Scheduling a project involves managing many tasks, deadlines and dependencies, which makes it a complex process. To handle this complexity, project managers use various project scheduling techniques to plan effectively. One of the most widely used and effective methods is critical path analysis. This technique helps identify the longest sequence of tasks that determine the minimum time needed to complete the project.
What Is Critical Path Analysis?
Critical path analysis is a project scheduling method that identifies the longest sequence of dependent tasks required to complete a project. It uses a critical path diagram to visually map tasks, their durations and dependencies, making it easier to analyze. The critical path is calculated by applying an algorithm that determines the earliest and latest start and finish times for each task based on their relationships.
This algorithm is at the heart of critical path analysis, enabling project managers to pinpoint the sequence of tasks with no slack that directly impacts the project’s finish date. The diagram and calculations work together to show which activities are critical and which have flexibility, allowing teams to make informed decisions, allocate resources wisely, and keep the project on track despite challenges.
Critical path analysis also aids in creating a Gantt chart. It identifies the sequence of tasks that directly affect the project’s completion date. By calculating the longest stretch of dependent activities with zero slack, project managers can determine which tasks must be prioritized to avoid delays. This analysis ensures that the Gantt chart highlights high-risk areas in the schedule, allowing teams to allocate resources strategically and make informed decisions about adjusting timelines or workloads. Including the critical path in a Gantt chart helps maintain control over the project and keeps it on schedule.
ProjectManager is award-winning project and portfolio management software featuring powerful Gantt charts that filter for the critical path, allowing you to focus on essential tasks. Our Gantts help with critical path analysis, but can also link all types of task dependencies to reflect real-world workflows.
Setting a baseline enables teams to track project variance in real-time by comparing planned timelines with actual progress. These features work together to give project managers a dynamic and accurate planning tool that goes beyond basic scheduling, helping them deliver projects on time and within scope. Get started with ProjectManager today for free.
Critical Path Analysis Steps
To perform a critical path analysis, you need to follow a series of clear steps. These help you organize tasks, calculate timings and visualize the critical path. Below are the main steps to implement this technique effectively so you can manage time, resources and priorities with greater confidence and control.
1. Create a Project Task List
The first step to implement critical path analysis is to create a detailed list of all project tasks. This ensures nothing is overlooked and every activity is accounted for in the schedule. Ideally, you should develop a work breakdown structure (WBS) beforehand, as it provides a clear, organized framework for identifying all deliverables and breaking them down into manageable tasks.
2. Estimate the Duration of Tasks and Identify Dependencies
Once you’ve identified all project tasks, the next step is to estimate the duration of each task and identify dependencies between them. Knowing how long each activity will take and which tasks rely on others helps build an accurate timeline. These estimates and dependencies form the foundation for calculating the critical path and constructing the project schedule.
There are four main types of task dependencies in project scheduling, each defining how tasks relate to each other:
- Finish-to-Start (FS): A task must finish before the next can start.
- Start-to-Start (SS): Two tasks can start at the same time.
- Finish-to-Finish (FF): Two tasks must finish at the same time.
- Start-to-Finish (SF): A task cannot finish until another starts.
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Critical Path Template
Use this free Critical Path Template for Excel to manage your projects better.
3. Draw a Critical Path Analysis Diagram
The critical path analysis diagram is a type of project network diagram that visually represents the sequence of tasks and their dependencies. It consists of nodes and arrows, where each node represents a specific task and arrows show the relationships between them. This diagram helps project managers see the flow of activities, understand task order and identify the longest path of dependent tasks that determine the project’s minimum completion time.
Each node in the diagram contains four key project scheduling values: earliest start (ES), earliest finish (EF), latest start (LS) and latest finish (LF).
- Earliest Start (ES): The earliest time a task can begin, based on the completion of its predecessor tasks.
- Earliest Finish (EF): The earliest time a task can be completed, calculated by adding its duration to the earliest start.
- Latest Start (LS): The latest time a task can begin without delaying the project’s overall completion.
