Braking Distance Calculator
Calculate total stopping distance based on speed, road conditions, and reaction time.
Supports both metric and imperial units.
Stopping Distance
Stopping distance is the total distance to come to a complete stop, combining reaction distance and braking distance.
Total Stopping Distance = Reaction Distance + Braking Distance
In metric (km/h, meters):
Reaction Distance (m) = Speed (km/h) / 3.6 × Reaction Time (s)Braking Distance (m) = Speed² / (2 × g × friction)- where Speed is in m/s and g = 9.81 m/s²
In imperial (mph, feet):
Reaction Distance (ft) = Speed (mph) × 1.467 × Reaction Time (s)Braking Distance (ft) = Speed² / (2 × g × friction)- where Speed is in ft/s and g = 32.17 ft/s²
Friction coefficients by road condition:
- Dry road: 0.7–0.8
- Wet road: 0.4–0.5
- Ice/snow: 0.1–0.2
Typical reaction times:
- Alert driver: 0.75–1.0 seconds
- Average driver: 1.0–1.5 seconds
- Distracted driver: 1.5–2.5+ seconds
Example at 100 km/h (62 mph) on dry road:
- Reaction distance: ~28m (1s reaction)
- Braking distance: ~56m
- Total: ~84m (276 ft)