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Final Velocity Calculator

Find the final velocity of an accelerating object.

How it is calculated

The tool uses the first equation of motion for constant acceleration along a straight line:

v = u + a × t

Here u is the initial velocity in m/s, a is the acceleration in m/s² and t is the time in seconds. The answer is in m/s, rounded to two decimals. Negative values are allowed for u and a, so slowing down is entered as a negative acceleration. The tool does not stop the motion at zero: if the object would have halted and reversed, the result is simply negative. All three values are needed.

Worked example

A cart moves at u = 5 m/s and accelerates at a = 2.5 m/s² for t = 8 s. The speed gained is 2.5 × 8 = 20 m/s. Adding the starting speed gives v = 5 + 20 = 25.00 m/s. In the other direction, a car at 20 m/s braking at −4 m/s² for 8 s gets 20 + (−4 × 8) = −12.00 m/s, which signals that the formula has run past the moment it stopped (after 5 s).

Try this example →

Common mistakes

  • Entering braking as a positive acceleration; deceleration must be negative.
  • Mixing units, such as speed in km/h with time in seconds. Convert km/h to m/s by dividing by 3.6 first.
  • Applying the formula when acceleration is not constant (a car pressing and releasing the pedal); it is valid only for steady acceleration.
  • Not noticing a negative result after slowing down. It means the object would already have stopped and begun reversing, which is usually not the physical situation.
  • Entering the time in minutes while acceleration is per second squared.

About this calculator

This calculator applies the first kinematic equation of motion, v = u + at — final velocity equals initial velocity plus acceleration times time — for an object moving with constant acceleration in a straight line.

Physics students use it as the standard starting point for motion problems, from a car accelerating from a stoplight to an object in free fall, and it's the building block engineers use when modeling how quickly a vehicle, elevator, or projectile reaches a given speed under a known, constant acceleration.

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