- Latest Finish (LF): The latest time a task can be completed without impacting the project’s finish date.
These values are calculated using the critical path analysis algorithm, which performs forward and backward passes through the network. The algorithm computes ES and EF during the forward pass, then calculates LS and LF during the backward pass.
These calculations identify which tasks have no slack, meaning any delay to them delays the project, and which tasks have flexibility. Displaying these values within the nodes allows project managers to clearly see critical and non-critical tasks, plan resources efficiently and monitor progress against the schedule with confidence.
4. Calculate the Forward Pass
The forward pass is a mathematical calculation used to determine the earliest start (ES) and earliest finish (EF) for each task. Start at the first task in the network diagram and set its ES to zero.
Add the task duration to ES to find EF. Move to the next task, setting its ES to the largest EF of its immediate predecessors. Repeat this process through the diagram, always carrying forward the highest EF values to the following tasks until reaching the final node.
5. Calculate the Backward Pass
The backward pass calculates the latest start (LS) and latest finish (LF) for each task. Start at the final task and set its LF equal to the project’s total duration. Subtract the task duration from LF to find LS.
Move backward through the diagram, setting each task’s LF to the smallest LS of its immediate successors. Continue this process until reaching the first task, ensuring that you use the lowest LS values when multiple successors exist, which identifies tasks’ flexibility and criticality.
6. Identify the Critical Path of the Project
The next step is to calculate the slack (or float) of each task, which reveals the critical path of the project. Slack is the amount of time a task can be delayed without affecting the project’s completion date.
Tasks with zero slack are critical because any delay in these tasks will delay the entire project. By identifying tasks with zero slack, you can see the longest sequence of dependent tasks that defines the project’s minimum duration.
7. Estimate the Project Duration
After completing the forward and backward pass, each project task has an accurate estimation of its earliest and latest start and finish times. This information allows you to determine the overall project duration by adding the durations of the tasks on the critical path. The result is the shortest possible project timeline.
Critical Path Analysis Template
Download our critical path analysis template for Excel to help project managers create a critical path diagram and calculate the ES, EF, LS and LF values of project tasks. It comes with two task sequences, but can be adjusted to reflect the scope of any project.
Use this free template to identify the most crucial tasks in a project and understand how they impact the overall project timeline. By visualizing these tasks that have zero slack, project managers can better prioritize tasks, allocate resources and reduce delays.
Critical Path Analysis Example
Let’s bring everything together with a simple example to show how critical path analysis works in practice. This example will walk you through the main steps — from listing tasks and estimating their durations to identifying dependencies, drawing the diagram, running the calculations and finding the critical path — so you can see how it all fits together.
Imagine a construction firm tasked with building a house.
To keep the project on track and avoid costly delays, the team decides to use critical path analysis. They break the project into individual tasks, figure out how each task depends on the others and estimate how long each one will take. This example shows how the firm organizes its work and identifies the critical path to finish the house as efficiently as possible.
As mentioned above, the first step is to list project tasks, as shown in the table below.
The next step will be to draw a critical path analysis diagram, showing the task dependencies that make up two distinct task sequences for the execution of the project. These two task sequences will happen simultaneously.
The next step is to perform the forward pass calculation as previously explained. The first two tasks of the project are “Site Preparation” and “Obtain Permits.” As you can see, their earliest start (ES) is zero, because there are no preceding tasks. Their EF is calculated by adding their ES value and their estimated duration.
The same is done for the next tasks, “Lay Foundation” and “Order Materials.” Their earliest start (ES) is the (EF) of their preceding tasks, as shown below. Then, the EF is calculated by adding their ES value and their duration.
This forward pass process is conducted until the finish node is reached. After completing the calculations, the finish value will be revealed, which is the largest earliest finish (EF) value. This “Finish” value will be important to conduct the backward pass calculations.
Now, it’s time for the backward pass. The first step in the backward pass is to assign the “Finish” value, which in this case is 57, as the earliest finish (EF) for the tasks that are immediately next to the “Finish” node.
