Stopping Distance Calculator
Calculate total stopping distance at any speed — reaction distance plus braking distance — for dry, wet or icy roads.
How to use
- 1Enter the speed and choose the road condition.
- 2Adjust reaction time if needed (1.5 s is a common planning value).
How it's calculated
Reaction distance = speed × reaction time. Braking distance = v² ÷ (2 × μ × g), with friction μ ≈ 0.7 dry, 0.4 wet, 0.1 icy.
Frequently asked questions
Why does speed matter so much?
Braking distance grows with the square of speed — doubling your speed quadruples the braking distance.
What's a safe following distance?
At least a 2-second gap in good conditions (3–4 seconds recommended in the US), double in the wet and much more on ice.
How accurate is this?
It's an estimate — tyres, brakes, road surface, slope and vehicle load all change real stopping distances.