Critical Activity : Longest Path

Now ,when it comes to your project’s Critical Path monitoring and control, there are few topics more important to your client. The expectation is on the planner to know your project’s Critical Path inside and out.

Critical path definition :

The critical path is defined as the longest logical path through the CPM network and consists of those

activities that determine the shortest time for project completion. Activities within this or list form a series (or sequence) of logically connected activities that is called the critical path. A delay to the start or completion of any activity in this critical path results in a delay to project completion, assuming that this path consists of a continuous sequence of activities without an overriding date constraint or multiple calendars. (Source : AACE International Recommended Practice No. 49R-06)

Let's hear from PMI itself .

The critical path is the sequence of activities that represents the longest path
through a project, which determines the shortest possible project duration. The resulting early and late start and finish dates are not necessarily the project schedule, rather they indicate the time periods within which the activity could be executed, using the parameters entered in the schedule model for activity durations, logical relationships,
leads, lags, and other known constraints. The critical path method is used to calculate the amount of scheduling flexibility on the logical network paths within the schedule model. (Source : PMBOK 5th Edition).

In my experience, it makes sense to focus on a project’s Longest Path as it is definitely the path where deviations from plan will affect the project’s finish date or also known as Mechanical Completion Date. It is also my strong advise to know your project's longest path and monitor it.

What the client wants to see might be something else, but the timely completion of Longest Path activities leads to your project finishing on time.Most software packages in the market let you track both Critical Path and Longest Path. Monitor and control both.

How to monitor Critical path in Primavera P6?

Option 1.
Edit your columns and look for “Critcal” and a “Longest Path”. Add any of this or both to display the activity that satisfy the critical of "Critical" and "Longest path".

Turn on Filter

You can filter out the "Critical" or/and "Longest Path" activity.

Option 2 : (Personally, I often use this for presentation and report submission)

When you schedule a project, you can choose to calculate multiple critical float paths (sequences of activities) that affect the project schedule. By calculating multiple critical float paths, you can determine the most critical path in the project schedule, along with sub-critical paths that affect the completion of the most critical path.

To calculate multiple critical float paths for all open projects from the Projects > Activities page.

1.Open the project or group of projects you want to work with in the Projects section.
2.Click Activities on the Projects toolbar to display the Activities page.
3.On the Activities page, click Schedule on the Activities toolbar.
4.In the Schedule Project dialog box, click Scheduling Options, then click the Advanced tab.

When you set scheduling options from the Activities page, your selections apply to all open projects.
5.Mark the Calculate multiple float paths option.
6.Choose to calculate multiple paths using Total Float or Free Float.
7.In the Display multiple float paths ending with activity field, click Assign to choose the activity you want the float paths to end on. You can choose any activity; however, typically this activity is a milestone or some other major activity in the project schedule.
8.Specify the number of float paths you want to calculate. Type a low number (10 or less) to optimize performance.
9.Click Close.


On the project scheduling options Advanced tab, you can choose to calculate a specific number of critical float paths based on total float or free float. You can also choose the activity you want the float paths to end on. By choosing an activity, you can calculate multiple float paths that affect the entire project schedule, a specific part of the schedule, or a milestone in the schedule.


When you schedule the project, P6 Web Access identifies the most critical float path in the schedule and assigns those activities a Float Path value of 1. Then, depending on the number of paths you choose to calculate, P6 Web Access identifies other float paths (sub-critical float paths) that affect the most critical float path and numbers the paths in ascending order (beginning with 2) based on the criticality of the path.


After you schedule a project, you can display the Float Path and Float Path Order columns in the Activity Table on the Projects > Activities page. Group by Float Path to view the activities in each critical float path, then sort by Float Path Order to view the order in which the activities were processed.

Select your targeted activity. For instance is your project completion date or Mechanical Completion date.

After you schedule your activity, you can group by Float Path.

Later stage, you can sort by Float Path Order.

 As you can see, you will be able to figure out the string of activities that influencing the completion date of our activities that identifies earlier.

The longest path is calculated by first performing a CPM ‘forward pass’ to determine driving relationships and the project’s latest, early finish date. The activity (or activities) with the latest, early finish dates are then identified and all predecessor driving relationships traced back to the project start date. These activities constitute the project’s longest path.