@RISK: Summary Task Doesn't Sum the Durations of Subtasks

Summary task duration is earliest start to latest finish, not the sum of subtasks, so overlapping work makes it shorter.

Jan 21, 2026
Knowledge

Title

Answer

Applies to:
@RISK 6.x and Up, Professional and Industrial Editions
@RISK for project 4.x

The duration of my summary task doesn’t equal the total of the subtask durations.

What is wrong?

Answer:
Nothing is wrong. A summary task’s duration is the time from the earliest subtask start to the latest subtask finish, not the sum of all subtask durations. If subtasks overlap or run in parallel, the summary task will be shorter than the total of their individual durations.

Related Article:

Finish Date Unexpectedly Skewed

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summary-task-doesnt-sum-the-durations-of-subtasks