Duration type in Primavera P6

In Primavera P6, Duration Type is a setting that specifies how the software should calculate the duration of an activity. This setting is important for forecasting the behaviour of both activity duration and units. Primavera P6 uses two formulas to determine work units:

Resource units = Resource units per time unit * Duration

Remaining resource units = Resource units per time unit * Remaining duration

Depending on the duration type selected, one or two elements of the equation can be fixed and Primavera P6 will calculate the remaining elements. To determine which elements of the formula to fix, the nature of the work, the information available, the progress update method and the objective of the schedule must be considered. There are four activity duration types.

1. Fixed duration and units

This activity duration type is used in Primavera P6 when the duration and the quantity of resources are known and are expected to remain fixed in the schedule. With this configuration, the duration does not change when resources are added or removed, or when Units/Time are modified. A change in Duration will change Units/Time, but Units remain unchanged.

2. Fixed duration and units/time

This activity duration type is used in Primavera P6 when the duration and the productivity, or Units/Time, of the resources are known and must remain fixed. With this configuration, the duration does not change when resources are added or removed, or when Units/Time change. A change in Duration will change Units; however, Units/Time remains unchanged.

Primavera will keep the duration of the activities and increase the work, or units, and therefore the budget, based on the additional quantities of work performed. Units/Time.

3. Fixed units

This activity duration type is used in Primavera P6 when the quantity of work required to complete an activity is fixed. For example, excavating 50,000 m3 of earth. With this configuration, a change in Units/Time or Units causes the activity duration to vary. However, if the user updates the duration, the units remain unchanged and Units/Time varies. This activity duration type is recommended when duration depends on resources.

4. Fixed units/time

This activity duration type is used in Primavera P6 when the activity has fixed productivity per time period, regardless of the activity duration. With this configuration, resource units per time remain unchanged while the activity duration or units change.

User preferences

When assigning resources to an activity in Primavera P6, several resource assignment settings must be considered. The resource assignment calculation setting in User Preferences will affect how activity duration, units and units/time are distributed as additional resources are added. These calculation settings can be adjusted by selecting Edit > User Preferences activity duration types in primavera p6.

When Preserve the Units, Duration, and Units/Time for existing assignments is enabled, when resources are assigned to an activity, the duration remains constant and the units are calculated using the following formula:

Units = Duration * Units/Time

When Recalculate the Units, Duration and Units/Time for existing assignments based on the activity Duration Type is enabled, when resources are assigned to an activity, Primavera will keep one or more parameters fixed depending on the duration type assigned to that activity and recalculate the rest each time a new resource is assigned. For example, an activity with fixed units will modify the activity duration when more resources are assigned. By contrast, if the duration type is fixed duration and units, assigning new resources will modify each resource's units/time ratio and distribute the budgeted units among the resources.