How calculate duration in primavera P6.

Introduction

Primavera P6 is one of the leading project management software tools used globally for managing large-scale and complex projects. Among its many powerful features is its ability to calculate durations for various project activities. Properly calculating durations is crucial because the accuracy of your project schedule, resource allocation, and cost estimations all hinge on it. This article will walk you through the process of calculating duration in Primavera P6, offering a detailed explanation and practical, real-life examples.

What is Duration in Project Management?

In project management, duration refers to the total time required to complete an activity or task, measured in working hours, days, weeks, or months. It’s the difference between the start date and finish date of a task, excluding non-working days or times (like weekends or holidays).

Primavera P6 provides users with multiple ways to define and calculate duration, making it an essential tool for project managers who need to ensure that their schedules are as accurate as possible.

Types of Durations in Primavera P6

Before we dive into how to calculate duration in Primavera P6, it’s important to understand the types of durations available:

1. Original Duration (OD): The estimated time initially required to complete an activity. This is typically input manually by the user.
2. Remaining Duration (RD): The time remaining to complete an activity that has already started. Primavera P6 calculates this based on the percentage completion of the activity.
3. Actual Duration (AD): The actual time spent on completing an activity once it is finished.
4. Planned Duration (PD): The duration Primavera P6 uses to calculate the project schedule based on the current baseline.
5. Elapsed Duration (ED): Refers to the actual time passed (calendar time) since the start of an activity. It includes both working and non-working times.

Step-by-Step Guide to Calculating Duration in Primavera P6

1. Input Activity Information

The first step in Primavera P6 is to input activities into the project schedule. These activities can vary depending on the type of project you’re managing. For instance, in a construction project, activities might include excavation, foundation laying, and concrete pouring.

To do this:

• Open Primavera P6 and navigate to the Activities tab.
• Define each activity by entering key information such as the activity name, activity ID, and duration type.

2. Define Calendar for the Project

Primavera P6 allows you to define calendars that specify the working hours, holidays, and non-working days. This is important because the calendar affects the total working time available for the project. Calculating accurate durations depends on whether you’re working with a standard 5-day workweek, a 7-day workweek, or any other custom schedule.

• Navigate to the Enterprise menu and select Calendars.
• Choose an existing calendar or create a new one that reflects the working schedule of your project.
• Define the workdays and non-working days (holidays or weekends) that impact the duration calculation.

Example: In a construction project where workers only work Monday to Friday, excluding public holidays, the project calendar should reflect this to ensure accurate duration calculations.

3. Assign Duration Type

Primavera P6 allows users to choose between four different duration types that affect how the duration is calculated:

• Fixed Duration & Units: The duration remains constant, and resource units are calculated based on available resources.
• Fixed Units: The number of resource units is fixed, and the duration is calculated based on the work required.
• Fixed Units/Time: Both the number of resource units and the units/time (e.g., work per day) are fixed, and the duration is calculated automatically.
• Fixed Duration & Units/Time: Both the duration and units/time are fixed, and Primavera P6 calculates the total resource units.

Example: In a software development project, you might have a team of developers working for 8 hours a day (fixed units/time). You estimate the task will take 5 days, so you choose “Fixed Duration & Units/Time” as the duration type.

4. Enter the Duration

You can manually enter the estimated duration of each task based on historical data or expert judgment. Primavera P6 offers two fields for entering durations: Planned Duration and Remaining Duration.

To enter or adjust durations:

• Select the activity in the Activities window.
• In the General tab, enter the planned duration in the Planned Duration field.
• If the activity is ongoing, enter the remaining duration in the Remaining Duration field.

Example: For a manufacturing task in a factory, if you know that the task of assembling a machine usually takes 10 working days based on past projects, you would input “10 days” into the Planned Duration field.

