Vehicle Stopping Distance Calculator
Calculate total stopping distance — reaction time + braking — at any speed and road surface.
What this calculates
Total stopping distance has two parts: thinking distance (you react) and braking distance (the car decelerates). At highway speeds, the braking portion dominates because it scales with velocity squared. Wet pavement and ice double or quadruple braking distance.
Formula & how it works
Thinking distance = speed × reaction_time. Braking distance = v² / (2 × μ × g), where v = m/s, μ = friction coefficient (0.7 dry asphalt, 0.4 wet, 0.15 snow, 0.10 ice), g = 9.81 m/s².
Worked example
60 mph (26.8 m/s), 1.5 s reaction, dry asphalt. Thinking: 40.3 m. Braking: 52.3 m. Total: 92.6 m (304 ft).
Frequently asked questions
Why squared?
Kinetic energy = ½mv². Doubling speed quadruples the energy that must be dissipated to stop.
Tire/brake condition?
Worn tires below 4/32" tread can double wet braking distance. Worn brake pads degrade more gradually.
ABS effect?
ABS prevents lock-up so you can steer while braking. Stopping distance is similar on dry pavement, slightly longer on gravel/snow.
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