The Critical Path Activities on a Project

Aug 7, 2019 | Project Management

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Photographer: Lou Levit | Source: Unsplash

Every project features some activities that are crucial for timely completion. These are called critical activities. Determination of critical activities is a project modeling technique. Identification of these activities makes it easier for management to identify which areas require more attention and resources on a priority basis and which ones can be put on hold.

In this blog post, we take a brief look at why critical activities matter and how they should be handled by project managers.

Understanding Critical Path

The critical path outlines the longest distance between the start and the end of a project. It includes all the tasks, resources, and activities that must be completed to finish the project on time. The critical path also forms the basis of the project schedule and indicates the time it would take to complete the work.

There are a few terms used in critical path modeling that make it easier to understand how this model works.

Earliest Start Date

This is the earliest date at which an activity can begin. Most projects have many activities that take place successively, one after the other. An activity that is dependent on the completion of a previous task is generally given the earliest start day based on the time it would take to complete the preceding activity.

Earliest Finish Date

The earliest finish date is the minimum amount of time it would take to complete an activity. In most cases, it is understood that the activity must receive full attention and resources from the project in order to meet its earliest finish date.

Latest Start Date

The latest start date is the latest date by which an activity can start due to delays in prior tasks. It identifies the date by which the activity must start before it threatens the project’s timeline. Latest start dates are particularly important for earlier activities on a project because later activities are dependent on their timely completion.

Latest Finish Date

This is the latest finish date for a particular project activity. Delays in the completion of activities, particularly the earlier activities, can push the project off-schedule significantly and make it difficult to complete on time.


Every activity on the project has a float that determines how long that task can be delayed before it has an impact on the project schedule. The float is calculated by subtracting the earliest start date from the latest start date or the latest finish date from the earliest finish date on the project.

The float for critical path activities is zero on a project.


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Photographer: ROOM | Source: Unsplash

Every project activity has a crash period which is the shortest amount of time required to complete the task. In order to crash complete a task, the project manager has to shift resources and more project members to the task.

Crash completing a task can reduce the quality of output. However, there is usually a direct relationship between the resources dedicated to the task and the time it takes to complete the activity.

Setting Up a Critical Path

The project manager can use a variety of techniques for identifying the critical path for a project but it basically comes down to four steps.

1. Identify all the work that is required to complete the project and break it down into distinct activities. You can carry out a project breakdown model that divides the project into different phases, noting down every deliverable for the project.

2. Calculate the duration of each task, assessing how much time it would take to complete it before moving on to the next phase. It can be difficult to identify the exact time to complete a task and project managers make a rough estimate of expected activity time. For example, a project manager may calculate that an activity will be completed in 10 – 14 days.

3. If some of the later activities are dependent on the completion of prior tasks, a task dependency schedule must be created that outlines when new tasks can start. The schedule must create and show links between different project activities and how they relate to one another.

4. The major project milestones must be identified. These milestones highlight the completion of project activities and show how one task moves to the next after the conclusion.

Once you have outlined the tasks in a schedule chart, look at the float for each one. Activities with a positive float mean they can be delayed for the float duration without any delays on the delivery time.

There will be a set of successive activities that have the longest completion time and zero float. This set of activities is called the critical path activities.

Benefits of Identifying & Using the Critical Path

The critical path allows the project manager to identify tasks that cannot be given flexibility in completion time. Some activities on projects have a certain amount of “float” time. These can be extended or delayed without having an impact on the project schedule.

Visualizing the critical path method is key for creating an accurate project baseline. By outlining the project sequence you can better understand and anticipate the ES (earliest start), LS (latest start), EF (Earliest finish), and LF (Latest finish) dates of a project. To do this, you will need to sequence events based on due-dates and dependencies. This part of the CPM is called creating a Path. Paths are best viewed as a Gantt chart. You can either create a Gantt chart from scratch or use project management automation software like to create one for you.

It is important to remember that activities on the critical path have zero float. A delay in the critical path activities can cause a delay in the overall project delivery. The only way to complete the project on time is if some of the critical tasks can be crash-completed through resource allocation.

For some projects, it is very important to monitor the critical path activities to ensure that the project is delivered on time. This type of project management approach is called the critical path project management. The method is quite common for construction projects, new product launches, or software development where deadlines are strict and activity duration can be estimated to a level of certainty.

A competent project manager must have a thorough understanding of the critical path method so that they can evaluate the effects of potential activity delays on overall project completion time.

To learn more about project management and critical path activities, subscribe to our courses at or get in touch with us by filling out this form!

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