5. Link Activities with Dependencies

To create an accurate project schedule, it’s essential to link activities using relationships such as finish-to-start (FS), start-to-start (SS), finish-to-finish (FF), or start-to-finish (SF). These dependencies influence how durations are calculated since some activities might need to start or finish in conjunction with others.

• Highlight an activity.
• In the Predecessors or Successors tab, define the logical relationships between activities.

Example: In a construction project, the activity “Start Framing” cannot begin until “Foundation Completed” has finished, creating a finish-to-start dependency.

6. Adjust for Lag or Lead Time

Primavera P6 allows you to add lag or lead time between activities. This is the time delay (lag) or overlap (lead) between dependent activities. Lag can add days to the duration, while lead allows for overlap between tasks.

• In the Predecessors or Successors tab, add the necessary lag or lead times.

Example: In a civil engineering project, after pouring concrete, there is a mandatory 3-day curing time before further work can commence. This 3-day delay should be added as lag between “Concrete Pouring” and the next activity.

7. Update and Track Duration as Work Progresses

As work progresses, you should update the schedule to reflect actual conditions on the ground. If an activity takes longer than expected, you need to adjust the remaining duration. Primavera P6 allows you to track this by:

• Marking activities as started or completed.
• Entering the percentage of work completed.
• Adjusting the Remaining Duration based on progress.

Example: In an IT implementation project, if the “Server Configuration” task was expected to take 5 days but is 60% complete after 3 days, you can estimate that 2 more days remain. You would then update the remaining duration to reflect this.

8. Recalculate the Project Schedule

Once you’ve entered durations, dependencies, and any lag or lead times, you can let Primavera P6 calculate the overall project schedule. The software uses a scheduling algorithm based on the critical path method (CPM) to determine the total project duration and identify which activities are critical to the project’s completion.

• Go to the Tools menu and select Schedule.
• Primavera P6 will recalculate all activity durations and update the project timeline based on the input data.

9. Check for Critical Path and Float

After calculating durations, Primavera P6 identifies the project’s critical path. The critical path is the sequence of tasks that must be completed on time for the project to finish as scheduled. Any delay in a critical path activity will delay the project.

Activities not on the critical path have “float,” or extra time they can be delayed without affecting the project’s completion.

Example: In a road construction project, the activity “Paving the Road” might be on the critical path because any delay here would push back the project completion date. On the other hand, “Landscaping” might have 5 days of float, meaning it can start a few days late without impacting the overall schedule.

Real-Life Application: Example of Duration Calculation in Primavera P6

Let’s look at a real-life scenario to understand how to apply these concepts.

Scenario: You are managing a residential building construction project. The project has five key activities:

1. Excavation: 5 days
2. Foundation: 7 days (Starts after Excavation)
3. Framing: 10 days (Starts after Foundation)
4. Roofing: 5 days (Starts after Framing)
5. Landscaping: 7 days (Can overlap with Roofing)

Steps in Primavera P6:

1. Input activities and assign durations: Excavation (5 days), Foundation (7 days), etc.
2. Define a 6-day workweek calendar to account for weekend work.
3. Create finish-to-start dependencies for sequential tasks and start-to-start relationships between Roofing and Landscaping.
4. Add a 1-day lag after the Foundation for concrete curing.
5. Update and track progress as work begins. For example, if Excavation takes 6 days instead of 5, update the Remaining Duration and recalculate the project timeline.

By following this workflow, Primavera P6 recalculates the overall project duration, identifies the critical path, and provides you with an updated schedule.

Conclusion

Calculating durations in Primavera P6 is not just about entering a few numbers—it’s about understanding the relationships between activities, applying real-world constraints like work schedules and resource availability, and continuously tracking progress. By following the steps outlined

in this guide, you can create a highly accurate project schedule that reflects the true duration of tasks, keeping your project on track and under control.

Mastering duration calculation in Primavera P6 is essential for ensuring project success, especially in complex projects where even minor miscalculations can lead to costly delays. With practice, this powerful tool can become a cornerstone of your project management process.