I've got a strange issue in my mpp. I've got one task which was originally estimated to take 20hrs which I scheduled over 15 days (resource only available 30% of the time). Looking at the dates I noticed that the task was starting in early August and ending late October, obviously beyond the 15 days.

I changed it around to test and when the task was estimate of 1hr duration, it still started early August and finished late Sept... Definitely something wrong

What I have checked and is not wrong:

  • Project working week is as expected - 8 - 5, monday to friday, no mass holidays
  • No resource holidays over the period
  • No percentage of complete entered
  • Automatically scheduled
  • Predecessors and Successors not showing same problem

However other tasks in the mpp are having similar problems around the same dates, so I'm sure it must be a calendar issue but I'm not sure where to look.

Problem is this affects my whole timeline now.

Please advise what I should look into,


  • Open the gantt chart and see if your tasks are split. Duration and time passed are not the same thing. Commented Sep 6, 2016 at 11:38
  • What are your project settings for hours per day and days per week?
    – Rubén
    Commented Sep 10, 2016 at 22:12

3 Answers 3


SeekWisdom is correct. You need to use work vs. duration to determine the dates. You will need to right click in the Heading line and add the field Work. Duration will auto calculate the work divided by your resources Working Time to sum the days (or hours depending on your calculation choice).


Considering the basis of your question as your requirement: 20 hours’ work required for a task, over 15 days duration with 30% resource allocation.

30% of a single day is 2.4 hours, times 15 days = 36 hours and not 20 hours.

There is a mismatch in your requirement between the 20 hours of work vs. 36 hours of work yielded from the 30% allocation.

You will need to 'freeze' some combination of your Duration, Work, % Resource Allocation and allow the other to ‘float’ in the calculation process. Here are some options below:

  • Freeze 15 days and 20 hours total work: either 16% or 17% resource allocation (running tests on MS Project 2010 standard; does not handle fractional % allocations – comes up with 17%)

  • Freeze 30% allocation and 15 days: 36 hours work

  • Freeze 30% allocation and 20 hours: 8.33 days duration

You can allow MS Project to perform the desired calculation by adjusting your Task type or 'fixed-ness’ by choosing the desired task and performing the following:

Task Information ==> Advanced tab ==> Task Type drop down Then choose between - Fixed Units - Fixed Duration - Fixed Work

An additional consideration is the effort driven check box, also on the advanced task. This mostly comes into play when you have more than one resource on a task, which did not seem to be a part of your requirement and question. From the Microsoft website at the second link below:

“When you assign or remove people from a task, Project lengthens or shortens the duration of the task based on the number of resources that are assigned to it, but Project does not change the total work for the task. This is called effort-driven scheduling and is the setting Project typically uses when you assign resources to tasks.”

Additional information

Task Types: https://support.office.com/en-US/article/Change-the-task-type-for-more-accurate-scheduling-B0B969AD-45BC-4E9E-8967-435587548A72

Effort Driven checkbox https://support.office.com/en-US/article/Change-the-effort-driven-setting-for-task-types-18EFD7C7-D146-4B06-BDBE-B6A11564BDF3

Good Luck


Switch to "Task Usage" and "Resource Usage" views and check the expected work hours per day, during the problematic periods. You can see if there are specific dates with non-working time or unavailable resources.

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