Car Crash Force Calculator

What Is Car Crash Impact Force?

Impact force is the average force exerted on a vehicle and its occupants during a collision. By conservation of energy, the kinetic energy before the crash must be dissipated over the stopping distance. Longer crumple zones and seat belts spread that deceleration over more time and distance, reducing peak force.

Impact Force Formula

\(m\) is mass in kilograms, \(v\) is initial speed in meters per second, and \(d\) is stopping distance in meters. Deceleration follows from \(a = v^2/(2d)\), and kinetic energy is \(KE = \frac{1}{2}mv^2\).

Example: a 1,500 kg car at 50 km/h (13.89 m/s) stopping in 0.5 m produces \(F = 1500 \times 13.89^2 / (2 \times 0.5) \approx 289\) kN, roughly 29 tonnes of equivalent weight on the occupants.

Why Stopping Distance Matters

Seat belts, airbags, and crumple zones increase effective stopping distance from a few centimeters to tens of centimeters. Doubling stopping distance halves the average impact force. Divide deceleration by \(g = 9.81\,\text{m/s}^2\) to express the result in g-forces.