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Allocate Resources Most Efficiently to Give the Shortest Duration Possible

by Dale Howard, Microsoft Project MVP

Background Information

A user posed an interesting question recently in the Microsoft Project Standard and Professional user forum on the Internet. He asked how to assign resources to a task to generate the shortest Duration possible for the task using the following requirements:

  • The task requires 100 hours of total work for all assigned resources.
  • One resource is available to work full-time and should be assigned at a Units value of 100%.
  • Two other resources are available to work only half-time and should each be assigned at a Units value of 50%


The solution to this problem is not very difficult, but it does require a series of specific steps to force Microsoft Project to calculate the shortest Duration possible for the task. Following are the required steps:

  1. Apply the Gantt Chart
  2. Reset the Duration of the task to the default value of 1 day, if necessary.

Right-click anywhere in the Gantt Chart pane, on the right side of the view, and select the Show Split item on the shortcut menu, as shown in Figure 1.

01 Right-click in the Gantt Chart pane

Figure 1: Right-click in the Gantt Chart pane

This action applies a combination or “split” view known as the Task Entry view. The Task Entry view includes the Gantt Chart view in the top pane and the Task Form view in the bottom pane.

  1. Select the task in question in the task list on the left side of the Gantt Chart
  2. In the Task Form pane, make sure the Task Type value is set to Fixed Units. If not, select Fixed Units and then click the OK
  3. In the Task Form pane, make sure the Effort Driven checkbox is selected. If not, select it and then click the OK Figure 2 shows the Task Entry view with the correct settings for the selected the task.
02 Gantt Chart view with correct settings specified

Figure 2: Task Entry view with the task selected

  1. In the Resource Name column of the Task Form pane, select the name of the resource who can work full-time.
  2. For this selected resource, enter 100% in the Units column and 100h in the Work column, and then click the OK Microsoft Project should calculate an initial Duration value of 12.5 days for the task, as shown in Figure 3.
03 First resource assigned

Figure 3: Initial Duration for the task

  1. Below the name of the first resource you selected in the Task Form pane, select the names of the two other resources who will be working half-time.
  2. For each of these two resources, enter 50% in the Units
  3. Click the OK button ONLY AFTER you have selected the two other resources.

This final step should reduce the Duration to 6.25 days, allocate 50 hours of work to the full-time resource, and allocate 25 hours of work to each of the two half-time resources. The result is the shortest Duration possible for the task, based on the work and resource requirements, as shown in Figure 4.

04 All three resources assigned

Figure 4: Shortest Duration possible for the task

You can see from the previous steps that the answer to this question was straightforward, but not exactly simple. The trick was to use the Effort Driven capabilities of Microsoft Project to allocate the 100 hours of planned work in the most efficient manner between the assigned resources, so that the software would calculate the shortest Duration for the task.


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