What Is the Critical Path?

In project management, the critical path is the longest sequence of tasks that must be completed to successfully conclude a project, from start to finish. The tasks on the critical path are known as critical activities because if they’re delayed, the whole project will be delayed. By identifying the critical path, you can determine the total duration of a project, and you’ll have a clear picture of the project’s actual schedule.

To find the critical path, project managers use the critical path method (CPM) algorithm to define the least amount of time necessary to complete each task with the least amount of slack.

Once done by hand, nowadays the critical path can be calculated automatically with project scheduling software, which makes the whole method much easier.

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What is the Critical Path Method in Project Management?

The critical path method (CPM), also known as critical path analysis (CPA), is a scheduling procedure that uses a network diagram to depict a project and the sequences of tasks required to complete it, which are known as paths. Once the paths are defined, the duration of each path is calculated by an algorithm to identify the critical path, which determines the total duration of the project.

The critical path method (CPM) is used in project management to create project schedules and helps project managers create a timeline on a Gantt chart for the project. The critical path method includes:

  • Identifying every task necessary to complete the project and the dependencies between them
  • Estimating the duration of the project tasks
  • Calculating the critical path based on the tasks’ duration and dependencies to identify the critical activities
  • Focusing on planning, scheduling and controlling critical activities
  • Setting project milestones and deliverables
  • Setting stakeholder expectations related to deadlines

After making these considerations, you gain insight into which activities must be prioritized. Then, you can allocate the necessary resources to get these important tasks done. Tasks you discover that aren’t on the critical path are of a lesser priority in your project plan, and can be delayed if they’re causing the project team to become overallocated.

Gain Insight When Planning Tasks

Projects are made up of tasks that have to adhere to a schedule in order to meet a deadline. It sounds simple, but without mapping the work it can quickly get out of hand and you’ll find your project off track.

When you’re analyzing the critical path, you’re looking closely at the time it will take to complete each task, taking into account the task dependencies and how they’ll impact your schedule. It’s a technique to find the most realistic project deadline. It can also help during the project as a metric to track your progress.

Therefore, when you’re doing critical path analysis, you’re finding the sequence of tasks that are both important and dependent on a previous task. Less important tasks aren’t ignored and are part of the analysis; however, they’re the ones you know can be jettisoned if time and money won’t permit.

Need help deciding which tasks to prioritize? Project management software makes it easy to analyze your project tasks because it provides a central location where you can input critical project data in a digestible manner. ProjectManager.com, for instance, lets you attach crucial details to tasks like planned duration, expected cost, workload allocation, dependencies and more. Once all this information is in one place, you can quickly sort through your tasks and identify those that are most essential.

team collaboration on Gantt

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Critical Path – Definition of Terms

To properly understand the concept of critical path, you first need to understand the various terms used in this method.

Earliest start time (ES): This is simply the earliest time that a task can be started in your project. You cannot determine this without first knowing if there are any preceding tasks, or figuring out other constraints that might impact the start of this task.

Latest start time (LS): This is the very last minute in which you can start a task before it threatens to upset your project schedule. And you need to calculate what the latest finish time is for the same reason. By having a clear picture of this timeframe, you can better schedule the project to meet its deadline.

Earliest finish time (EF): The earliest an activity can be completed, based on its duration and its earliest start time.

Latest finish time (LF): The latest an activity can be completed, based on its duration and its latest start time.

Float. Also known as slack, float is a term that describes how long you can delay a task before it impacts the planned schedule and threatens the project’s deadline. The tasks on the critical path have zero float. You can either calculate the float using the steps above, or by using project management software. If an activity has a float greater than zero, it means it can be delayed without affecting the project completion time.

Crash duration. This describes the shortest amount of time that a task can be scheduled. You can get there by moving around resources, adding more towards the end of the task, to decrease the time needed to complete the task. This often means a reduction in quality, but is based on a relationship between cost and time.

Critical path drag. If time is added to the project because of a constraint, that is called a critical path drag, which is how much longer a project will take because of constraints on tasks in the critical path.

