This question might be considered a duplicate. It is closely related to these:

- https://mathematica.stackexchange.com/q/2241/121
- https://mathematica.stackexchange.com/q/14152/121
- https://mathematica.stackexchange.com/q/22419/121
- https://mathematica.stackexchange.com/questions/7768/profiling-from-mathematica

However, one simple reading of this question that I do not believe is covered in the answers above is answered with this [Front End option][1]:

 SetOptions[$FrontEndSession, EvaluationCompletionAction -> "ShowTiming"]

This will print the total evaluation time for each cell as it completes in the lower left window margin:

![enter image description here][2]

To make the setting persistent between sessions use `$FrontEnd` in place of `$FrontEndSession`.

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**Update:** `"ShowTiming"` was already covered in Brett's answer to: 

- https://mathematica.stackexchange.com/questions/1722/does-absolutetiming-slow-the-evaluation-time


 [1]: http://reference.wolfram.com/mathematica/tutorial/OptionInspector.html
 [2]: https://i.sstatic.net/D7VZ7.png