Data Type Percentage/number (percentage/number field: A type of field whose content is a value that can be expressed as either a percentage or a decimal number. For example, in the Assignment Units field, one full-time assigned resource can be expressed as 100% or as 1.00.)
Entry Type Calculated or entered (calculated or entered field: A field in which the value is determined by Project based on information in other fields. Information that you enter in the field yourself overrides calculated values.)
Description The Max Units field contains the maximum percentage or number of units (units: The quantity of a resource assigned to a task. The maximum units is the maximum number of units available for the resource. For example, if you have three plumbers, the maximum units is 300 percent or three plumbers working full-time.) representing the maximum capacity for which a resource (resources: The people, equipment, and material that are used to complete tasks in a project.) is available to accomplish any tasks (task: An activity that has a beginning and an end. Project plans are made up of tasks.) during the current time period. The default for the Max Units field is 100 percent.
How Calculated If you have set the resource units in the Resource Information dialog box, this value is displayed in the Max Units field.
Best Uses Add the Max Units field to a resource view (resource view: A view that displays resource information. Resource views include the Resource Sheet, the Resource Graph, the Resource Usage, and the resource forms views.) when you want to display, filter (filter: Specifies which task or resource information should be displayed or highlighted in a view. For example, when you apply the Critical filter, only critical tasks are displayed.), or modify the maximum units (maximum units: The maximum percentage or number of units that a resource is available to be scheduled for any tasks. The maximum units value indicates the highest capacity at which the resource is available for work; the default value is 100 percent.) that a resource is available for work (work: For tasks, the total labor required to complete a task. For assignments, the amount of work to which a resource is assigned. For resources, the total amount of work to which a resource is assigned for all tasks. Work is different from task duration.) on any assigned task for the current time period. The Max Units field interacts with the Assignment Units field for an assignment (assignment: A specific resource that is assigned to a particular task.). If you assign a resource to more units than allowed by the Max Units field, Project will indicate that this resource is overallocated (overallocation: The result of assigning more tasks to a resource than the resource can accomplish in the working time available.). If a resource's unit availability (unit availability: Amount of time, expressed as a percentage or a decimal number, that a resource can be scheduled for assigned work. It refers to the availability of a resource; for example, a resource may be available 50%, 100%, or 300% of full time.) varies throughout the life of the project, also add the Available From and Available To fields to show the date range this unit availability applies to.
Examples Sean is working half-time on your project, and half-time on another group's project, so you set Sean's Max Units field to 50 percent. Later, you inadvertently assign Sean to a task at a unit of 100 percent. Sean is now overallocated (overallocation: The result of assigning more tasks to a resource than the resource can accomplish in the working time available.).
A new resource, Ashley, is starting work on this project about a month from now on June 1. Ashley will start the project working half-time, and then on September 1, Ashley will go to 75 percent. On January 1, Ashley will be 100 percent on the project. You use the Resource Information dialog box to set the availability (availability: Indicates when and how much of a resource's time can be scheduled for assigned work. Availability is determined by project and resource calendars, resource start and finish dates, or the level at which the resource is available for work.) dates and their corresponding units. You then add the Available From, Available To, and Max Units fields to the resource view so you can always see Ashley's availability for the current time period.
Remarks If a resource is assigned to more assignment units than the maximum units for all assigned tasks, the resource is overallocated, and the Overallocated field is set to Yes.
You can also specify maximum units in the Resource Information dialog box. This is also where you can set the different unit availability for different time periods throughout the project.
You can switch between percentages and decimals for representing maximum units in the Project Options dialog box.