Hi,

very often I have questions like this one:

*Dear Nenad,*

*I am going to develop a scheduled for a petrochemical plant shutdown project. My question is: “What percent complete should i use (% Complete or Work % Complete) and why?”*

I wrote a blog Post about this issue, but I will now clarify exactly where is the difference between this two % of completeness, and when to use which one of them.

I will create a very simple Project with one single Task in **MS PROJECT 2016:**

I am going to create two Resources, John and Mary:

Now. Let’s say that Mary has day off at Wednesday, 05.10.2016:

I will assign them to the Task:

As you can see Duration is now 6 days. Now I will switch to the *Task Usage View*, an I will add some columns in it:

As you can see, Duration is 6 days. Why? Initial Duration was 5 days, (from Monday to Friday), but since Mary has day off at Wednesday, she should work on next Monday to finish her part of the Task, and it makes 6 days.

John will work 100% which means 8 hours per day and that make Total of 5 (not 6, but 5!!!) days * 8 hours per day * 100% = 40 hours. Mary will also work 100% and that also make Total of 5 days * 8 hours per day * 100% = 40 hours. . So to finish this Task 80 hours of work is needed.

Now, let’s say that we put 50% in %Complete field. We will get:

50% in %complete field means that we **spent 50% of Duration!** So the work was done according to plan at Monday, Tuesday and Wednesday! You can see that in right part of *Task Usage View* in *Actual Work* field per day.

So John spent 24 hours (8 hours at Monday, Tuesday and Wednesday), but Mary spent only 16 hours (8 hours at Monday and Tuesday, and she did not work at Wednesday, because she had day off!).

Now let’s calculate %Work complete for this example.

- John has to work 40 hours, and he spent 24 hours, so that means 24/40=0,6 or 60%
- Mary has to work 40 hours, and she spent 16 hours, so that means 16/40=0,4 or 40%
- From the Task point of view, John and Mary have to work 80 hours and they spent 40 hours, so that means 40/80=0,5 or 50%

Now let’s say that we did not put 50% in %Complete field, for the Task but instead of thet we put 50% in %Work Completed field. We will get the same result, so I will not show you the same picture again. But I will show you how MS PROJECT calculate %Complete in this example:

- From the Task point of view, John and Mary have to work 80 hours and they spent 50%, so that means 80 * 50% = 40 hours spent on the Task
- John and Mary worked on Monday, which is 16 hours together, and Tuesday which is another 16 hours (so for now, Total is 32 hours), and John worked 8 hours at Wednesday (and Mary was at her day off), so Total is 40 hours spent of the Task
- John has to work 40 hours, and he spent 24 hours, so that means 24/40=0,6 or 60%
- Mary has to work 40 hours, and she spent 16 hours, so that means 16/40=0,4 or 40%

BUT! Suppose that John spent 50% of his Work on the Task, and Mary only 20%. It means that John has worked 40 hours*50% = 20 hours, and Mary has worked 40 hours * 20% = 8 hours. If I put this values on %Work Completed I will get:

From the Task point of view, John and Mary have to work 80 hours and they spent 28 hours, so that means 28 / 80 = 0,35 or 35% of %Work Completed

To calculate %Complete I need *Actual Duration* which is 1,57 days. It is calculated in this way:

- For both John and Mary, if they work full time they have to work 16 hours at Monday. And they did. So this make
**1 day**
- For both John and Mary, if they work full time they have to work 16 hours at Tuesday. And John worked 8 hours, and Mary didn’t work at all . So this make
**0,5 days **(8/16=0,5)
- For both John and Mary, if they work full time they have to work 16 hours at Wednesday. And John worked 4 hours, and Mary didn’t work at all . So this make
**0,25 days **(4/16=0,25)
- So, in total it is 1 + 0,5 + 0,25 = 1,75 days. And this means that %Completed is
*Actual Duration / Duration = 1,75 / 6 = 0,29 or 29%*

Now, final conclusion.

- When you know how much time has passed (e.g Duration) in percentage, use
**%Complete field.**
- When you know how much work is done (e.g Hours) in percentage, use
**%Work Complete field.**
- When you know how much work is done (e.g Hours) in percentage for specific resource, of course you will use
**%Work Complete field. And this is the most common situation if we are talking of percentage.**
- But, if you know exact number of hours that particular Resource spent on the particular Task, never use %Work Complete, but always Actual work field!

Regards!