You may have noticed the “Effort driven” option in the Task Details Form and wondered what it actually does.
Let’s break it down with a simple example.
Example Comparison
Task A – Effort Driven OFF
- This task does not have the Effort driven option enabled.
- When you assign 2 resources, each resource still has 80 hours of work.
- Adding more resources does not reduce the workload per resource or the task duration.
In this case, work increases as you add more resources:
- 2 resources = 160h total
- 1 resource = 80h total
Task B – Effort Driven ON
- This task has the Effort driven option enabled.
- When you assign 2 resources, the total work is shared:
- Each resource gets 40 hours
- Task duration is reduced (e.g., from 10 days to 5 days)
In this case, total work remains constant, but:
- Duration decreases as more resources are added
- Work is distributed across resources
Summary
Use the “Effort driven” option when the task duration can be shortened by adding more resources.
- Effort driven OFF → Work per resource stays the same, total work increases
- Effort driven ON → Fixed total work, shorter duration with more resources
Khuong Do Blog 
You can choose activity type “fixed work” and get the same result.
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Yes that’s correct. Fixed Work and Effort Driven mean the same thing in this context. In fact if you select Fixed Work, it automatically puts a tick in the effort driven check box and grey’s it out. :-). But you can have effort driven selected (or not) for Fixed duration and Fixed Unit tasks. In either of these cases the behaviour can be different.
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