# Difference between Turn Around Time (TAT) and Waiting Time (WT) in CPU Scheduling

• Difficulty Level : Medium
• Last Updated : 04 Jul, 2022

In CPU Scheduling, we often need to find the average Turnaround and Waiting Time with the help of Arrival, Burst and Completion Time. Let’s have a brief look of them: Turnaround Time (TAT):

1. It is the time interval from the time of submission of a process to the time of the completion of the process.
2. The difference b/w Completion Time and Arrival Time is called Turnaround Time.

Completion Time (CT): This is the time when the process completes its execution. Arrival Time (AT): This is the time when the process has arrived in the ready state.

`TAT = CT - AT`

Waiting Time (WT):

1. The time spent by a process waiting in the ready queue for getting the CPU.
2. The time difference b/w Turnaround Time and Burst Time is called Waiting Time.

Burst Time (BT): This is the time required by the process for its execution.

`WT = TAT - BT`

Now with Waiting Time and Burst Time, we can also calculate Turn Around Time via:

`TAT = BT + WT`

Example:

Solution: Figure – Gantt Chart

```Avg. TAT = (24 + 27 + 31) / 3 = 27.33 sec
Avg. WT  = (0 + 24 + 27) / 3 = 17.0 sec ```

Let’s see the difference between Turnaround Time and Waiting Time:

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