Duration decreases when asign more than one work resource

Copper Contributor

I have a problem with project, when asign more than one work resource to a fixed units task, the duration is decreased by project. It did not happen before.


It reduce duration! it shouldnt do that the duration should have been the same.

How can I fix this problem????

Thanks in advance for your help


6 Replies
Hola Luis
The Type of task that maintains the Duration of the task when increasing its number of resources is Fixed Duration (Duración fija).
The Fixed Units (Unidades fijas) task type is used to maintain the number of Resource Units assigned to the task when the user changes the Duration of the task or the amount of Work of the resources in the task.
Let me add one more thing to Ignacio's response. Project schedules using what is called a work equation.
Duration = work/units
Where duration is the time span for performing the task
Work is the effort required by one or more resources to complete the task
Units is the number of resources expressed as a percent or decimal value

The type of task (fixed units, fixed work, or fixed duration) determines which of the variables in the work equation remains constant while the other two variables vary.

Thanks Ingnacio and Jhon, yes you have described very clear the behavior of ech type of task, fixed work, fixed units and fixed Duration. The case is, if I have a fixed units task with ten days duration, and assign one work resource (100%), then the ten day does not change and Project assign 8 work hours a day for each of the ten days, thats ok. But when I assign two work resources (200%) it should assign both resources for the ten days and program 16 work hours each of the ten days, instead of that, it reduces duration to five days and assign 16 work hours each day but just for five days. This is not the way Project use to handle Fixed units task.
Any suggesstion?


How exctly are you assigning the resources?


Here is a fixed units task (not effort driven). One resource is assigned at 100%:


Now I assign a second resource. The total work is doubled but the duration remains at 10 days with each resource working a normal 8 hr day.


If the task is switched to effort driven before the second resource is assigned, when the second resource is assigned, the added effort reduces the duration to 5 days. Both resources are still at 8 hrs per day.


John (not Jhon)


Hello Luis.

I think it always worked the same way, although it still seems like strange behavior to me, given that, as Jhon points out, that's what the Conditioned by Effort option is for, and it is not being considered.

In a Fixed Units task, regardless of whether or not it is conditioned by effort, I believe that the duration has always been reduced by increasing the numerical value of the assigned Units.

Another issue is that if in that same scenario, instead of increasing the value of the units, you add a resource with a different name, and it is not selected conditional on effort, it does not reduce duration, and it does otherwise.

My suggestion is as I said initially, select Fixed Duration, increase the resources and then return to Fixed Units. Or if you prefer, as Jhon also says, use Manual mode and after increasing units, return to Autocheduling Mode.

Ignacio (no Ingnacio)


Again, it's John and not Jhon. I don't know, maybe Spanish translates differently.
You seem to infer that I pointed out the effort driven is "not being considered". My example shows that for a Fixed Units type task, the effort driven option IS considered when adding (or removing) resources.

Later you say I suggest using manual mode after increasing units and then switch back to auto-schedule mode. Sorry, I did NOT say that. I was simply trying to demonstrate the difference when effort driven is selected for a fixed unit type task.