This stopping distance calculator finds the total distance to stop a vehicle, adding the reaction distance and the braking distance. Enter the speed, reaction time, and friction above.
Formula
Reaction distance = v × tr Braking distance = v² ÷ (2 × μ × g) Total = Reaction + Braking
Example
v = 25 m/s, tr = 1.5 s, μ = 0.7: reaction 37.5 m + braking 45.5 m = 83 m.
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Frequently Asked Questions
How do I calculate stopping distance?
Add the reaction distance (speed times reaction time) to the braking distance (speed squared over twice friction times g).
Why does stopping distance grow so fast with speed?
Because braking distance depends on speed squared, so doubling speed roughly quadruples the braking distance.
What friction value should I use?
About 0.7 for dry asphalt, lower for wet or icy roads, which greatly increases stopping distance.