Task duration vs completion date

Copper Contributor

Not currently a Project user as we haven't had many projects that justify its use, however we have some larger projects that we are using an Excel Gannt chart for but want something a bit more interactive, hence MS Project.

My question is we have individual tasks that may take around 10days to complete, however they are dependent on works outside our scope for completion. Meaning we can start the task but then may not be able to complete it for 60 or 90 days. Using Excel it looks like this task now takes 30days.

Without breaking the task down further, is it possible for both 'durations' to be documented in Project?



3 Replies


In Project terms you have two separate parameters, duration and work. Duration is the time span during which a task is performed. Work is the amount of effort expended by one or more resources to complete the task. In your case the "10 days" to complete is actually 80 hours of estimated work. The 60 or 90 days is the duration. Set the task as Fixed Duration and you will be able to "separate" the two parameters.


Hope this helps.


Thanks @John-project. I think I understand what you are saying. Do you have an example image of what this looks like?


Sure. Project has three task types, fixed work, fixed units (i.e. resources), and fixed duration. Project's scheduling engine uses the following equation:

Duration = Work/Units

The default task type is fixed work, so the number of units (resources) assigned drives the duration. With a fixed duration task, the time span (duration) is fixed and amount of work and resources are the variables.


Based on your example, the duration is set at 60 days and the work is set at 80h (assuming a normal 8/5 workweek). With those inputs, the single resource's assignment will be 17% of a normal full time employee. Project will automatically spread the 80 hours of work linearly over the full time span as shown in the lower pane (Task Usage view). Work hours can be manually edited within the full duration a selection of Work Contour's can be selected for the assignment (default contour is Flat).


Hope this helps.