Microsoft Project 2013: A summary task shows a wrong total of DURATION HOURS: The sum should be 31 hours, but it shows only 25 hours. However, the sum of WORK HOURS is correct. Also, the calculation of costs is correct. So, somewhere, 6 hours just in the duration are missing.

  • The summary task has NO resources assigned.
  • The summary task has NO predecessor assigned.
  • All tasks below the summary task have the same resource, all at 100% capacity.
  • In the tasks below, work and duration are all equal, which is correct.

So what could be wrong ?


1 Answer 1


If each task has the same resource at 100% and the durations of the subtasks all equal the work, then the only possible explanation for a shorter summary duration is that one or more of the subtasks overlap, which would yield a resource over-allocation.

You can use the Resource Usage view to check this as it will be obvious which tasks are causing the over-allocation and resolve by moving tasks/levelling resources.

  • 1
    Thanks, exactly that was the issue. I resolved the resource over-allocation, and now it works.
    – user16911
    Commented Apr 21, 2015 at 14:53

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