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How does Project calculate Actual Duration when manually updating Actual Work in the timesheet ?
Question

Hello,
Please explain of how Project calculates Actual Duration when I manually entered the Actual Work in the timesheet portion of the Task Usage View.
Lets say we have a fixed unit 3day task with a single resource assigned to it at 100% capacity.
So we will have he following:
Now I will enter the Actual Work of 4 hours in the timesheet portion of the Task Usage view:
I understand the Project calculated the Remaining Duration of 2.5d as remaining work of 20h divided by resource assignment units of 100% or 8h per day.
But I don't understand of why and how exactly (using scheduling formula) does Project calculate the Actual Duration of 1 day when Actual Duration = Actual Work / Units = 4h/100% = 1/2d. Apparently Project thinks differently.
Can anyone clarify this to me?
Thank you,
Alex
 Edited by Alex Shafir Monday, June 27, 2016 6:04 PM
 Changed type Gary Chefetz, MCITP, MCT, MVP Tuesday, August 16, 2016 12:41 PM
Monday, June 27, 2016 6:03 PM
All replies

Hi Alex,
Actual Duration = Duration x % Complete.
Check out the site below for an indepth description.
https://support.office.com/enus/article/ActualDurationtaskfieldd781ba9330d34a28aecc9fa330fa7984
Thanks,
Jim
Jim Project
Monday, June 27, 2016 7:33 PM 
Below is also a description of Actual Work:
https://support.office.com/enus/article/ActualWorkfields24a925581d3f4013975e7b2842fa0d2b
Jim Project
Monday, June 27, 2016 7:42 PM 
Hi Jim,
In order to use that formula and to calculate the Actual Duration you need to know 2 of the 3 of it's components, that is, the Duration and the %Complete. None of them are known tough.
When I entered the Actual Work , Project recalculated the Duration as Duration = Actual Duration + Remaining Duration. While Remaining Duration could be calculated as Remaining Work / Units, the calculation of the Actual Work leads us back to my question, of how Project calculated Actual Duration to be one working day when the work I entered for that day was only 4 hours.
Thank you,
Alex
 Edited by Alex Shafir Monday, June 27, 2016 10:53 PM
Monday, June 27, 2016 9:39 PM 
Hi Alex,
Just for clarification, here are a few quick definitions:
Duration – Amount of time you think a task will take to complete.
Work – Number of dedicated manhours required to complete a task.
Duration and Work often differ. An example is when you have a resource only available at 50%. In this case Duration would take exactly twice as long as the work itself. Conversely, if you assign two resources at 100% then the Duration will be ½ the work.
Actual Duration  Time that has already elapsed in pursuit of the task.
Remaining Duration – Amount of time remaining (8 hour days) until the task should be complete.
Duration = Actual Duration + Remaining Duration
Actual Work – Number of resource hours already spent working on a task.
Remaining Work – Number of resource hours still needed to complete a task.
Work = Actual Work + Remaining Work
Your duration most likely reflects 3.5 days because Jack only worked 4 hours on the task on Tuesday. Duration is Tuesday, Wednesday, Thursday, and the first half of Friday. This is 3.5 days. Had Jack worked 8 hours on Tuesday, Wednesday, and Thursday then duration would be 3 days.
To verify this select the “Resource Graph” and take a look at Jack. I’ll bet it shows him 50% allocated on Tuesday.
Let me know if this helps.
s/f
Jim
Jim Project
Monday, June 27, 2016 10:59 PM 
Hi Jim,
I couldn't agree with you more on what you wrote.
But MS Project operates not in the descriptive mode but in specific number crunching algorithms like using one or another form of the scheduling formula Work=Duration * Units.
So back to my example, I wanted to use that formula to calculate the Actual Duration. And I could't see of how Project used the formula to calculate the Actual Duration of 1day !
If the Actual Work = 4h and Units = 100% so the Actual Duration for the task with a single resource should have been calculated as Actual Work/Units = 4h/100% = 4h/8h= 0.5 day . But Project calculated I t as 1day instead. How did it do this ?
At the same time the scheduling formula works perfectly in calculation of the Remaining Duration:
1.Remaining Work = Planned Work  Actual Work = 24h  4h = 20h.
2. Remaining Duration = Remaining Work / Units = 20h/100% = 20h/8h= 2.5d.
Thanks,
Alex
Tuesday, June 28, 2016 8:53 PM 
Hi Alex,
On Tuesday Jack was only allocated at 50% because he only spent 4 hours of his available 8 on this task. This means that Tuesday's work is 4h but it's duration is 1d. Take a look at the two scenarios below. One has a duration of 3d and the other has a duration of 3.5d. Both have 24h of work.
Scenario 1 Work % Allocated Duration Tuesday 8h 100 1d Wednesday 8h 100 1d Thursday 8h 100 1d Total 24h 3d Scenario 2 Work % Allocated Duration Tuesday 4h 50 1d Wednesday 8h 100 1d Thursday 8h 100 1d Friday 4h 100 .5d Total 24h 3.5d
Jim Project
 Edited by Jim Project Tuesday, June 28, 2016 10:18 PM
Tuesday, June 28, 2016 10:16 PM 
Jim,
Create a simple fixed unit task. Enter Work = 4 h. Assign a resource at 100%. Project calculates the Duration = Work / Units = 4h/100% = 0.5 day
Although in this example a resource is also being allocated to the task at 50%, MSP doesn't consider the duration to be a 1d task.
I want to get this 1day actual duration number as a result of specific calculations using scheduling formula.
Thanks,
Alex
Tuesday, June 28, 2016 11:23 PM 
This is true because the duration of work that is less than 8h (4h in this case) is on the day the task is completed. This allows it to be .5 day duration. Notice the difference below:
If you create a task with 12 hours of work and do 4 hours on day 1 then 8 hours on day 2 your duration will be 2 days.
If you create a task with 12 hours of work and do 8 hours on day 1 then 4 hours on day 2 your duration will be 1.5 days.
Jim Project
Tuesday, July 5, 2016 3:52 PM 
Hi Alex,
I agree with Jim. I have also created the schedule as per your Question, tried to explain how Actual Duration Works:
For Example, Planned work for ‘Alex Shafir’ 24h
Task Usage View BEFORE Actuals in Schedule
Alex did 'Actual Work' in previous week 12h only so rest of the work (12h) moved automatically to this Week (Refer TimePhased View in below screenshot) and Alex has consumed 5 days to complete 12h work in previous week. Hence, Duration changed to 6.5days and Actual Duration set to 5 Days. Refer the the formula for Actual Duration:
Hope this answer your query.
Cheers, Badal Ratra MCTS
Monday, July 11, 2016 9:35 AM 
Jim, Badal,
Thank you guys,
Alex
Thursday, August 11, 2016 11:22 PM