Then, the next step is to determine their latest start (LS) value by applying the formula “LF – task duration” as shown in the image below.
The same calculation is applied to all preceding tasks until the start node is reached.
Once these forward pass and backward pass calculations are done, the ES, EF, LS and LF values for each task will be established. The next step is to calculate the slack for each task by applying the formula:
Slack= (EF – LF)
The tasks with zero slack will reveal the critical path of the project. The final result should look like the critical path analysis diagram below.
As you can see, the critical path of the project is the task sequence that starts with “Site Preparation” and ends with “Roofing”.
Advantages of Critical Path Analysis
Critical path analysis is a key project management technique used to identify the longest sequence of dependent tasks that determine a project’s duration. By focusing on these critical tasks, teams can optimize planning, avoid delays and ensure successful delivery. Below are the key advantages of using critical path analysis:
- Highlights the most important tasks that directly impact project completion
- Improves scheduling accuracy and timeline forecasting
- Helps allocate resources more efficiently by focusing on high-priority activities
- Enables better risk management by identifying potential bottlenecks early
- Supports proactive decision-making and faster issue resolution
- Enhances communication by clarifying task dependencies and priorities
- Allows for more effective monitoring and control of project progress
Disadvantages of Critical Path Analysis
While critical path analysis is a valuable tool for managing complex projects, it also comes with certain limitations. These drawbacks can affect accuracy and flexibility if not addressed properly during planning and execution. Below are some of the key disadvantages of using critical path analysis:
- Can become overly complex for large or dynamic projects with many tasks
- Requires accurate time estimates, which are often difficult to predict
- Doesn’t account for resource availability or constraints by default
- May not reflect changes in real time without ongoing updates
- Focuses only on task duration and dependencies, not task quality or cost
- Relies heavily on initial planning accuracy, making early mistakes costly
- Can give a false sense of security if slack time is misinterpreted
How ProjectManager Facilitates Critical Path Analysis
ProjectManager facilitates critical path analysis by providing robust resource management tools that ensure the right people are assigned to the right tasks at the right time. The availability feature lets managers see who is free to take on work, helping avoid overloading team members on critical tasks.
The color-coded workload chart offers a clear visual of team capacity, making it easier to rebalance assignments if someone is overallocated. The team page centralizes all this information in one place, giving project managers a real-time view of their workforce so they can keep the critical path moving without delays caused by resource bottlenecks.
Use The Right Tool for the Task
Multiple project views also support critical path analysis by offering flexible ways to visualize and manage tasks. The Gantt view is ideal for identifying and filtering the critical path, linking dependencies and setting start and end dates. The kanban board helps teams manage task flow and spot blockers that could impact the schedule.
The list view gives a straightforward way to track task status and ownership, while the calendar view allows teams to manage deadlines and milestones in a time-based layout. The sheet view resembles a spreadsheet and is perfect for bulk task editing and organizing complex project data. Together, these views provide a full-picture understanding of how tasks interact and affect the critical path.
Keep Track of Progress in Real Time
Tracking progress in real time is essential for effective critical path analysis, and our software excels with its integrated monitoring tools. The real-time project and portfolio dashboards show task progress, team workload and deadlines at a glance, making it easier to spot delays on the critical path.
Customizable reports allow managers to focus on key metrics and generate tailored insights for stakeholders. Secure timesheets track actual hours spent on each task, giving accurate data to compare against the baseline. With this level of visibility and control, ProjectManager ensures your critical path stays aligned with project goals and timelines.
Related Critical Path Analysis Content
Critical path analysis is an important part of project planning. For those who want to learn more about it, the following links lead to stories on critical path software, how to display the critical path in a Gantt chart and much more.
- Critical Path Software
- Critical Path Method (CPM) in Project Management
- Displaying the Critical Path on a Gantt Chart
- Critical Path Method (CPM) in Construction: A Quick Guide
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