Successful Project Management: Modifying the Project Schedule

  • 3/15/2011

Adjusting Resource Allocation

Changing the percentage that you allocate resources to tasks may change the schedule duration and cost, depending on whether you reduce the percentage to remove resource overallocations or increase the percentage to shorten duration. In Project, you can take two approaches to modifying the allocation of people to tasks, and the following sections explain how to do both:

  • Changing the units that resources are assigned to a task. This approach changes the number of hours that resources work on that task each day. If you increase the units, the task takes fewer days to complete. Increasing units is easy in Project, but in the real world, it only works for so long. People get tired of working long hours and they begin to make mistakes. And if they don’t earn overtime pay, morale decreases even faster still.

  • Contouring resource assignments. Contours adjust how much people work on their assignments at different times during the task duration, such as starting off slow, working full time in the middle, and tapering off near the end. These contours are often a more realistic model of the time that people spend on tasks than all or nothing.

Changing Units

Modifying resource assignments can be a game of hide-and-seek with Project if you don’t understand how the program calculates resource assignment fields. If you create a task with the Task Type set to Fixed Units, you can type a task name and duration, choose a resource, and click OK. Project sets the units to the resource’s maximum units (for example, 100 percent for full time) and calculates the work. If you want to change units (or make other modifications), assignments may seem less cooperative. This section explains how Project calculates the fields for resource assignments, so you can change units or other values and get the results you want.

Resource calculations depend on the relationships among task duration, work, and units. You can calculate any one of the values as long as the other two fields are set:

Duration = Work / Units

Work = Duration × Units

Units = Work / Duration

Most of the time, deciding what to do is easy. If you specify duration and units, Project uses them to calculate work. If you specify work and units, Project uses them to calculate duration. You can even leave units blank and specify a value for work; Project simply sets the units to 100 percent and then calculates the duration.

Sometimes, you want to change values for a task assignment in a way that conflicts with Project’s bias. In these situations, the Task Type field tells Project which field to keep fixed when you assign resources. For example, a Task Type of Fixed Duration tells Project to change work or peak units. For fixed-work tasks, Project keeps the value for work the same and instead recalculates duration or peak units. Table 13-1 shows the relationship between task types and field calculations.

Table 13-1 Project Recalculates Different Fields Depending on the Task Type

Task Type

Change Duration

Change Assignment Units

Change Work

Fixed Units




Fixed Work

Peak Units



Fixed Duration



Peak Units

Armed with this newfound knowledge, you can now change assignment units on a task with ease. Here are the steps:

  1. If necessary, display the Task Form in the bottom pane of the Gantt Chart view. (If the Gantt Chart view shows only one pane, on the View tab, in the Split View group, select the Details check box. In the drop-down list, choose Task Form.)

  2. In the top pane of the Gantt Chart view, select the task you want to modify.

  3. In the Task Form, in the Task Type list, choose the task type for the field you want to keep. For example, if you want the number of work hours to stay the same and the duration to change, choose Fixed Work.

  4. In the section of the Task Form that shows resource assignments, select the person’s Units cell, and change the value to the new percentage that the person is available. For example, if someone was assigned at 50 percent, type 100% to change it to full time.

  5. Click OK. For a fixed-work task, Project recalculates the task duration.

  6. To keep your tasks consistent, change the Task Type back to Fixed Units.

In the top window in Figure 13-3, the crew member works half-time (50 percent) for 8 days to complete 32 hours of work. In the bottom window, by setting the Task Type to Fixed Work and changing the units to 100 percent, the crew member performs 32 hours of work in only 4 days.

Figure 13-3

Figure 13-3 Change the Task Type to tell Project which field you want to keep the same value.

Adjusting Work Contours

The Work Contour feature in Project changes the allocation of resources over the course of their assignments. For example, you can apply the Bell work contour, which starts someone’s assignment slowly, increases to a higher allocation in the middle and then tapers off the assignment at the end, as demonstrated in Figure 13-4. Contouring tasks can help you optimize your schedule by modeling assigned time more realistically. For example, the work that people have to do on a task often dwindles at the end, so you might be able to start a new assignment before the previous one is complete without overallocating anyone.

Figure 13-4

Figure 13-4 Work contours adjust the allocation of work for resources over the duration of their assignment.

Here are the steps for applying a work contour to a resource assignment:

  1. On the View tab, in the Task Views group, choose Task Usage. (Or in the Resource Views group, choose Resource Usage.) These are the only two views that show detailed assignment information.

  2. For the task whose assignment you want to contour, double-click the name of the resource, Crew Member in Figure 13-4.

  3. In the Assignment Information dialog box, in the Work Contour list, choose the contour that you want. For example, Back Loaded adds more time at the end of the assignment, which is similar to a crunch at the end. Front Loaded adds more time up front.

  4. Click OK to contour the hours.