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Eliminate the Confusion: Understanding the Peak Field

The 2010 version of Microsoft Project introduced some new functionality whose behavior has confused and confounded users with all degrees of experience, from absolute beginners to power users. Microsoft introduced this new functionality to fix a bug that had been present in the software since I first started using it many years ago. When Microsoft released Project 2010 in beta form, I confirmed that they did fix the bug, but I noted that new behavior in the software would probably confuse people. Of course, my prediction was absolutely correct!

This confusing functionality is how Microsoft Project responds when it needs to recalculate the Units value for resources assigned to a task. You see this confusing behavior in two specific situations:

  • You initially assign a resource to a Fixed Duration At a later time, you adjust the Work value for the resource, which means that Microsoft Project must recalculate the Units value for the resource.
  • You initially assign a resource to a Fixed Work At a later time, you adjust the Duration value for the task, which means that Microsoft Project must recalculate the Units value for the resource.

For example, notice in the Task Form view shown in Figure 1 that I assigned Mickey Cobb on a Fixed Duration task with a Units value of 50% and with a Duration value of 10 days. Notice that the software calculated a Work value of 40 hours for her on the task, as expected.

Figure 1: Resource assigned to a Fixed Duration task


Because the task is Fixed Duration, the Duration value is fixed or “locked” so that the value will not change. If I change the Work value to 60 hours, Microsoft Project must recalculate the Units value because it is the only remaining non-fixed variable. However, notice in Figure 2 that the software did not recalculate the Units value as expected! What is going on here? Is this a bug? No, it is not a bug. It is a consequence of the new functionality introduced back in Microsoft Project 2010.

Figure 2: Units value is not recalculated as expected


To implement this new functionality, the software development team for Microsoft Project 2010 created two new assignment fields in the software: the Assignment Units field and the Peak field. Because these two fields are assignment fields, you can only see them in the Task Usage view and the Resource Usage view. Neither of these fields are included in the default layout of these two views, so you must insert these fields manually if you want to see them and use them.

Figure 3 shows the Task Usage view with the Assignment Units and Peak fields inserted in the view. Notice that the Assignment Units field for Mickey Cobb displays the original Units value of 50%. Notice that the Peak field displays the new calculated Units value of 75%. To confirm that Mickey Cobb is correctly scheduled to work at a Units value of 75%, notice that the timephased grid on the right shows that she is assigned to work 6 hour per day for each day of the task schedule.

Figure 3: Assignment Units and Peak fields


I mentioned several times that this new functionality was introduced initially in the 2010 version of Microsoft Project, but you should know that this functionality is present in every other version of the software, including the 2013, 2016, and 2019 versions. When you see this confusing behavior in any of the last four versions of the software, keep in mind that what you are seeing is not a bug. The behavior is by design and cannot be changed, even if the design can be confusing.


Written by Dale Howard

Dale Howard is the Director of Education for PROJILITY. He has used Microsoft Project since version 4.0 for Windows 95 and he has used the Microsoft PPM tool since the first version of released as Project Central in the year 2000. He is the co-author of 21 books on Microsoft Project, Project Server, and Project Online. He is currently one of only 28 Microsoft Project MVPs in the entire world and one of only 6 in the United States.

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  1. Thanks for explanation.

  2. Thanks Dale – have been very aware of this “fix” since the 2010 release and have never understood what “new functionality” was actually added to cause this change. You mention it as well but it’s still not clear…and what bug did they fix that caused this change? I wasn’t aware of the Peak field so thanks again for sharing.

  3. Steve M —

    The new functionality is what I describe in the article. Prior to Microsoft Project 2010, the software would automatically recalculate the Units value and display the new value in the Task Form pane. The new functionality is that the new calculated Units value is not displayed in the Task Form pane, and instead is displayed in the Peak field, visible only in the Task Usage and Resource Usage views.

    The bug that was fixed was something that occurred rarely, but its behavior was bothersome. Suppose that you assign a resource to work full-time (Units value of 100%) on a task with 40 hours of Work. Suppose that the task was scheduled to start on Monday and that your organization is using the Timesheet functionality of either Project Server or Project Online. Suppose that on the first four days of the task, the team member reported 28 hours of Actual Work. Suppose that on Friday, the team member entered 12 hours of Actual Work on their timesheet. And suppose that the team member adjusts the Remaining Work value from 0h to 24h.

    The last step is where the bug comes into play. In all versions previous to the 2010 version, Microsoft Project would change the Units value to 150%, based on the 12h entered on Friday which completed the original 40h of assigned work. And then based on the new Units value of 150%, the software would schedule the 24 of Remaining Work at 12h per day and not 8h per day as expected.

    That’s the bug, and it was fixed in the 2010 version of Microsoft Project, but in it wake, it has caused confusion. Hope this helps.

    — eDale


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