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Stopping Distance Calculator
Estimate how far a vehicle travels before it stops. Enter your speed, a reaction time and the road surface to get the distance covered while you react, the braking distance, and the total.
- Reaction distance
- 132 ft
- Braking distance
- 171.92 ft
- Time to stop
- 5.41 s
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Formula
How to use it
- Enter your speed in mph or km/h.
- Enter a reaction time; 1.5 seconds is a reasonable everyday figure.
- Choose the road surface, or enter your own friction coefficient.
- Read the total and see how it splits between reacting and braking.
Worked examples
60 mph on dry asphalt with a 1.5 second reaction time
- Reaction distance
- 132 ft
- Braking distance
- 171.92 ft
- Total stopping distance
- 303.92 ft
- Time to stop
- 5.41 s
30 mph on a wet road with a 1.5 second reaction time
- Reaction distance
- 66 ft
- Braking distance
- 75.22 ft
- Total stopping distance
- 141.22 ft
- Time to stop
- 4.92 s
100 km/h on dry asphalt with a 1 second reaction time
- Reaction distance
- 91.13 ft
- Braking distance
- 184.39 ft
- Total stopping distance
- 275.52 ft
- Time to stop
- 5.05 s
Speed counts twice
Reaction distance grows in proportion to speed, but braking distance grows with the square of speed. Double your speed and the braking distance quadruples: on dry asphalt it is about 43 ft at 30 mph and about 172 ft at 60 mph.
At 60 mph you cover 88 ft every second, so each extra half second of reaction time — a glance at a phone — adds 44 ft before the brakes are even applied.
About the friction values
The surface options use typical tire-to-road friction coefficients: about 0.7 for dry asphalt, 0.4 for wet, 0.2 for packed snow and 0.1 for ice. Real values vary with tire condition, tread depth, road texture, temperature and whether the brakes lock, so a modern car with good tires may stop shorter on dry pavement and worn tires will stop longer in the wet.
These results are planning estimates for understanding and comparison, not a guarantee of how any vehicle will stop; they are not a substitute for official guidance, road design standards or a qualified professional’s analysis.
Questions people ask
What is the stopping distance at 60 mph?
About 304 ft on dry asphalt with a 1.5 second reaction time: 132 ft travelled while reacting plus 172 ft of braking.
How much longer does it take to stop on a wet road?
Braking distance on wet asphalt is roughly 75% longer than on dry, using friction of 0.4 instead of 0.7. At 60 mph braking takes about 301 ft instead of 172 ft.
What is the formula for braking distance?
Speed squared divided by (2 × friction coefficient × gravity). In mph and feet that is mph² ÷ (30 × friction). At 30 mph on a wet road: 900 ÷ 12 = 75 ft.