakes all add to them. This is why the two-second rule becomes a four-second gap in rain.
Sources
- The Highway Code, rule 126: stopping distances
- The Highway Code, rules 227 to 237: driving in adverse weather
Rates and rules last checked 15 October 2026. These figures are a guide. For a decision that matters, confirm with the official source.