Braking distance calculator
Calculate a car's stopping distance: the part covered during the reaction time and the braking part, on dry, wet, dirt or icy roads, with a table for several speeds.
How to useVehicle stopping distance
Light bar: reaction distance · dark bar: braking distance.
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Braking distance calculator: what it is for
Enter the speed, the reaction time and the road condition. The tool calculates the distance covered while the driver reacts, the braking distance with the formula v²/(2μg), the total stopping distance, the time to stop and how many car lengths fit in that space, plus a table from 30 to 120 km/h.
The calculations run in your browser and are estimates; always check your vehicle manual and local traffic laws.
How to use
- Enter the speed and reaction time.
- Choose the road condition.
- See the total distance and the table.
When to use it
- Understanding a safe following distance.
- Defensive driving lessons.
- Applied physics exercises.
Frequently asked questions
How is stopping distance calculated?
It is the sum of two parts. The reaction distance is the speed multiplied by the time the driver takes to hit the brake. The braking distance is v² / (2 · μ · g), where μ is the friction coefficient between tire and road and g is gravity.
What is a normal reaction time?
For an alert driver, 0.75 to 1.5 seconds. Fatigue, alcohol and phone use increase this time a lot, and the distance grows in the same proportion.
Why does doubling the speed quadruple the braking distance?
Because the car's energy grows with the square of its speed. At 100 km/h, braking takes about four times as long a distance as at 50 km/h. The values are estimates for tires and brakes in good condition; in practice the distance can be longer.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.