About Duration Types

Duration type is the basis for estimating an activity's completion time. It determines whether the schedule, resource availability, or costs are most important when updating activities. The duration type applies only when you have at least one resource assigned to the activity. Select one of the following duration types based on which factor is most important (least flexible) in planning your project: Fixed Duration & Units/Time, Fixed Duration & Units, Fixed Units/Time, or Fixed Units.

Fixed Duration & Units/Time or Fixed Duration & Units: Indicate that the schedule is a limiting factor in your project. The activity's duration does not change regardless of the number of resources assigned when you modify or update activities. You usually select one of these duration types when you are using task-dependent activities. When you update the remaining duration for the activity, you can select to calculate either the remaining units or the units per timeperiod. The duration type enables you to control which variables of an equation are calculated when you change a value.
If you want to recalculate the remaining units and keep the units/time for the resource constant, select Fixed Duration & Units/Time. The application uses the equation: Remaining Units = Units/Time x Remaining Duration. For example, if a resource is assigned to an activity for 8 hours/day for 5 days, the remaining units or work is calculated as 40 hours.

If instead you want to keep the remaining units constant and recalculate the units/time, select Fixed Duration & Units. The application uses the equation: Units/Time = Remaining Units/Remaining Duration. For example, if a resource is assigned to work 40 hours in 5 days, the units/time is calculated as 8 hours/day.
Fixed Units/Time: Indicates that resource availability is the most critical aspect of your project. In this case, the units/time or rate of the resource remains constant, even if the activity's duration or work effort changes. You most often use this duration type when you are planning resource-dependent activities.
Fixed Units: Indicates that the budget (units or cost) is a limiting factor; that is, the total amount of work is fixed. When you update activities, the work effort required to complete the activity does not change, even if the activity's duration or the resource rate changes. Typically, you would use this type in conjunction with resource-dependent activities. Increasing resources can decrease the activity duration.

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