One of the more confusing aspects of Microsoft Project is Task Type. Task Type can be set to "Fixed Units", "Fixed Work", or "Fixed Duration" for each task.
How to Set Task Type
You can set task type in a couple ways:
1. If you select a task or tasks and go to task information (under project in the menu or right click and its there as well) you will find task type in the advanced tab.
If you select all your tasks, you can set the Task Information for every task to the same Task Type – this will lead to less confusion when you are adjusting your plan because all the task types will be consistently set.
There is also a check box (which is checked by default) that says that tasks are “Effort Driven”. When this is checked, it is assumed that work stays constant even if you adjust the other two measures. So for example, if you change a 40 hour task from 1 week duration to 2 weeks duration, project will keep the 40 hours of work but decrease the number of resources required to compensate (only 50% of a resource in this case).
This may not be what you want and I find particularly with using Fixed Duration having this turned off is highly desirable because want to adjust the work, not the units. For example, what I want is to tell project, “I want to schedule this task with 1 person for 2 weeks” and have it calculate work to be 80 hours. If I adjust the schedule to be 3 weeks, I want the work to increase by 50%. Similarly, if I am working in Fixed Duration and I double the resources, I want the duration to stay constant and for the work to double. This will only happen if “Effort Driven” is turned off.
How Task Type Works
Any task can be adjusted using three measures: Units, Duration or Work. Because each measure is dependent on the other, at least one of the other two must be impacted. By changing the task type, you are telling project which measure you are going to adjust and which measure should be automatically re-calculated. Below is a chart that shows how Project reacts based on the task type:
|Field that you change||Field calculated if the task is Fixed Units||Field calculated if the task is Fixed Work||Field calculated if the task is Fixed Duration|
|Work||Duration is recalculated||Duration is recalculated||Units are recalculated|
|Duration||Work is recalculated||Units are recalculated||Work is recalculated|
|Units||Duration is recalculated||Duration is recalculated|| |
Work is recalculated
Basic Tips for Using Task Type Efficiently
Here are some basic tips to using Task Type efficiently and to avoid confusion:
- Pick the task type that makes sense for you and use it consistently. I tend to think in Duration with Effort Driven turned off first and what I want is to calculate the number of hours (and therefore cost) required to do the work. Other PMs like thinking in work instead and want to adjust the schedule instead. Pick an approach before you start and be consistent with it.
- You can switch the task type without impacting your plan. Therefore, feel free to change the task type for the specific scenarios below.
Scenarios to use Specific Task Types
I used Fixed Duration when I have a good understanding of the schedule and the team and I want to calculate cost/effort. A good example of this is doing a plan for requirements gathering interviews. I know that I have 2 weeks of interviews, 1 week of documentation and 2 days of client review and I know that I need a Business Analyst and a Technical Architect in each one at 100%. Fixed Duration works really well because I can adjust the schedule really easily and the work effort is calculated for me.
Another good use for Fixed Duration is % allocations for overhead resources. Project Managers for example tend to be used on an overhead basis for the duration of the project on a fairly constant basis. If the project takes longer you will need more project management. It’s also easier to think of assigning a PM at 30% to a project for the entire duration than to say, “I need 85 hours of project management for this project). With Fixed Duration, you can simply assign the PM for the entire duration and adjust the % allocation and the work effort is automatically calculated.
A good use of Fixed Work is when you want to try and fit a fixed amount of hours into a fixed schedule. By fixing the work, you can adjust the number of resources you need to impact the duration. For example, let’s assume you have 1280 hours of work and you want to try and jam that work into a fixed 8 week period. With Fixed Work turned on, you can set the allocation of resources to 400% in order fit the fixed amount of work into a duration you wish.
I generally find that using Fixed Units is my least desirable option simply because in most real world scenarios adjusting the number of resources required is the most flexible option.
One scenario where Fixed Units might be appropriate is for department planning. In a department, the number of fixed units is constant (the number of full time employees) and as a Director you want to know how much work your team can produce. What tends to happen in these scenarios is the queue of work is constant and the duration flexes – you end up telling the poor person at the end of the priority list that their project won’t get done until next year.
In this case, setting Fixed Units would allow you to lock in the resource pool based on the size of your department and then adjust the work to calculate the resulting schedule. Based on the schedule, you would then be able to tell your stakeholders how many projects can be done in the coming year.
I hope that provides some guidance on how to use this key function in Microsoft Project – I have found even very senior Project Managers do not fundamentally understand how Duration, Effort and Units work together and how to model them in Microsoft Project. If you understand the conceptual framework and the rules that Microsoft Project uses, you will find that there are less errors in your plan, less confusion and less tearing your hair out when you find Project adjusts your numbers in ways you didn’t intend.