Question on duration calculation

[Cornhusker]

I’m trying to find a summary of how Project derives the final result for the
duration field? Which inputs does Project consider, and in what order, before
calculating the equation: Duration = Work / Assignment Units?

Any help would be much appreciated. I've look through countless help pages
and internet articles without success.

 

[Jack Dahlgren]

Depends on the task type.
Fixed duration means it takes duration as an input.
Fixed work means you change units and duration changes
Fixed units means changing work will cause duration to change.
There are other subtleties like effort driven tasks etc. which can change
the equation and behavior.

-Jack Dahlgren

 

[Cornhusker]

Jack,

Thanks for the speedy reply but I'm trying to find the entire process that
Microsoft Project goes through to calculate the duration field, including all
the needed inputs prior to calculating the “duration†equation. I should note
that I am using Microsoft Project 2000.

For instance, I know you can gain some control over how this equation
affects your Project by changing the task type functions you described. Also,
I know you can change what Project defines as a "day" through your Calendar
Options under your Tools menu.

So, I’m guessing Project looks for all the inputs (I'm assuming there are
more than the two above) and then will calculate the equation: Duration =
Work / Assignment Units. Do you happen to know the basic “programming rulesâ€
that Project uses to derive at the final result for the duration? Or every
input Project will consider, and in what order, before calculating the
“duration†equation?

Thanks in advance.

 

[Jack Dahlgren]

It is not so complicated.
If I put in a task with 40 hours of work and a resource with units of 100%,
then the duration will be 40 hours.

How project does this internally is of little concern since you can't see it
and can't change it.

The order changes depending on the task setting.

There are only a maximum of 36 possibilities (3 task types x 2 effort driven
options x 6 possible orders of entry), so it is something that you can check
on your own in a using Project. Make a table, then make the changes and
observe the results.

Now, remember, duration of a summary task is NOT calculated using work or
units. It is simply the difference (in working days) between the start of
the earliest sub-task and the finish of the latest sub-task.

Is there a specific reason you are asking about this? Is there a problem you
are having or it is just curiousity?

-Jack

 

[Jim Aksel]

Apologies for the jump in. Perhaps you can tell us what end result you seek
so we can better help you.

If you are having a specific problem, please describe the problem and why
you feel it is inconsistent with your expectation.

Duration = Function of (Actual Work, OT Work, Remaining Work, Max Assignment
Units, Actual Assignment Units, Hours/day-week-month, Resource Calendar
availability, ...). Time for project is calculated in minutes...