Scheduling formula question

[TBol]

I know both are the same equation. Which one is by definition ? "Duration =
Work / Units" or "Work = Duration x Units".
I have a three day task with a resource assigned (Max. Units 100%,
Units:100%). All calendars are the default Standard base calendar; Hours per
day is 9 hours. How do we build the equation to calculate 27 hours of work ?

 

[Dale Howard [MVP]]

TBol --

To be technically correct, the Duration Equation formula is written as:

Duration = Work/(Hours Per Day x Units)

You find the Hours Per Day value on the Calendar page of the Options dialog,
accessed by clicking Tools - Options - Calendar. You were missing one key
part of the formula, which is the Hours Per Day value. Hope this helps.

 

[Andrew Lavinsky]

Most people use D = U X W, which means W = D/U

It's really D = (U X PHPD) X W, where PHPD = Person Hours Per Day.

Then just pick which variable to solve for.


- Andrew Lavinsky
Blog: http://blogs.catapultsystems.com/epm

 

[Andrew Lavinsky]

My bad. Please belay that last note, let's try it again:

D X U = W, should really be D X (U X PHPD) = W, with PHPD = Person Hours
Per Day.

Then solve for the correct variable.


- Andrew Lavinsky
Blog: http://blogs.catapultsystems.com/epm

 

[TBol]

Thanks Dale. Sorry, I did not explain well. I've changed "Hours per day"
setting into 9 hours on Calendar tab of the Options DB. My task duration is 3
x 9 = 27 hours and
I need 27 person-hours to complete the task. On the other hand, resource has
8 hours per day. Project will spread the resource hours as 8,8,8,3. I am
fine with all that.

The formula is (single task - single resource) as follows:
Work = Task Duration x (Resource Hours Per Day x Units).

What I don't understand is that if we build the work formula based on the
working hours of resource (which is 8 hours per day) how can we get 27
person-hours out of "Work = Duration * Units" calculation.

 

[Dale Howard [MVP]]

TBOL --

In Microsoft Project, the system calculates Duration, Work, or Units for
EVERY task using the exact same formula. This means that the formula does
not take into account the resource's work schedule as defined on the
resource's calendar. So, this means if you have specified the Hours Per Day
value as 9 hours, then the formula will compute Work using that number for
every task, even though your resources only work 8 hours per day. Now, my
question for you is why do you have a different Hours Per Day value from the
number of hours on each resource's calendar? It sounds to me like your
calendars are out of synch. Hope this helps.

 

[TBol]

Thank you Dale. I am just trying to understand how it works. I'll keep both
synched.
Thanks a lot.

 

[TBol]

Thank you Andrew.

My bad. Please belay that last note, let's try it again:

D X U = W, should really be D X (U X PHPD) = W, with PHPD = Person Hours
Per Day.

Then solve for the correct variable.


- Andrew Lavinsky
Blog: http://blogs.catapultsystems.com/epm



.

 

[Steve House]

Note that chqanging the "hours per day" field on the Tools/Options menu,
Calendar page DOES NOT affect the calculations where the hours worked per
day enter in. This field is actually a conversion factor, used by Project
to convert a duration entered in the units of "Days" or "Weeks" into units
of hours, hence minutes, for storage in the task database. To change the
hours per day that the resource works such as is used in the equation Dale
cites, you must modify the calendar workday using the Tools,
ChangeWorkingTime menu option. The Calendar Options page does not affecgt
that.

 

[TBol]

Thanks Steve.

Note that chqanging the "hours per day" field on the Tools/Options menu,
Calendar page DOES NOT affect the calculations where the hours worked per
day enter in. This field is actually a conversion factor, used by Project
to convert a duration entered in the units of "Days" or "Weeks" into units
of hours, hence minutes, for storage in the task database. To change the
hours per day that the resource works such as is used in the equation Dale
cites, you must modify the calendar workday using the Tools,
ChangeWorkingTime menu option. The Calendar Options page does not affecgt
that.
--
Steve House
MS Project Trainer & Consultant




.

 

[Dale Howard [MVP]]

Steve --

Thanks for your excellent clarification!