Hi,

here is one problem that my Blog Reader has (I will go step by step, and I will use MS PROJECT 2016)

“When multiple resources are assigned to the task, for a given Total Work we can  calculates the   Duration either as Work divided by  Total Assignment Units   OR  by calculating the Duration for each individual resource  as Duration (Ri) = Work (Ri) / Units (Ri))  and then selecting the longest duration of the driver resource to be a task Duration. For example, let’s say we have a 3d, 36 hr task for 2 resources R1(100%)  and R2(50%)”

As you can see task is Fixed work type, and I put 3 days in the Duration.

Now I am going to create two Resources, one with 100% units, and other with 50%:

and I’m going to assign both Resource to Task:

What is wrong with this Scenario. Technically nothing, but logically, if you have Fixed Work Task, it means that work is fixed, and that you know how much work you need for the Task. An, in this scenario, you should not put Duration, but Work. But, let’’ me continue with scenario from my Blog reader, and I’m going to show you Task Usage View:

As you can see R1 should work 3 days and 8 hours per day which is 100%, and it equals 24 hours. On the other hand, R2 should work 3 days and 4 hours per day which is 50%, and it equals 12 hours.

My Blog reader continues with: “Now I enter Actual Work of 10h into resource R1  and we get:”

The question from my Blog reader is:

“So we can’t anymore use the same approach to calculate Actual Duration using the Actual Work and Units of individual assigned resources. That is, if we calculate the Actual  Duration using the only Actual Work R1 we will get:
Actual Duration = Actual Work (R1) / Units (R1) = 10h / 100% = 1.25d which is not what shown on the screenshot above (0.83d).
So the only way to get Actual Duration right is to calculate it as:
Actual Duration =  Sum of Actual Work of each resource /  Total Units =( 10h + 0h) / (100% + 50%) = 10h/150% = 0.83d

So why is  the method of calculating the task  Duration based on the individual resource Work and Units  with subsequent selection of the longest duration doesn’t work for an Actual Duration calculations?“

Well, Microsoft Project does not calculate Actual Duration in that way. Let’s take a look on the right side of the Task Usage View:

As you can see:

• At Monday Work was 12 hours, and Actual Work is 8 hours (Because R1 works only 8 hours per day). Actual Duration is: Actual work / Work = 8 /12 = 0,66666
• At Tuesday Work was 12 hours, and Actual Work is 2 hours (Because R1 works remaining 2 hours of 10 hours assigned as Actual work). Actual Duration is: Actual work / Work = 2 /12 = 0,16666
• So Actual Duration is 0,6666 + 0,16666 = 0,83 Days!

So that is Actual Duration for the Task. And it is always calculated with work and Actual work of all Resources, not one by one!

Regards!