Calculating braking distance – how it’s done?

Especially novice drivers must first develop a feeling for driving and learn to adapt their speed to the given driving situation. This also includes the correct estimation of the braking distance. But how long does it take a car to come to a stop?? And what is a simple way to calculate the braking distance?? Our car experts give the answer.

Without much effort – it’s so easy to calculate the braking distance!

It can be particularly helpful for new drivers who have little experience in assessing dangerous situations to visualize the braking distance while driving. After all, it is important for driving safety to know approximately how long a car takes to come to a stop. This also helps you to know how much distance you need to keep from the vehicle in front of you. Around the braking distance, there is a simple formula: To do this, read the current speed on the speedometer and divide it by ten. The resulting value is then multiplied by two to obtain the length of the braking distance. The rule of thumb for the braking distance is therefore:

Braking distance = (speed in km/h ÷ 10)²

If you want to calculate the braking distance from 120 km/h, take one tenth of the current speedometer reading and multiply the sum by itself. At a speed of 120 km/h, the braking distance during a normal braking process is thus mathematically 144 meters:

Braking distance = (120 ÷ 10) x (120 ÷ 10) = 12 x 12 = 144

To calculate the braking distance during a hazard braking, divide this value by two. In an emergency braking maneuver at 120 km/h, the car comes to a halt after about 72 meters.

What does the braking distance depend on??

But you should keep in mind that braking distance can vary greatly depending on the type of vehicle, weather conditions, road conditions, as well as the fitness of the driver. The actual braking distance therefore depends on a large number of factors and in practice can be lower or significantly higher than the calculated value. Normally, the braking distance of a car with ABS and on dry roads will be much smaller than the braking distance formula gives out. On the other hand, it can already be noticeably longer on wet roads and with worn tires. For a drive on snow and black ice, however, the calculated value no longer provides a reliable reference, because as our following example and the table illustrate, the actual braking distance is significantly higher than the calculated distance.

If you want to calculate the braking distance from 50 km/h, for example, the braking distance formula gives a value of 25 meters (50÷10)². In practice, the braking distance for a modern vehicle with ABS on a dry road is around half this value. So there is a sufficient safety cushion here, if you follow the rule of thumb. On wet roads, however, the actual stopping distance increases to around 20 meters, assuming minimum tire tread depth and an intact braking system. In snow and black ice, however, the actual braking distance is far outside the calculated value due to the enormous deceleration. It can then take more than 90 meters for the vehicle to come to a standstill. In this case, drivers should adjust their speed to the weather conditions, increase the safety distance and drive with particular caution. In addition, you should regularly have the braking system and tires of your car checked.

Stopping distance decisive!

What many drivers do not know: The braking distance only includes the distance covered from the moment the brake pedal is depressed until the vehicle comes to a standstill. The braking distance should therefore not be confused with the stopping distance. The stopping distance includes the entire braking process, which extends from detection of the obstacle to the standstill of the vehicle and is correspondingly significantly longer. It includes the reaction time (approximately 1 second) as well as other parameters such as the transfer distance (placing the foot on the brake pedal), the response distance of the brake (brake pressure build-up) and the threshold distance (locking of the wheels).

Speed Dry braking distance Wet braking distance Snow braking distance Ice braking distance Reaction distance in km/h in meters (m) in m in m in m
30 4,34 6,94 17,36 34,72 8,33
40 7,72 12,35 30,86 61,73 11,11
50 12,06 19,29 48,23 96,45 13,89
60 17,36 27,36 69,44 138,89 16,66
70 23,63 37,81 94,52 189,04 19,44
80 30,86 49,38 123,64 246,91 22,22
90 39,06 62,50 156,25 312,50 25,00
100 48,23 77,16 192,90 385,80 27,77
110 58,35 93,36 233,41 466,82 30,55
120 69,44 111,11 277,78 555,56 33,33
130 81,50 130,40 326,00 652,01 36,11
140 94,52 151,23 378,09 756,17 38,88
150 108,51 173,61 434,03 868,06 41,66
160 123,46 197,53 493,83 987,65 44,44

Table: Approximate braking distance calculated according to speed and road surface conditions. The values depend on the tire quality as well as the respective surface and the respective degree of wetness of the road (Source: ADAC).

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