Deceleration Distance Calculator - Stopping Distance & Time

Calculate deceleration distance from initial speed and braking rate, or find the deceleration rate from speed and distance or braking time.

Related Calculators

Deceleration Distance Formula

The following constant-deceleration formula calculates distance to a final speed. Use final speed 0 for a complete stop:

d = (vi² - vf²) / (2 \times a)

Variables:

d is the deceleration distance (meters)
vi is the initial speed and vf is the final speed (meters per second)
a is the deceleration (meters per second squared)

Subtract the final speed squared from the initial speed squared, then divide by twice the positive deceleration. For a full stop, final speed is zero.

What is Deceleration Distance?

Deceleration distance is the distance required for a moving object to come to a complete stop when a constant deceleration is applied. It is a critical factor in vehicle safety and is used to design roadways, runways, and safety systems. This calculator is an idealized model and does not establish safe stopping performance, speed or following distance. Surface coefficients are illustrative assumptions, not measured road conditions.

How to Calculate Deceleration Distance?

The following steps outline how to calculate the Deceleration Distance.

First, enter the initial speed and choose its unit; enter the final speed or leave it blank for a full stop.
Next, determine the deceleration (a) in meters per second squared.
Next, use d = (vi² − vf²) / (2 × a); a friction estimate also accounts for the chosen grade.
Select Calculate to find distance in meters. Optional reaction time adds travel at the initial speed before braking; mass adds net force and kinetic-energy loss.
After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Initial speed (v) = 20 m/s

Deceleration (a) = 5 m/s²

Deceleration Distance Calculator screenshot