# Car Crash Calculator

Created by Luciano Mino
Last updated: Jul 24, 2022

Our car crash calculator will obtain the g-force acting on the passengers of a car during a collision.

This tool can work as a:

• Impact force calculator;
• G-force calculator;
• Stopping time calculator; and
• Deceleration calculator.

Keep reading while we explain how to calculate impact force on a car crash using the impact force equation!

## Impact force definition and equation

Before using the car crash calculator, we need to explain some definitions, for example, impact force.

The impact force is the total force exerted on an object during a collision.

Using the law of conservation of energy, we can easily obtain the impact force equation for any object or person inside a car during a collision.

### Impact force formula

The moment before the crash, the car possesses kinetic energy, which reduces to zero right after the collision. This energy difference is compensated by the work done by the impact force:

$F\times d = \frac{mv^{2}}{2}$

therefore:

$F_{avg}= \frac{mv^{2}}{2d}$

where:

• $F$ is the average impact force during the collision;
• $v$ is the car's speed;
• $m$ is the mass of the object; and
• $d$ is the stopping distance, the distance where the car slows down to zero.

We can rewrite this expression using the time of collision $t$, resulting in:

$F_{avg}= \frac{mv}{t}$

which relates to the impulse and momentum formula.

💡 You can see from both equations that in order to reduce the impact force, we should focus on increasing the time of the collision or increasing the distance (both are equivalent).

## How to calculate impact force using the car crash calculator

Our car crash calculator can estimate the average impact force suffered by a passenger on a moving vehicle during a crash.

Although there are a lot of parameters that either increase or reduce this impact force (type of vehicle, type of collision, etc.), we've added only one parameter to be as general as possible: the seat belt.

With that in mind, to calculate the impact force:

1. Select if the passenger has their seat belt or not. This option will increase the collision time (with a seat belt) or reduce it, increasing the impact force (without a seat belt).
2. Input the car's speed before the collision.
3. Input the passenger's weight.
4. The car crash calculator will output the average impact force, stopping time, and deceleration.
Luciano Mino
Before the crash
Seat belt
No seat belt
Car speed
mph
lb
Crash
Average impact force
lbf
Stopping time
ms
Deceleration
g
It feels like being pressed with a mass of
lb
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