The rate of change in velocity is the acceleration. The change in velocity of an object divided by the time period is called as its average acceleration. This is an online calculator to find the average acceleration with the given values.
Consider the initial and final velocities to be 5,7 and initial and final time 2,3.
Step 1 : 7-5 / 3-2
Step 2 : 2 / 1 = 2
Hence the average acceleration is 2.