What stopping distance includes
Total stopping distance is the sum of two parts: the reaction distance traveled before the brakes are applied, and the braking distance traveled while decelerating to a stop.
The formulas used
Reaction distance is speed multiplied by reaction time. Braking distance uses v²/(2μg), derived from the work-energy relationship between kinetic energy and the friction force between tires and road, where μ is the road/tire friction coefficient and g is gravitational acceleration.
Actual stopping distances vary with tire condition, road surface, vehicle weight, and braking system, so treat results as estimates for general planning and educational purposes, not a substitute for safe following distances.
Last reviewed August 2026