Stopping Distance Calculator
Calculate total stopping distance from speed, reaction time and braking deceleration with this free driving safety calculator online.
Enter Values
Minimum 0
Minimum 0
How to use this calculator
- Enter the speed.
- Adjust reaction time and braking deceleration if needed.
How it works
Reaction distance = speed × reaction time; braking distance = speed² ÷ (2 × deceleration).
Worked example
60 km/h. ≈ 25 m reaction + 20 m braking = ~45 m.
Common mistakes
- Underestimating reaction time — 1.5 s is typical, fatigue makes it worse.
- Assuming dry grip — wet or gravel roads need much more distance.
Frequently asked questions
How is stopping distance calculated?
It adds reaction distance (speed × reaction time) to braking distance (speed² ÷ 2 × deceleration), so it climbs sharply with speed.
Why does stopping distance grow so fast with speed?
Braking distance depends on speed squared, so doubling your speed roughly quadruples the braking distance — a key reason small speed rises matter.
Why does speed matter so much?
Braking distance grows with the square of speed — doubling speed roughly quadruples the braking distance.
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Cite this tool
Zerdly. (2026). Stopping Distance Calculator. Retrieved from https://www.zerdly.com/tools/stopping-distance-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.