durations not adding up

[Nancy Carpenter]

Sometimes my durations do not add up to the higher level
tasks durations. Why?

 

[Dale Howard]

Nancy --

The Duration value you see on summary tasks is a "summary" of the Duration
across all of its subtasks. It is not a "total" and the numbers may or may
not "add up" on the summary task. For example, the summary task Phase I has
three subtasks beneath it: Task A (5 days), Task B (10 days), and Task C (3
days). Consider these three situations, and notice that the Duration of the
summary task Phase I is different in each case:

1. Tasks A, B, and C are linked with Finish to Start (FS) dependencies.
The Duration of Phase I will be the total of the Durations of the three
tasks, which would be 18 days.

2. Tasks A and B are linked with a Finish to Start (FS) dependency, but
task C is unlinked. The Duration of Phase I will be the total of the
Durations for Tasks A and B only, which would be 15 days.

3. There are NO dependencies between Tasks A, B, and C and all of them are
unlinked. The Duration of Phase I would be the Duration of the longest
task, which in this case would be 10 days for Task B.

To determine the Duration of a summary task, Microsoft Project calculates
from the start date of the earliest-starting task to the finish date of the
latest-finishing task, then subtracts any non-working time periods such as
weekends or holidays. It does not simply total the Duration values of each
subtask. Hope this helps.

 

[Nancy Carpenter]

Thanks!

-----Original Message-----
Nancy --

The Duration value you see on summary tasks is a "summary" of the Duration
across all of its subtasks. It is not a "total" and the numbers may or may
not "add up" on the summary task. For example, the summary task Phase I has
three subtasks beneath it: Task A (5 days), Task B (10 days), and Task C (3
days). Consider these three situations, and notice that the Duration of the
summary task Phase I is different in each case:

1. Tasks A, B, and C are linked with Finish to Start (FS) dependencies.
The Duration of Phase I will be the total of the Durations of the three
tasks, which would be 18 days.

2. Tasks A and B are linked with a Finish to Start (FS) dependency, but
task C is unlinked. The Duration of Phase I will be the total of the
Durations for Tasks A and B only, which would be 15 days.

3. There are NO dependencies between Tasks A, B, and C and all of them are
unlinked. The Duration of Phase I would be the Duration of the longest
task, which in this case would be 10 days for Task B.

To determine the Duration of a summary task, Microsoft Project calculates
from the start date of the earliest-starting task to the finish date of the
latest-finishing task, then subtracts any non-working time periods such as
weekends or holidays. It does not simply total the Duration values of each
subtask. Hope this helps.

--
Dale A. Howard
Project Management Trainer/Consultant
Denver, CO





.

 

[Mike Glen]

You're welcome, Nancy

Mike Glen
MS Project MVP