FREE CALCULATOR
How far until you stop?
Pick a speed and see your reaction distance, braking distance and stopping distance — worked out with the rules of thumb from the German theory test and drawn to scale.
- × 3reaction distance
- × itselfbraking distance
- ÷ 2emergency braking
- Reaction distance15 m
- Braking distance25 m
- Reaction distance
(50 ÷ 10) × 3 = 15 m - Braking distance
(50 ÷ 10) × (50 ÷ 10) = 5 × 5 = 25 m - Stopping distance
15 m + 25 m = 40 m
- Half the speedometer (outside towns)25 m
- 2 seconds (outside towns)27.8 m
- 1 second (in town, minimum)13.9 m
At 100 km/h — double the speed — the braking distance is 100 m: four times as long.
How it works
Reaction distance is how far the car travels in the second before you brake. Rule of thumb: speed divided by 10, times 3.
Braking distance grows with the square of the speed: speed divided by 10, multiplied by itself. In an emergency stop it is about half as long.
Stopping distance = reaction distance + braking distance. The exam uses these rules of thumb; real distances depend on your reaction, tyres, brakes and the road.
Questions and answers
How do you calculate stopping distance?
Add reaction distance and braking distance. At 50 km/h: (50 ÷ 10) × 3 = 15 m reaction distance, (50 ÷ 10) × (50 ÷ 10) = 25 m braking distance, 40 m stopping distance.
What changes in an emergency stop?
The braking distance is about half as long: at 50 km/h 12.5 m instead of 25 m, so the stopping distance is 27.5 m.
Why is double the speed so dangerous?
Braking distance grows with the square of the speed: at twice the speed it is four times as long.
How much distance should I keep to the car in front?
Outside towns, a rule of thumb is half the speedometer in metres (40 m at 80 km/h) or two seconds. In town, at least one second.
Sources
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