Change the task type for more accurate scheduling

You just assigned a few people to a task, and the task duration got longer, not shorter as you expected. Or maybe the reverse happened. Either way, you’re stumped. Some tasks, such as curing cement, take a fixed amount of time no matter how workers are assigned to pouring the cement. Others, like building roads or software, grow or shrink in their durations, depending on the people and resources applied to them.

  • To change the task types to better reflect these realities, double-click the task, click Advanced, and change the task type.

Tip:  To speed things up, add the Task Type column to a sheet view. Right-click on a column heading and then click Insert Column.

Look closer into task types

How task types change your schedule

A real-world example of controlling the timing of tasks

How task types change your schedule

Project uses a scheduling formula that relates the three values of work, duration, and assignment units:

Work = Duration x Units

Setting a task’s type allows you to “fix” (or make unchangeable) one of these values. Fixing one of the values places a priority on that value by telling Project not to change it when the other two values change. This applies to both automatically and manually scheduled tasks.

Here’s a handy table to help keep all the moving parts of the scheduling formula in mind.

In a

If you revise units

If you revise duration

If you revise work

Fixed units task

Duration is recalculated.

Work is recalculated.

Duration is recalculated.

Fixed work task   

Duration is recalculated.

Units are recalculated.

Duration is recalculated.

Fixed duration task

Work is recalculated.

Work is recalculated.

Units are recalculated.

Let’s look at the three task types more closely. Fixing one of these values gives you powerful control over your schedule. But before you read on, make sure you understand the difference between the three pillars of Project scheduling: work, duration, and units and how they relate to each other. For a quick refresher read How Project schedules tasks: Behind the scenes.

People stumble over this all the time, so don’t be discouraged if you don’t get it right away. Mastering it will help grow your expertise as a project manager once you understand how to control task durations with task types.

The table below summarizes the task type and the impact on the schedule.

Task type

Impact on schedule

Fixed units

This setting assumes the number of people assigned to the task (units) is known and you don’t want it to change, even if duration changes. When the work changes on a task, the duration changes, but not the number of people. This task types reflects most task realities in any project.

Example: You have one person assigned to write a report that should take only two hours to write. If you decide that the reality of work on this report is that the two hours needs to be spread over two days on the calendar, you can change the duration to two days—without changing the number of people assigned to write the report. After all, you probably don’t want more than two people writing the report anyway. In other words, you want the number of units (the one person) to stay the same.

Note:  This is the setting Project typically places on tasks. To change this default setting, click File > Options > Schedule, then select a different task type in the Default Task Type list.

Fixed work

This setting assumes work doesn’t change, even after changing durations or adding people. Use this setting if you want to control the duration of tasks by adding or removing people.

Example: It takes 300 hours to design a large garden as part of a housing project. And you want the garden built as soon as possible, so you start assigning more gardeners to the job (task). The duration of the garden task will decrease as you add more people.

Note:  You can’t change the Effort driven setting for a fixed-work task. Project doesn’t consider fixed work tasks to have flexible work values and are therefore always effort-driven. You can change the effort driven setting for task types.

Fixed duration

This setting assumes duration doesn’t change, even when more people are assigned to the task. Use this setting if you have a duration in mind for a task before you know other information about the task.

Example   : A weekly status meeting might take an hour. Set this task to fixed-duration, otherwise as you assign people to the task, the duration of the meeting will decrease. And we all know, adding people to meetings isn’t likely to decrease their length (it could even make them longer!)

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A real-world example of controlling the timing of tasks

The following three scenarios demonstrate the ripple effect (and thus control) that task types have over the timing of tasks throughout the schedule.

Scenario one: Changing task type to fixed-units

Let's say you have a fixed-units task, with 1 full-time person available for 8 hours a day. Further, you’ve set the task up with a 10-day duration and 80 hours of work.

What you change

What Project does

Add a full-time resource

Project recalculates the task's duration. The task now has 2 units assigned, with a 5-day duration and 80 hours of work.

Increase the duration

If you have 8 days to complete the task rather than 10, Project recalculates the task's work. The task now has an 8-day duration, with 64 hours of work, and 1 resource unit.

Change the work

If the task will take 20 hours of additional work, Project recalculates the task's duration. The task now has 100 hours of work, with a duration of 12.5 days, and 1 resource unit.

Scenario two: Changing task type to fixed-work

Now you make the same task a fixed-work task. This means that the task can take only the amount of work you specify: no more, no less. Remember, the task has 1 full-time person available for 8 hours a day, and it has a 10-day duration with 80 hours of work.

What you change

What Project does

Add a full-time resource

Project recalculates the task's duration. The task now has 2 units assigned, with a 5-day duration and 80 hours of work.

Increase the duration

If you have 8 days to complete the task rather than 10, Project recalculates the task's resource units. In order to get the task done in 80 hours over 8 days, 1.25 resource units must be assigned. The resource unit that is currently assigned to the task is over allocated at 125%. You need to assign another person to account for the additional 25% allocation.

Change the work

If the task will take 20 hours of additional work, Project recalculates the task's duration. The task now has 100 hours of work, with a duration of 12.5 days and 1 resource unit.

Scenario 3: Changing task type to fixed-duration

Finally, let's say you make the same task a fixed-duration task. This means that the task must be completed in the duration you specify. Again, the task has 1 full-time person available for 8 hours a day, and it has a 10-day duration with 80 hours of work.

What you change

What Project does

Add a full-time resource

Project recalculates the work assigned to each resource. When just 1 person was assigned to the task, that resource had 80 hours of work to complete. When you assign another person to the task, each resource has 40 hours of work to complete over the same 10-day duration, for a total of 80 hours of work. By adding another resource unit, you also revise the allocation of both units to 50%, making them both available to work 50% on other tasks.

Increase the duration

If you have 8 days to complete the task rather than 10, Project recalculates the task's work. The task now has an 8-day duration, with 64 hours of work, and 1 resource unit.

Change the work

If, the task will take 20 hours of additional work, Project recalculates the task's resource units, so that the additional work can still be completed within the 10-day duration. The task now has 100 hours of work, with a duration of 10 days and 1.25 resource units. The resource unit that is currently assigned to the task is over allocated at 125%. You need to assign another person to the task to account for the additional 25% allocation.

Note: Because assignments of cost resources don't have values for work or units, these values will not be recalculated when the task's start date or finish date is modified. Dates are also never recalculated for a cost resource assignment, because you can’t modify the work or units.

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