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Excel/Adding hours to Start date to get workday


QUESTION: Hello, I am trying to calculate an end date with the following criteria:

A1 - start date
B1 - Vacation, sick days
C1 - US Public Holidays
D1 - # hours duration of the task
E1 - Resource Efficiency rating %
F1 - # of resources

I am trying to find a calculation for the end date, for example:

A1 - start date = 9/15/2014
B1 - Vacation, sick days = 14 days [need to deduct these days to get the available time available]
C1 - US Public Holidays (List)
D1 - # hours duration of the task = 3,268.64
E1 - Resource Efficiency rating 95% - [the rate at which you could complete the task.]
F1 - # of resources = 1.6

It needs to calculate the workday [exclude holidays and weekends]

Thanks so much for your help!

ANSWER: The WORKDAYS feature will most the one you will utilize.  

  =WORKDAY(start_date, days, [holidays])

Start_date = A1

  =WORKDAY(A1, days, [holidays])

Days... here's your puzzle.

Let's assume 8 hours per day.  You say efficiency is 95% and I'm not sure what that means exactly.  In hours 5% of the time is non-productive?  So in an 8 hour day we only complete 7.6 hours of work?  So a 7.6 hour workday.

We divide the # hours duration of task by our workdayhours to get the number of days needed.

We slip that into the formula for "days":
  =WORKDAY(A1, D1/(8*E1), [holidays])

For HOLIDAYS, you will enter the range of cells that hold the dates to be included.  The list must be comprehensive, so be sure to expand your list to include the holidays going forward as many years as needed.  Each cell in the range holds a single date.

So, let's assume you have a sheet called Holidays and you are listing those holidays in column A.  We add that to the formula:

  =WORKDAY(A1, D1/(8*E1), Holidays!$A:$A)

Anyway, that should give the idea.  The answer given back by this formula will be a date in the future.

I'm not certain I understand the ramifications of F1, # of resources.  Perhaps you would divide the "days" by that number?

     =WORKDAY(A1, D1/(8*E1)/F1, Holidays!$A:$A)

---------- FOLLOW-UP ----------

QUESTION: Thank you very much! The number of people on the team is in F1 to do the work, so the date would also be affected by how many people are on the team; the more people on the team, the faster we will get the job done.

Also, how about B1 (vacation/ sick)?

What about B1?   Since there are only 3 parameters in the WORKDAYS function,

       =WORKDAY(start_date, days, [holidays])

... you just need to decide where you want it to slip in.   Pure guess on my part would be on the "days" calculation. Currently the days calculation is:


Do you want to add vacation days to this?


So the final result might be:

    =WORKDAY(A1, (D1/(8*E1)/F1)+B1, Holidays!$A:$A)
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Jerry Beaucaire


Excel Formulas, macros, automation. Microsoft Excel MVP - 2010. Code site with free code snippets and techniques:


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Bachelor's Degree from Azusa Pacific University in Mathematics and Music Composition

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