Home > Agile, Leadership, Microsoft Project, planning > Microsoft Project Tutorial Part 17 – Messing up Work, Duration and Unit

Microsoft Project Tutorial Part 17 – Messing up Work, Duration and Unit

As I explained in a previous post; Work, Duration and Unit are key elements of Microsoft Project. On the surface, it all makes sense. But sensible is not always realistic.

Let us work from this example. Just to simplify, we keep the default settings with a 40 hours week. I know that is not realistic, but that is an issue in itself, and this was covered during lesson 16.

We create the following tasks:


We also create resources Bob and Alice. I’ve also included the field Work so you get the complete picture.

What we first do is that we add Alice as a resource on task A:


Then we add Bob as a resource on the same task:


What happened? Well, the work was split between Bob and Alice, so it took half the time to perform the task. Now look at what happens when I select task B and assign Bob and Alice at the same time:


What happened this time is that there was no division of work. So, if you use the default settings in Microsoft Project, this will be the case. Guess if many fall in this hole. And either abandon Project or just continue doing it wrong.

The answer is knowing your way around task type and Effort driven. Task type affect what happens if you change one assignment (Alice being assigned to Task A) while Effort driven controls what happens when resources are added to a task (Bob is added to Alice as assignee on Task A). You can change these values in the Task Information dialog box.


Task type specifies which value is fixed during the next calculation when you change Work, Duration or Unit.

When I brought this up during a previous post, I mentioned that you should stick to one or two of these types, but that is theory. You need to understand at least Fixed Duration (with Effort driven unselected) and Fixed Work (where effort driven is always selected).

The main problem with Fixed Duration is that a task can never become longer or shorter if you add or remove resources. All that can happen is that people work harder or less during that period. In theory this is applicable to a meeting. A meeting does not become shorter if a participant is removed. But still, isn’t that kind of true? If you’re having a meeting for 3 people or 100 people changes a lot and the latter meeting will probably take longer. For example if all are to say something this meeting will take longer.

The main problem with Fixed Work is that the resources are seen as interchangeable units. If you add another resource, things take shorter to accomplish. Well, if you believe in cloning this can be true, but this is not the case in real life. And this scenario can be a killer during the project. Let’s say that you’re running late in the last sprint of a long project. You are given the question that if you add a resource or two; won’t things take shorter time?

If you ask Microsoft Project, the answer will be yes. The simple formula says that the more resources, the shorter will it take. It does not take into consideration that new resources have to be trained, newbies make mistakes because they don’t know the code, etc.

So, what am I saying? I say that Microsoft Project is not a project manager or a resource planner. It’s a tool which you need to understand in detail if you’re going to use it to do your project management or your resource planning. The problem is that the simplicity of the formula can trick you into thinking that project management is easy and simple. You might not see your own errors.

Is Microsoft Project the best tool? I couldn’t say. Microsoft Excel is no better and I guess other applications for project management struggle with the same problems.

What you can do is stop hiding behind these formulas, bring some common sense into your project management and if you need to; use some tool to help you visualize your Project.

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