The Problem:

“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 5 days of 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%.”

The Solution:

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!

Related Content

Webinars (watch for free now!):
Eliminate the Confusion – Deep Dive into Task Types and Effort Driven
Webinar: Digging Deeper – Learning More about Inactivating Tasks and Inserting a Repeatable Block of Tasks

Do’s and Don’ts: Using Hammock Tasks
Inactivate Tasks: The Best Way to Make Temporary Changes in Your Schedule