Hi,

with permission of my MVP friend Gérard Ducouret I will explain how different Resources working time affect Task duration in MS Project 2013!

I will show you on the example. First, I will create (as I always do), the brand new Project:

I will create two Resources, one will work 8 hours per day, and the other 7 hours per day:

I will now change Standard Calendar for Resource – 7 hours:

and then:

As you can see, this Resource will work only 7 hours per day.

No I will assign Those Resources to Tasks:

Both, Task 1, and Task 2 has 10 days Duration, but the whole Project has 11,38 days of Duration. Why? Let’s look at the Task Usage View (I will make two Pictures):

As you can see Task 1 will be finished at Tuesday 31.3.2015 (two day later than Task 1).

Here is the second part of Task Usage View:

Both Task need 40 hours of work to be done! Why? Hit File Tab, then Options, and then:

So to finish each Task with 10 day Duration it will be needed for 80 hours (10 days * 8 hours per day)

Task 2 will be done with Resource who will work 8 hours per day, so it will start at Monday, and it will be Finished next Friday, because 80 hours = 80 / 8 hours per day = 10 days,

Task 1 will be done with Resource who will work 7 hours per day, so it will start at Monday, and it will be Finished at Tuesday after two weeks. Where the 11,38 days is coming from? If you look at the second picture form the Task Usage View, you will see that Resource – 7 hours per day will work 11 full days (7 hours per day), and at last day it will work only 3 hours, eg 3/8 = 0,38 days. So 11+0,38 = 11,38 days.

I know what you do not understand! Why is duration for Task 1 = 10 days! Frankly, I do not know. From my point of view  it should be 11,38

Now let’s look at the Detail View:

This is Fixed Units Task type.

But what if you want that both Task have 10 days duration, no matter who will work on them, and how many hours will someone work on them?

I will now change this to Task to Fixed Duration type:

Now Task has “right” Duration, but that is not what I want! I will change Duration to 10 days:

and I will get:

or / and (Second Picture):

It’s tricky, isn’t it?

Regards!