I'm a newbie to MS Project here, so I was wondering if someone could point me in the right direction, or tell me if I'm barking up the wrong tree.

Is there a way to constrain a resource in MS Project to where they are only expected to work 80% of the time on the project, and also no more than 50% on a given task in a given day? For example, in a 10-hour day, a resource can work on Task1 for 5 hours and then Task2 for three hours before starting the next day to work on Task1 again for 5 hours and then Task2 again.

Is this something that is possible? And if so, where would I look to configure such a rule? Would this be the difference in configuring the units to 80% on a specific resource, and then altering the units of the resource on the specific tasks to 50%?

Many thanks in advance for any input.

3 Answers 3


First off, try it out in Project. Create a small dummy project and see if it works.

In my limited testing, it doesn't look to produce the results you are expecting. Setting an 80% threshold on the resource and a 50% threshold on the task, still leads to over-allocation on days that overlap. You are telling project that the resource can only work 80% maximum, then on the task they are only going to work 50%, which just extends the task by 2x. When a task overlaps with another task, then that resource works 50% on one task and 50% on another task, breaking the 80% rule. You can go 40% on a task, but then will get the opposite problem on tasks that don't overlap.

It's possible to take another spin on this though. I used to be heavy into percentage resource allocation as it seemed to illicit the feeling of a more concrete estimate. I could talk to my stakeholders with numbers, which made it seem like we have really thought things through. It was easy to setup, but managing the progress was a nightmare and I just ended up fudging the numbers anyways.

A couple years ago I switched to focus more on deadlines, rather than what percentage of time are you going to put towards this. So in your example, rather than complicating the matter with different percentages, ask the resource when they will be done the work. Let them figure how the work you need done slots in against other priorities. This does two things, creates accountability for the resource as it is purely developed by them and produces an objective result that can be tracked. Updating your project each week now becomes just a matter of moving the progress bar and updating end date if required. I do this now for all my projects and have found that this approach increased success.


You can set values like the Max Units on resources in your Resource Sheet to 80%, and then set the Units of a resource assignment on a task to 50%, but I find MS Project's calculations in regards to units can leave users confused and are not always easy to make sense of. I recommend a different approach.

First, a best practice is to have resources in your resource sheet defined as roles or functions rather than individual people. See this question for more on that topic.

Second, you should plan tasks by scope and best estimated duration first, then worry about assigning resources. The duration of a given task can be dependent on many factors, not just the amount of resources you can put on it. You can also link tasks together to make sure you are meeting the deadline dates of your critical milestones, given your duration estimates, and revise as necessary. After this, you can get with your team to load resource assignments. It's generally much easier for teams to plan how many labor hours they would need to assign to a task given a pre-established duration, and you don't need to worry about messing with the unit percentages.

Note that scheduling is a very iterative process. Things are always subject to change in your file. Once you go through an initial round of resource loading, you may look at your resource profile and realize you need to make cuts or additions. You may decide you want to throw more resources at certain tasks in order to decrease their durations and see how it affects your schedule, etc.


To plan with a work time of maximum 80%, you need to define the column Max.units at 80% instead of 100% for every single resource in the resource sheet.

It is not possible to plan a maximum work time per resource and per task. The task could involve several resources, so a maximum allocation makes no sense for MS-Project. But you can consider a workaround and create a general task calendar (Project -> Change Work time -> Create new calendar). Define for this new calendar its general working hours to 50% of the normal work time (tab work weeks -> Details). You do this by setting reduced working hours (e.g. only mornings). Of course, this is only possible if you plan per day and not at hourly level. You then need to assign this special work calendar to every task in the task sheet.

With this setting, the work time per task is at maximum 50% per involved resource unless you manually override it. Assignments of more than 80% per day for a resource are spotted as overallocation and could be levelled with the usual way. It's not an ideal solution but a practical work around.

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