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Braking distance

Speed: Reaction distance:
m/s m
mi/h ft
Normal braking
Braking distance m ft
Stopping distance m ft
Emergency braking
Braking distance m ft
Stopping distance m ft


The results have been rounded to significant digits.

This converter uses the rule of thumb (v/10)2 to calculate the braking distance of a car in a normal braking and the rule [(v/10)2] / 2 for the braking distance in an emergeny braking. For the stopping distance the reaction distance (v/10)*3 must be added. In the equations the speed v has the unit km/h and the distances are given in m.
ATTENTION ! The length of the braking distance depends on many parameters like the quality of the tyres, the road conditions (moisture, snow, ice, ...), the weight of the vehicle and the properties of the brakes. All these differences are not considered in the rules of thumb. Therefore, the calculation may NOT be used to determine a real braking distance. It may only help to estimate how a higher speed lengthens the braking distance of your car.

Usage: Type the speed into a field top left with the corresponding unit. After a mouse click on any free space of the window or on the "calculate"-button the calculation is performed. Read the result. Vice versa, you may also type the length of a braking distance and calculate the corresponding speed.
Move the mouse over a unit or click on it to read its full name. For another calculation just type in the new value. You may also click on the "reset" button before.

Example: What is the brakong distance in an emergency braking with a speed of 160 km/h ? Type "160" into the field in front of "km/h" top left. After a mouse click on any free space of the window or on the "calculate" button you can read the result. You need a braking distance of 128 m. In addition, the reaktion distance is 48 m. Therefore, the stopping distance will be 176 m.

- Large and small numbers are written exponentially. As example 2.3e5 = 2.3⋅105 = 230000 or 4.5e-5 = 4.5⋅10-5 = 0.000045.
- There is no warranty for the conversion. Cactus2000 is not responsible for damage of any kind caused by wrong results.
- Please send an email if you have suggestions or if you would like to see more conversions to be included.

© Bernd Krüger, 17.11.2008

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