# How to calculate execution variance?

Our Program Management office is interested in identifying tasks where the projected execution differs from the planned execution. MS Project's "Duration Variance" field calculates the difference between the baseline duration and the planned duration

( ( [Baseline Finish] - [Baseline start] ) - ( [Finish] - [Start]) )

That doesn't contain any information about the execution variance. *Aside: I know that I could simply ignore [Actual Start] / [Actual Finish], and treat the Baseline as Planned and the Start/Finish as the execution, but I've got legacy assumptions to deal with. *

I tried to build a custom field [Projected Duration] such that

``````  [Finish] - [Actual Start]
``````

I also tried

``````  ProjDateDiff([Actual Start],[Finish])
``````

Aside: I'm aware that I would need some error checking to deal with Actual Start = NA, but let's solve the simple problem first

Both of those are returning "0" duration for tasks with known values for both fields.

How do I calculate execution variance?

Duration variance calculates the delta between the baseline duration and ACTUAL duration. All variances--SV, CV, FV, VAC, DV, etc.--calculate the delta between baseline and actual. So, no custom calculation necessary.

You will likely need a custom calculation if you are trying to determine the delta between baseline duration and latest revised estimate (LRE) duration. I don't think there is a out-of-the-box calculation for that.

• I thought so too; but according to Microsoft, Duration variance is calculated against the "start/Finish" not against "Actual Start/Finish". As I said, the easy way would be to ignore the fields "Actual Start", "Actual Finish", and treat "start/Finish" as actuals. That requires building a case for management, and this question is part of that case.
– MCW
Commented Oct 30, 2012 at 12:49
• That's true. As you update actual start and finish, it changes start and finish. As you are progressing your project, it recalculates remaining work based on finished work such that it will "predict" future performance and end of project results. It uses the start and finish column to do this. However, when you plug in actual start and finish, it takes those values and places them into start and finish and runs its calculations! It works beautifully. Commented Oct 30, 2012 at 13:08
• I wish I didn't have to accept that answer, but it appears to represent the truth. (apart from that "works beautifully" thing - can't agree there). Thanks for clarifying that. I'll use that to build the case to change our standard procedures.
– MCW
Commented Oct 30, 2012 at 13:35
• I did snicker when I wrote that. MSProject and I do not get a long well, but it does have some correct functionality! :) Commented Oct 30, 2012 at 13:43