Calculating Elapsed Duration

I’ve been using so many of Microsoft Project’s approximately 900 functions for so long, that often times, I forget that some of the functions I take for granted are often undiscovered to long time users of the software.  In the last couple of months, at least twice, I’ve found end users to be unaware of the elapsed duration functionality.  Hence, I figured I’d write up a quick blog post about it.

Observing Elapsed Duration

First off, what is elapsed duration?  If you open Microsoft Project and enter “1ed” in the Duration column, you’ll see duration calculated as an elapsed day.


Essentially, it appears to be pretty much the same as a 1 day task.  Let’s calculate 7 elapsed days.


You’ll see that elapsed duration ignores the weekend non-working time and schedules the task over the weekend.

Now, let’s assign work resources to further illustrate the difference…


You’ll see that Task 1 is calculating per the normal duration calculation, i.e. 7 days X 8 hours per day = 56 hours.  Task 2 is actually calculating at 7 days X 24 hours per day = 168 hours.

Elapsed duration calculates a continuous 24 hour cycle and ignores non-working time.

Use Cases

So now we’ve defined elapsed duration.  When should we use this to model activities in our schedule?  Typically, you would use elapsed duration to model automated testing routines.  For instance, I might start a test on Friday at 5PM, and then let it run over the weekend.

Similarly, I might use elapsed duration to model tasks like data conversions.  I can kick the data conversion off before leaving for the day, then let the task run for 12 hours.  I am sure the potential uses are endless.

Last but not least, I know Dale Howard was recently noodling on a similar topic.  Check out his blog post for an overview of how to detect tasks using elapsed duration.

Calculating Elapsed Duration

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