Fixed Duration and effort driven Task in MS PROJECT 2013



My Blog Reader has a problem: “Just a question. When I assigned a task to Fixed Duration, WITH EFFORT DRIVEN I see that Project has calculated some of the resources to work 50% or 33%. How does that work then? I had a 5 days work, with 4 resources. So after calculating, they still work for 5 days, still with four resources but of course less work. Thing is, I get two of these resources working 100% and one with 50% and the other with 33%! I cannot, for the life of me, work out WHY WOULD PROJECT calculate that when ALL RESOURCES are 100%.”

I’ll show how to manage that in MS PROJECT 2013.

First of all the formula:


You should remember this formula for the rest of your life.

Now suppose that you have an effort driven Task with Fixed Duration! What does it mean? It means that no matter how many Resources will work on the Task, it should have fixed, and unchanged duration. On the other hand, effort driven means that if you add another resource to the Task, all Resources should work less hours.

First I’ll crate a brand new Task:


and I’ll make that Task Fixed Duration – Effort Driven:


Now, let’s say that on that Project I have four Resources:


For explanation I will use Task Usage View, and I’ll add Peak Field in this View:


I’ll also use Detail View:


Finally I’ll click on the lower part on the Screen, and I’ll go to the Format Tab:


OK! Setup is done!

For my First Example I’ll add all Resources (four of them) AT ONCE)!


after I click at OK button I’ll get:


Let’s go back to the formula. Because I’d added all resources at once, MS PROJECT interprets that like: All four resources must work full time!.

So Duration = 5 days, Units = 100%, and Work = 5 days (5 days * 8 hours) * 100% = 40 hours per Resource!

As you can see, peak Units and Unit are 100%!

Now I am going to delete those resources and then I’ll do next:

  1. Add John and Click OK button
  2. Add Mary and Click OK button
  3. Add Peter and Click OK button
  4. Add Paula and Click OK button

I’ll get:


When I add Resources (Mary, after John, Peter after Mary, and Paula after Peter), MS PROJECT works like: You need another resource to finish that Tasks, so because the Task is effort driven, other resource will work less hours per day.

First I added John. Formula was:

Duration = 5 days, Units = 100%, and Work = 5 days (5 days * 8 hours) * 100% = 40 hours for John! And for the Task to complete, 40 hours are enough!

After that I added other Resources, and MS PROJECT says: OK, John will split his work with others. So this 40 hours will be split between John, Mary; Peter, and Paula!

Now look, at the Peak field, not at Units field. Every Resource will work 25% of available time per day:

Duration = 5 days, Peak Units = 25%, and Work = 5 days (5 days * 8 hours) * 25% = 10 hours for John, Mary, Peter and Paula!

You can see this in the Task Usage View:


To conclude, always look at the Peak field.

Hope this helps!



About Nenad Trajkovski


14 Responses to Fixed Duration and effort driven Task in MS PROJECT 2013

  1. Igor Gorečan says:

    The question at the beginning of the post remains unanswered. As does the question reiterated in the comments section. The bottom line is: “Why aren’t they evenly matched …?” Perhaps it’s a bug in PS 2013?

    I’ve read:
    For this discussion, the following sections are relevant
    How do task types affect the schedule?
    How does effort-driven scheduling affect the schedule?

    Now, supposing that default settings are used for the working hours, calendar, etc.
    I create Task1 – fixed duration + effort driven. I create resources A, B, C, D.

    I set the duration to 10d, work to 160h.
    Then I add the resources (task sheet / resource names – checkboxes) – simultaneously A, B, C, D. I see the work is spread evenly – 40h each of the 4 resources.

    Now I remove the resources from the task (simultaneously). Because of this, PS reduces work to
    0h. (expected because of the task type). Then I set the work again to 160h. (I expect I would be again in the same state like before I assigned the resources in the previous steps). Then I assign the resources again – simultaneously A, B, C, D.

    Suddenly I see the work is not spread evenly. The sum really is 160h, but proportions differ. Repeating the same exercise, the results vary. Note – there is also a difference if you use the task sheet / resource names – checkboxes, or if you use the Assign Resources dialog box.


    • Nenad Trajkovski says:

      I see. That is a Bug from my point of View. If you use Task form for assign resources after you removed them, you will get correct result. Let me know if this helps

  2. MP says:

    Nice Job, Nedan… I am a fresh new Project Manager (just started this month) – I was an IT Auditor before. Senior Management/Executives are asking for how much time each one of my project resources worked. I found that challenging from Project Office 2013 perspective, so I’ve located your site with the work task details. I look forward to get to my work today and brainstorm some more referring to your details. Your time is very appreciated!! Greetings from Phoenix, Arizona. MP

  3. Lvis says:

    Sorry the next part is wrong:
    It’s more that I don’t understand why the units don’t reflect the work

    See my earlier question for what I mean with the units.
    Sorry for the mess!

  4. Lvis says:

    Hi Nenad,

    I would like to response but your email-address gets rejected, so I will paste my answer to you here (the graphic will probably fail 🙂

    Hi Nenad,

    First of all, thank you very much for your response and patience!

    There is nothing special really that I want to achieve.
    It’s more that I don’t understand why the units don’t reflect the work:

    Inline afbeelding 1

    It seems that it has to do with some decisions MS made from 2007 to 2010 and that you have to rely on the Peak field.

    I would have found it more intuitive if that would show 25% as well!


  5. Lvis says:

    Hi Nenad,

    Very nice explanation!
    However I am banging my head against why after you added them one by one UNITS are shown like this:

    John 100%
    Mary 100%
    Peter 50%
    Paula 33%

    Why aren’t they evenly matched on 25% as well?

    Kind regards,

    • Nenad Trajkovski says:

      Can you be more specific. What do you want to achieve? What kind of Task do you have, etc…
      My mail is

  6. Bob says:

    This is very good information thank you. I do have a question on a type of task that I have not found an answer to. Let me give you two scenarios:
    1. You have a charter that needs executive sign off. You cannot proceed with the project until that sign-off occurs. You also know it will take at least a week to get the exec to sign off. But the actual “effort” is maybe 15 min. I need to keep the week because it is a critical path item. but then you have resource over allocation issues unless you set the % for the resource
    2. You have a task – “form Xfunctional team. This task, again on the critical path, will take you 18 days by the time you get all the sign-offs agreements etc. You actually only work on it for 15 min a day but need the duration of 3weeks to remain. If you put in 18 days for a resource you will get over allocation unless you set the % for the resource.

    Here is the basic question: If you have a task that is that is of a great duration but only will take a small amount of work is there a way to figure out:
    the % of work a person should be allocated automatically
    Or is there a better way to approach this rather than set the % of work?

  7. Hobbits House says:

    Thank you for the thorough explanation. Very helpful.

  8. Johan van Wyk says:

    Thanks for this infromation. I have a different problem. In an LOE task, we set Fix Duration, Turn off “Effort Driven” and set two constraints: Must finish on and Must start on. The problem is when resources does not enter time, when the task was suppose to start, MS project will move the date. That is not what we want. We want the task duration and dates to be constant and overallocations take place. THIS DOES NOT HAPPEN.

    Do you have any ideas on LOE tasks?

    • Nenad Trajkovski says:

      I do not understand the problem! Can you send me mpp file to, and give me a notice whith which Tasks do you have a Problem!

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