Project Management

Microsoft Project tutorial: Duration and task types

If you're new to Microsoft Project, be sure to check out part one of our Microsoft Project tutorial series. Today, we examine task types and how Project calculates Work, Duration, and Units.

What is Project, and what isn’t it?
Microsoft Project is a very misunderstood application. It is reminiscent of other Office applications, with menus and toolbars like Word, and tables and graphs like Excel, but when you get into it, you see it’s very different. In some ways, it seems to do things on its own.

Project is the most narrowly focused of all the Office applications. While the other Microsoft Office programs tend to be broad and general in their application, Microsoft Project is designed exclusively to manage resource usage and project scheduling.

It will not manage your project for you. It will not stop you from giving your resources too much to do. It will not tell you what is going to happen, but it will let you know what might happen if nothing changed. Just like any other software, Project should be used as an informational system and not as a crystal ball.

Project will help you keep track of the progress of your tasks. It will help you figure out how much each of your resources is doing on your project. It will make it easier to communicate the status of your project.

If you’re new to Project or considering this software as a solution, I’ll explain the basics of Microsoft Project over the next few articles. Let’s begin with a look at how Microsoft Project calculates Work, Duration, and Units.

Microsoft Project series
This is the first of four articles running in IT Consultant and IT Manager Republics designed to provide an introduction to this popular project-management solution. The next installment in this series will discuss entering tasks, making work estimates, deciding task types, and creating dependencies between tasks.

Duration = Work/assignment Units
The calculation of Work, Duration, and Units is the single biggest trouble spot for new users of Project. This calculation is the core of what Project does and it cannot be turned off, so you must deal with it.

Duration = Work/assignment Units: This equation is the E=MC² of Project. It means that, given the other settings in Project—like how many hours in a day, etc.—the assignment Duration (in hours) is equal to the assignment Work (in hours) divided by the assignment Units value. Units are the percentage of a resource’s workday, or the amount of the day the project team member is expected to work on a given assignment. For example, if you want Joe to work half-time on a task, you would assign him at 50 percent Units.

If a resource’s workday is eight hours and he or she is assigned to work on a task at 100% Units (for eight hours of work), then the Duration is eight hours (one day by default).

Now let’s say you change the Units to 50%. Then the Duration becomes 16 hours or two days, because if a person is working half of an eight-hour day on this task, then it will take them 16 hours (two days) to complete eight hours of work.

Lots of people will attempt to argue with this formula, but save your breath and time by just accepting it. It is a Microsoft Project truism, and even if you do not agree with it, this formula is what Project uses.

Everything that Project does is based in some way on the calculations that this formula makes.

Task types
The way that Project gives you some control over how this formula affects your Project is through the task type function.

The task type options are:
  • Fixed Units
  • Fixed Work
  • Fixed Duration

As you might guess from the names, they allow you to “fix” one of the three elements of the equation in order to control what will be adjusted to make the two sides equate.

The Advanced tab on the Task Information menu allows you to choose whether you’d like to fix the value of Units, Work, or Duration.


As you’ll recall from junior-high algebra, if you have a three-element equation and you hold one value fixed, then if you change a second value, the third value must change to keep the equation true. For example:

1 day Duration = 8 hours Work /100% Units

If we create this as a Fixed Duration task type and then change the Units to 50%, Project automatically will change the Work value to four hours.

If we set the task to Fixed Work, then the same change in Units would cause Project to adjust the Duration value to two days. And, if we set the task to Fixed Duration and edited Work to 16 hours, Project would adjust the Units value to 200% in order to keep the Duration value fixed yet still balance the equation.

That said, the best way to become familiar with this function is to create a test Project, play with the settings, and see how Project reacts to changing data or adding actual work.
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