Project Management

Using a fixed duration task type in Microsoft Project

This Microsoft Project tutorial details how to use a fixed duration task type to schedule four hours of work over three days.
A colleague and I were discussing how Microsoft Project calculates duration, work, and resource utilization. My colleague was managing an outsourced project under a time and materials contract and wanted to schedule a four-hour task over three days. He had a few challenges trying to schedule the task in Microsoft Project until we discussed the importance of task types and the Duration X Units = Work equation.

Microsoft Project schedules tasks based on three variables: duration, units (or resources), and work. You get to choose two of these variables, and Microsoft Project calculates the third. Project managers run into a scheduling circle when they try to hold all three of these variables fixed. Just like the scope, cost, and time project triangle, if you change one variable, the others adjust as well.

In my colleague's scenario, the project manager has three days to complete four hours of work. Since the project is outsourced to a vendor, and the project manager doesn't have direct control of the resource, a fixed duration task type is recommended. The project manager doesn't care when the work gets done, as long as it's in the three day estimate. By setting the task to use a fixed duration task type, the number of hours and resources can fluctuate, and the three day duration will remain constant.

In actual practice using a time and materials contract, the project manager would care about the number of hours spent from a budget perspective. From a schedule perspective, the project manager is still expecting a three day fixed duration for the task.

Using the Duration X Units = Work formula, the project manager will enter duration and work into Microsoft Project and let the tool calculate resources.

To create a four-hour task using a three day fixed duration, follow these steps:

  1. Insert the Type and Work fields into the Gantt Chart view.
  2. Enter the task name.
  3. Change the Type field to Fixed Duration.
  4. Enter 3 days in the Duration column.
  5. Enter 4 hrs in the Work column.
  6. Assign a resource.
  7. Microsoft Project will calculate the 17% utilization.

Figure A depicts Task A using a three-day duration, four hours of work, and 17% resource utilization. Figure A

 

Figure A: three-day duration with four hours of work

In the Task B example, a Fixed Work task could be entered with a resource assigned 100%, and the resulting duration would be 0.5 days. Since the requirement is to complete the task within three days, the fixed duration task is recommended.

For internal projects with internal resource costs, I prefer to build fixed duration tasks using 100% allocated resources and let Microsoft Project calculate the work. For external projects that use different contract types, the mix of task types will depend upon the work and the level of tracking required in your project schedule.

To learn more about the different task types, read my Microsoft Project tutorial, Use Fixed Duration, Fixed Work and Fixed Unit Type Fields.

About

Dr. Andrew Makar is an IT program manager and is the author of How To Use Microsoft Project and Project Management Interview Questions Made Easy. For more project management advice visit http://www.tacticalprojectmanagement.com.

10 comments
mchadwick
mchadwick

Thanks for this as it clarified things a lot. However, one question I do need to clarify is when you say it calculates the resource utilization as 17%, does it? I have do this but the resource use for the task remains at 100%. I would also value comment on whether MS Project is really suitable for the work of my team. We normally work by scheduling duration but the work within it may only be for a fraction of that duration. Given the fact that MS Project does not seem to automatically calculate the resource unit percent (and clearly I do not want to calculate this manually) is it an effective tool to to manage things like resource over-allocation. It may of course be I am not setting things up correctly in which case i would LOVE some guidance

esnyder58
esnyder58

I'm using Project 2010 to get an idea for resource loading, knowing that the customer's dates are NOT going to change. It seems fixed duration is the right type to use for this, at least for this planning stage. At least in 2010, one must make sure the work is 0 before going through this drill. Decreasing the work DOES NOT recalculate the loading for the resource. To make changes, one must o Set the type to fixed duration o Set the hours to 0 o Clear the resource o Set the hours to the desired hours o Set the resource This will display the resource loading automatically.

koloor
koloor

The explanation given by Andy to use fixed duration task solved my probledm which was a puzzle for me for few days.

jnine
jnine

Does this work for longer than a 3 day duration?

DonWagner
DonWagner

Is this workaround required in Primavera P.M.?

Vicki.Beckman
Vicki.Beckman

Thanks! The units concept of MS Project has often befuddled me. the Duration X Units = Work formula is just what I needed.

boboxley
boboxley

K(eep) I(t) S(imple) This is the sort of example I've been waiting years for. Microsoft's are just too complicated to follow!

amakar
amakar

Hi - The logic applies to tasks regardless of the length of the duration. The challenge is recognizing a PM should only provide 2 values for the equation and let MS Project calculate the remaining value. Andy

amakar
amakar

Hi Don - I'm not a Primavera user so I don't know how that package calculates units, work, or duration. I'm primarily a MS Project User

lars.aarby
lars.aarby

Why not remove the Effort driven checkmark? If you go to the Task estimation window and select the Advanced folder, next to the task type you can turn the Effort driven calculation on/off. I often use this option to keep Project from taken over the control. From the MS help: "Effort driven Specifies that Project keep the total task work at its current value. The duration of a task shortens or lengthens as resources are added or removed from a task that is effort driven while the amount of effort necessary to complete a task remains unchanged. By default, this check box is selected when Fixed Duration or Fixed Units is the selected task type."

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