Stopping Distance Calculator
Enter your speed, and choose the road surface. You get the thinking distance, the braking distance and the total in metres, feet and car lengths.
These are typical distances for a car in good condition. Your own stopping distance will be longer if you are tired, distracted, or your tyres and brakes are worn.
Worked examples
Town speed
30 mph, dry road
9.1 m thinking, 13.7 m braking, 22.9 m in all
The Highway Code rounds this to 9 + 14 = 23 metres.
Motorway speed
70 mph, dry road
21.3 m thinking, 74.7 m braking, 96 m in all
About 24 car lengths.
About Stopping Distance Calculator
A stopping distance calculator shows how far a car travels before it stops. The distance is the sum of two parts. The thinking distance is how far you travel while you notice a hazard and react, before you touch the brake. The braking distance is how far the car goes while it slows to a stop. The Highway Code, rule 126, gives typical figures: at 30 mph a total of 23 metres, and at 70 mph a total of 96 metres.
Enter any speed in mph or km/h and choose a dry road, a wet road or ice. The tool uses the same method as the Highway Code, with thinking distance in feet equal to the speed in mph and braking distance in feet equal to the speed squared divided by 20, and shows the answer in metres, feet and car lengths. The wet and ice results use the Highway Code advice that distances double in the wet and can grow up to ten times on ice, applied to the braking distance, so they are a guide only.
How to use Stopping Distance Calculator
- Enter your speed and choose mph or km/h.
- Choose the road surface.
- Read the thinking, braking and total distance.
- Compare with the Highway Code table.
Common uses
- Learning to drive and the theory test
- Understanding 20 mph zones
- Setting a following gap
- Teaching young drivers
Frequently asked questions
What is the stopping distance at 30 mph?
The Highway Code figure is 23 metres: 9 metres to think and 14 to brake. The tool gives 22.9 metres, which is 75 feet, or about 6 car lengths.
What is the stopping distance at 70 mph?
96 metres in all, 21 metres of thinking distance and 75 of braking distance, equal to 24 car lengths of 4 metres.
Why does speed matter so much?
Braking distance grows with the square of speed. Doubling from 30 to 60 mph makes the braking distance four times longer, from 14 to 55 metres.
How much longer is it in the wet?
The Highway Code says to at least double the gap in the wet. The tool doubles the braking distance, so at 30 mph the total goes from 23 to 37 metres.
Do these figures apply to my car?
They are typical for a car in good condition on a dry road with an alert driver. Worn tyres, poor brakes, a heavy load, a slope and tiredness all make them longer.