PRJ98: How Work, Duration are Calculated w/Assignment Changes

MORE INFORMATION

When you make multiple resource assignment changes on an Effort Driven task within the same edit session, Microsoft Project calculates work using the following formula:

   Work = Total Work * (Resource Units/Total Resource Units)
				

For example, if you have a 2-day (2d) duration task where a resource (R1) is assigned 200%, the 2d duration task calculates to 32 hours (32h) of work. If you add a new resource (R2) to the task, then Microsoft Project calculates work and duration for each resource in the following manner:

Resource R1 Work:

   21.33h = 32h Total Work * (200% R1 Units/300% Total Units)
				

Resource R2 Work:

   10.67 = 32h Total Work * (100% R2 Units/300% Total Units)
				

Task T1 Duration Calculation:

   2.67d = 21.33h (R1 Total Work)/100% (R1 Units based on 8 hour day)

   1.33d = 10.67h (R2 Total Work)/100% (R2 Units based on 8 hour day)
				

The duration of the task changes from 2d to 2.67d due to the length of time necessary for the driving resource to complete it's assigned work. The driving resource for a task is determined to be the highest ratio of Work/Units for all resource assignments on a task. In this example, R1 is the driving resource because 2.67d is higher than 1.33d. Based on an 8-hour day, it will take R1 2.67d to complete 21.33h of work.

Steps to Reproduce Behavior

1. On the File menu, click New. If you receive the Summary Information dialog box, click OK.
2. Enter a new task, T1.
3. On the Window menu, click Split.
4. Press F6.
   
   The lower pane becomes the active pane.
5. On the Format menu, point to Details, and then click Resource Schedule.
6. Click to select the Effort Driven check box, and then click OK.
7. Press F6.
   
   The upper pane becomes the active pane.
8. Select the T1 task.
9. On the Tools menu, point to Resources, and then click Assign Resources.
10. In the Assign Resources dialog box, enter two resources, R1 and R2.
11. Select R1. In the units column type 200%, and then click Assign.
    
    NOTE: The lower pane R1 is assigned 200% for 32h of work.
12. Select the Resource Names field for task T1 and then press F2.
13. Delete the contents of the field and type "R1,R2" (without the quotation marks) and press Enter.
    
    NOTE: The lower pane R1 is assigned 100% for 21.33h of work while R2 is assigned 100% for 10.67h of work.