Calculate date task will be completed in excel

Question

I am building a schedule on excel given that I work a 9/80 work schedule (9 hrs monday through Thursday, Every other friday off, and the fridays i do work i only work 8 hours)

I have a list of tasks along with the number of hours it will take to complete them. I want to add the number of days to my start date to figure out the date I will complete the task. I created a list of off fridays and holidays and am using the workday() function to calculate the date of completion. My problem is that I am not sure how to handle the fridays where i work 8 hours instead of 9, for tasks that are worked on a friday. so for example lets say i start Tuesday and have 36 hours to complete a task during a week where i am working on friday. If i use the workday function it will say that I will complete the task friday of that week but in reality i still have 1 remaining hour left to complete the task and so It will really be completed monday of next week. Any help would be appreciated

Answer 1

As I see it, the trick lies in determining the number of days spent on the task. What you want is to first calculate normal days based on 9 hours a day and then add 1/9 th of a day for every 80 hours spent. Also adjust this calculation for particular day of the start date.

Determine the weekday of the startdate: in J11 enter =WEEKDAY(I11,2) . This will give 1 for Monday, 2 for Tuesday and so on.

Insert a helper column before days column as 'offset days': =E13+CHOOSE($J$11,0,9,18,27,36)

Formula for 'days' column: =(E13/9.001) + QUOTIENT(F13,80)/9

and finally for 'date completed' column: =WORKDAY($I$11,G13, HolidayList) where 'HolidayList' is the name of the range where holidays are listed.

I have tested this minimally and found proper result. You should test this extensively for various startdate and different hours. Let me know if you get expected results.