PRJ: How Percent Complete Is Calculated for Nested Summary Tasks

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In order for Microsoft Project to speed up calculations, the percent complete of a summary task is based on its direct subordinate tasks and subordinate summary tasks percent complete (if any).

Project uses the following calculation:

   Percent Complete = Actual Duration / Duration
				

For a summary task, percent complete is first calculated from its immediate subordinates, and then actual duration is determined. For a task, either percent complete or actual duration can be solved.

The following example assumes a default base calendar with no resource assignments:

   Name             Outline   Dur   Sch St   Sch Fin  %Comp   Act Dur

Top Summary           1       8d    1/1/96    1/10/96   23%    1.8d
Subordinate Summary   1.1     5d    1/1/96    1/5/96    25%    1.25d
   task1              1.1.1   1d    1/1/96    1/1/96    50%    0.5d
   task2              1.1.2   1d    1/5/96    1/5/96     0%      0d
 task3                1.2     1d    1/10/96   1/10/96   10%    0.1d
				

NOTE: In Microsoft Project 98/2000, the Percent Complete is 20% instead of 23% and Actual Duration is 1.6d instead of 1.8d.

Percent Complete of the "Subordinate Summary" is calculated like this:

   (1d*50%+1d*0%)/2d=25% [(task1 dur) * (task1 %Comp) + (task2 dur) *
   (task2 %Comp)] / [(task1 dur) + (task2 dur)]
				

Percent Complete of the "Top Summary" is calculated like this:

   (5d*25%+1d*10%)/6d=22.5% (=23%) [(Subordinate Summary dur) *
   (Subordinate Summary %Comp) + (task3 dur) * (task3 %Comp)] / 
   [(Subordinate Summary dur) + (task3 dur)]
				

Because the duration of the "Subordinate Summary" does not equal the duration of its subordinate tasks, the percent complete of the "Top Summary" task does not reflect the percent complete values of the tasks themselves.

If the Percent Complete of the "Top Summary" was based on only the subordinate tasks, and not the "Subordinate Summary," it would be calculated as follows:

   (1d*50%+1d*0%+1d*10%)/3d=20% [(task1 dur) * (task1 %Comp) + (task2
   dur) * (task2 %Comp) + (task3 dur) * (task3 %Comp)] / [(task1 dur)
   + (task2 dur) + (task3 dur)]