Breaking Down the Critical Path Method (CPM) in Project Management

In the world of complex projects, delivering on time is a must.

After all, missing deadlines is like wearing a neon sign that says unreliable to clients. To ensure success, adopting a realistic and meticulous planning approach is crucial.

You may not have superhuman capabilities, but you have the critical path method.

This powerful technique can help you supercharge your project management by precisely analyzing task dependencies and critical sequences! 💥

This article explains the critical path method, its benefits, use cases, and main elements. It’ll also provide step-by-step guidelines and suggest some helpful project management software to make implementing the critical path method easier, even for beginners.

What Is the Critical Path Method?

The critical path method is a series or sequence of must-do tasks determining the project’s overall timeline. We call such tasks critical activities, and they’re essential for the successful and timely execution of a project. ⏲️

The critical path method, also known as critical path analysis (CPA), is a technique project managers use to form accurate schedules across the entire project. They do so by identifying critical dependent tasks by calculating their duration using a specialized formula (or critical path algorithm).

Easily see the critical path timeline, schedule, and activities in the customizable drag-and-drop Gantt chart view in ClickUp

They also often use Gantt charts or other diagrams to visualize and better understand the project timeline . Project managers use this to get a complete bird’s-eye view of the entire project and its dependent tasks to make better decisions.

The method was developed in the 1950s by Remington Rand’s James E. Kelley and DuPont’s Morgan R. Walker, who were looking to cut costs associated with inefficient scheduling. The pair also invented the Program Evaluation and Review Technique (PERT), a similar method often used alongside the critical path method.

Critical path medod vs. PERT

CPM and PERT are both project management methodologies for planning and scheduling. Unlike CPM, which is a deterministic model, PERT is probabilistic, meaning it considers a range of possible durations for each task to provide a more flexible timeline estimation.

To delve deeper into their differences, refer to the table below:

Benefits of Using the Critical Path Method in Project Management

Project managers will find many benefits to using the critical path method, including:

1. Accurate estimation: Thanks to the critical path method, you can make predictions, set realistic expectations, and successfully plan the rest of the project
2. Effective planning: Easily create a well-structured, realistic, and adaptable critical path project schedule and prevent major setbacks toward project completion
3. Task prioritization: Critical path method helps you identify critical tasks that need to be at the top of your priority list
   5. Improved communication: With a defined, visualized schedule, it’s easier to ensure everyone’s on the same page, which contributes to a smoother workflow

When to Use the Critical Path Method

Critical path analysis should happen at the beginning of the project lifecycle. It’s typically performed in the planning stage before scheduling. In some cases, project managers carry this out even earlier and included it in the project proposal .

Easily build out your project proposal with ClickUp Whiteboards to visually see every step or phase of the project

Industries that deal with complex projects, such as construction , engineering, and event planning, are the ones that benefit most from the critical path method. Besides projects involving many moving parts, the critical path method can also be helpful when it comes to time- or resource-constrained projects . 🚨

Key Components of the Critical Path Method

Before we start exploring CPM step-by-step, let’s learn its main concepts and their meaning. Think of the next section as your critical path method glossary! 📖

Project activities

In CPM, activities can be critical or non-critical. Critical activities are those you identify as important and include in the critical path. Non-critical project activities are all other tasks. They are less time-sensitive or essential, giving you more flexibility in scheduling.

Here’s a simplified example: If your project is to build a house, laying the foundation and installing the roof would be considered critical activities, while interior decoration would fall into the non-critical category. 🏠

Task dependencies

Activities have their relationships, i.e., dependencies. What that means is that they have to happen in a specific order. For instance, some dependent tasks have to finish before others can start, or they have to start simultaneously.

To continue with our house-building example—you can’t start furnishing a room until you’ve finished the flooring and the wall paint has fully dried. 🛋️

Network critical path diagram

The network critical path diagram is a flowchart for visualizing your project’s timeline and task dependencies. It consists of nodes, which are usually represented with rectangles or circles, and connectors, i.e., arrows.

Visualizing the structure of activities this way makes it easier to understand and identify the critical activities. A critical path diagram sometimes highlights areas in different colors to stand out from the non-critical task sequences.

You can also use Gantt charts and PERT charts to visualize your project timeline and critical paths, but more on that in the how-to section! 👀

Formulas and metrics

The critical path method consists of a series of calculations to determine the duration of tasks and the critical path. The primary metrics are:

1. Earliest start time (ES): The earliest possible date you can start an activity considering the dependencies
2. Earliest finish time (EF): The earliest possible date you can complete an activity considering its ES and duration
3. Latest start time (LS): The last possible date you can start an activity before causing a significant project delay
4. Latest finish time (LF): The latest possible date you can complete a task based on its LF and duration
5. Task duration (t): The total amount of time it takes to complete an activity

The critical path formula has two parts, which we’ll explain below.

Forward pass

We use the forward pass to calculate the ES and EF.

The ES of the first activity on any path will always be 1 since it indicates the start, i.e., the first day of your project.

The ES of all other activities equals the earliest endpoint of the preceding activity plus 1:

ES = EF of preceding activity + 1

The EF equals the sum of ES and the duration of the activity minus 1:

EF = ES + t – 1

Backward pass

With the backward pass, we calculate the LS and LF.

The LF of the last activity on any path will always be the same, as it indicates the end, i.e., the last day of the project.

The LS of an activity equals the difference between LF and the duration of the task plus 1:

LS = LF – t + 1

The LF of an activity equals the LS of the succeeding activity minus 1:

LF = LS of succeeding activity – 1

Float/Slack

The float or slack represents how long a non-critical task can be delayed without affecting the entire project timeline. Critical tasks don’t allow delays, so their float score is automatically 0.

There are two types of float:

1. Total float: The amount of delay that doesn’t affect the project completion date (LS or LF – ES or EF)
2. Free float: The amount of delay that doesn’t affect the start date of the succeeding task (ES of succeeding activity – EF of current activity)

How To Calculate the Critical Path in Project Management

Now that you’ve mastered all the elements of the critical path method, it’s time to put your knowledge to the test. In this section, we’ll show you how to calculate your project’s critical path in six steps. 🧮

Sort, filter, or group tasks for better visibility in a ClickUp List

Pro tip: If you opt for a project management tool like ClickUp , you can spare yourself from the manual and repetitive work. Instead of starting from scratch, use the pre-built ClickUp Critical Pathway Analysis Template .

With numerous task management features and intuitive Gantt charts, this tool makes CPM more accessible and streamlined! 🙌

Step 1: Create a list of tasks

The first thing you should do is determine the project scope. Collect all your activities in one place and define your goals, budget, and deadline.

List all tasks in a project to determine its scope

ClickUp’s List View provides you with the perfect framework for that. It’s a spreadsheet in which you can list all the tasks, subtasks, and relevant information about them in custom fields, such as:

• Start and due dates
• Duration
• Responsible department
• Accompanying documents

Feel free to add other custom fields to aid your project planning. You have over 20 field types at your disposal, including dropdown, checkbox, rating, and progress bar.

Besides listing tasks, you can also assign them, attach files, and lead discussions with your team in the comments.

Customize your project management system by arranging columns to suit your preferences like status, assignee, priorities, and more

Not a fan of spreadsheets and lists? Project managers can do everything in a Kanban-style ClickUp Board view as well to stay on top of the project schedule, uncover resource constraints, and see actual progress toward project completion.

Step 2: Define task dependencies

Accurate identification of dependencies is crucial for successful time estimation and planning. Discuss with your team and use your previous experience to figure out the most logical order of tasks.

To define task relationships in ClickUp, right-click on a task and select the Dependencies option. You can choose between three types:

1. Waiting on: Tasks that must be completed before the selected task
2. Blocking: Tasks that can’t start before the selected task has been completed
3. Related: Tasks that are related but not dependent on the selected task

Come up with the ideal order of tasks

Defining relationships is even easier in Gantt view. You only need to select the point on either side of the taskbar and drag it over to the corresponding point on the other task.

The best part is—this view allows you to automatically reschedule dependent tasks. To activate it, open the Show dropdown menu and toggle on the Reschedule Dependencies option.

Step 3: Visualize

Use a network diagram, work breakdown structure (WBS) , PERT chart , or any other visualization method to make the complex project task structure more comprehensible. Draw the flowchart and arrange tasks based on their chronological order and dependencies.

Make your project timeline easier to grasp with a network diagram, ClickUp’s Gantt chart, or another method

You can use pen and paper, a text editing or drawing program, or project management software like ClickUp. ClickUp’s Whiteboard View lets you brainstorm and collaborate with your team on decisions. You can create good-looking WBS or PERT charts in no time. Use shapes and connectors to create the structure. Add additional elements like images and docs to make the diagram more informative.

As per usual, you can start with a template to save time. ClickUp has many ready-made frameworks for you to use, such as this universal ClickUp PERT Chart Template or the ClickUp Simple PERT Chart Template .

Although different in terms of structure, Gantt charts are also a convenient way to envision the sequence of tasks in a project and estimate their duration. In ClickUp, Gantt charts are interactive and adaptable. They enable you to draw the roadmap and schedule tasks simultaneously in only a few clicks.

Step 4: Estimate the task duration

The next step is to define the t for each task, i.e., how many days it will take to complete it. Estimate based on your experience, historical data, and industry standards. Consult others, particularly experts, to gain multiple perspectives and make the most accurate predictions.

Input the information in the designated fields in List View or update it directly in Gantt view by resizing the taskbars.

Step 5: Identify the critical path

Discover the longest sequence of critical activities and how much leeway you have with non-critical ones

Using the formulas we shared earlier, calculate the ES, LS, EF, LF, and slack. Begin with the first task, which has a start time of 1, then define the EF and LF based on its duration. Repeat the same for all other tasks.

The longest sequence of critical activities (those that have 0 slack) is your critical path . You can also have multiple critical paths.

These calculations are much more manageable with ClickUp Gantt View . In your project Gantt chart , choose the Show option again, but this time, enable Critical Path and/or Slack Time .

The critical path will show up with a different color scheme, highlighting tasks with the blocking dependency in red. 🛑

With the Slack Time option enabled, a purple striped bar will appear alongside non-critical activities to depict the wiggle room they allow for. 🟣

Another way to discern critical from non-critical tasks is by adding priority tags and color codes. For instance, you can assign critical activities with a high-priority tag and non-critical activities with a low-priority tag, and the software will color them accordingly.

Step 6: Execute and revise

Finally, start bringing your project to life task-by-task. 🧱

As you go through tasks, you might realize some aren’t necessary or run into unexpected resource constraints. The delay caused by such events is called the critical path drag.

Monitor activities closely to ensure adherence to the schedule and catch any plan changes in time.

Use ClickUp’s Goal Tracking feature to stay on track to hit your goals with clear timelines, measurable targets, and automated progress tracking

In ClickUp, you can ClickUp Goals and automatically track progress. Choose between task, numerical, monetary, and True/False targets, then manage them all in one place. By closely monitoring your targets and progress, you can ensure your project stays on the right path at all times. 🛣️

Example of Critical Path Analysis

Remember our house-building example from earlier? Let’s expand on it! We’ll show you how to apply the critical path analysis to a real-life example.

We’ll be using the same ClickUp Critical Pathway Analysis Template.

Listing all tasks, along with due dates, assignees, documents, and other important info in the ClickUp Critical Pathway Analysis Template

Let’s start by listing all the tasks we need to take to build a house:

1. Planning and design
2. Site preparation
3. Foundation construction
4. Framing and structural work
5. Installations
6. Painting
7. Furnishing
8. Landscaping

We’ll also jot down the subtasks. For instance, in the planning and design stage, those would include:

1. Hiring an architect
2. Determining the house layout

3. Acquiring all the permits

   We’ll also define the project’s desired start and end date—May 18 to Mar 5.

Creating a diagram of the timeline with the ClickUp PERT Chart Template

Next, we’ll create a diagram in Whiteboard View. We’ll use the ClickUp PERT Chart Template to get a head start. Considering the dependencies and allotting larger shapes to tasks that require the longest time, we’ll create the flowchart to visualize the work ahead.

Finishing the diagram, paying attention to parallel tasks and other dependencies

Notice how the steps fork out after the Installations step? This is to indicate that:

• Exterior painting can happen at any point after the installations
• Interior painting can’t take place until the installations have been completed
• Interior and exterior painting can be performed simultaneously, which means these tasks are parallel
• Furnishing can’t happen until the interior paint job has dried
• The landscaping stage can’t start until the exterior paint job has dried

After completing the diagram, display the dependencies in your List or Gantt View.

Estimate the duration of each activity and form a realistic schedule with the help of a Gantt chart

Next, we’ll estimate the duration of tasks, writing the number of days in the designated field in List View. Considering that information, we’ll schedule tasks and/or subtasks in Gantt View.

Identify the critical path of the project and define the slack for flexible, non-critical activities

Finally, we’ll calculate the critical path and slack. In our case, there’s little leeway since most activities are crucial.

As you can see in the image above, the only task with slack is the exterior painting. Once the installations are completed, exterior painting can occur at any point, provided enough time is allotted to drying and, eventually, landscaping.

Say there’s been a change of plans, and our flooring contractors asked to reschedule for the following week. In that case, we’ll move the subtask bar to its new spot. With the automatic rescheduling option activated, the other tasks will be updated accordingly! ✔️

Navigate Project Timelines Like a Pro With the Critical Path Method

The critical path method can be an excellent helping hand when dealing with a demanding project. It enables you to meticulously assess and sequence tasks, ensuring that you meet deadlines, keep the project schedule in order, maintain healthy client relationships, and drive actual progress and growth.

When your tasks are sorted out, the rest of the project falls into place.

With a tool like ClickUp , you can try CPM for free and with minimal effort. Get started today! ✨