How to Calculate the Critical Path

Now that you know the key definitions of CPM, here are the steps to calculate the critical path in project management:

  1. Collect Activities: Use a work breakdown structure to collect all the project activities that lead to the final deliverable.
  2. Identify Dependencies: Figure out which tasks are dependent on other tasks before they can begin.
  3. Create a Network Diagram: A critical path analysis chart, or network diagram, depicts the order of activities.
  4. Estimate Timeline: Determine the duration of each activity.
  5. Use the Critical Path Algorithm: The algorithm has two parts; a forward pass and a backwards pass.
  6. Forward Pass: Use the network diagram and the duration of each activity to determine their earliest start (ES) and earliest finish (EF). The ES of an activity is equal to the EF of its predecessor, and its EF is determined by the formula EF = ES + t (t is the activity duration). The EF of the last activity identifies the expected time required to complete the entire project.
  7. Backward Pass: Begins by assigning the last activity’s earliest finish as its latest finish. Then the formula to find the LS is LS = LF – t (t is the activity duration). For the previous activities, the LF is the smallest of the start times for the activity that immediately follows.
  8. Identify the Float of Each Activity: The float is the length of time an activity can be delayed without increasing the total project completion time. Since the critical path has no float, the float formula reveals the critical path: Float = LS – ES
  9. Identify the Critical Path: The activities with 0 float make up the critical path.
  10. Revise During Execution: Continue to update the critical path network diagram as you go through the execution phase.

These steps determine what tasks are critical and which can float, meaning they can be delayed without negatively impacting the project by making it longer. Now you have the information you need to plan the schedule more accurately and have more of a guarantee you’ll meet your project deadline.

You also need to consider other constraints that might change the project schedule. The more you can account for these issues, the more accurate your critical path method will be. If time is added to the project because of these constraints, that is called a critical path drag, which is how much longer a project will take because of the task and constraint.

What Is Critical Path Software?

Critical path software is used to automatically calculate the critical path in your project schedule. Without using software, managers would have to manually calculate the time-consuming and complicated equation.

Time is one of the triple constraints of a project, so it’s understandable why critical path software has become popular in project management. Any opportunity to gain efficiencies steers the project closer to meeting its goals and objectives.

Since critical path is a very specific technique, critical path software is usually associated with a larger project planning tool that organizes tasks, prioritizes the sequence of activities and other features that go into creating the schedule. One of the most commonly used project management software to identify the critical path is Microsoft Project. However, it has major drawbacks that make ProjectManager.com a better choice.

Benefits of Critical Path Software

Knowing the critical path and having a tool to recalculate it as your schedule evolves over the course of the project is key to getting back on track when you’re behind schedule. More benefits to using critical path software include the following.

  • Quick Calculations Save Time and Effort
  • Track Progress To Know If You’re Behind
  • Recalculate As Project Schedule Changes
  • Keep Track of Task Dependencies
  • Set Milestones and Save Important Dates
  • Get Insightful Data When Planning Tasks
  • Create Schedule Baseline for Project Variance

Must-Have Features of Critical Path Software

Link Tasks and Avoid Bottlenecks

Tasks that are dependent on another need to be a part of your critical path calculation. There are four types: those that are start-start, start-stop, stop-start and stop-stop. By identifying these task dependencies, you can avoid bottlenecks later on in the project.

A screenshot of ProjectManager.com’s gantt chart, with lines between the bars that represent task dependencies

Get High-Level View of Your Progress

Dashboards are an essential feature for staying on schedule. They provide a window into the project’s performance and progress by collecting data and displaying it in graphs and charts that show various metrics, such as costs, tasks and more.

A screenshot of a dashboard in ProjectManager.com

Make More Insightful Decisions

Keeping track of a project as it’s executed is how you stay on track. But if the information you’re gathering is dated, then you’re always going to be playing catch up. With real-time data from a cloud-based critical path software tool, you’re always seeing the project as it currently is.

A screenshot of the gantt chart with columns that show project progress, including cost

Know Your Project Variance

Schedules are always changing as the project is impacted from internal and external forces. To make sure you’re on target, you need to have a feature that is collecting data and displaying project variance, so you can compare the actual progress against where you’ve planned to be.

A screenshot of ProjectManager.com’s variance report

Keep a Record of Your Plan

The critical path helps you plan the project, but once you’ve finalized the schedule, you need to set a baseline. This saves the schedule so you can compare it to your actual progress and know if you’re on time, behind or ahead. Any critical path software should have this feature.

A screenshot of the planned end dates column in ProjectManager.com’s gantt chart

See Deep Data on Performance

Reports serve two purposes. They take you deeper into the project and expose insightful data on project variance, timesheets and more, which helps you stay on track. Filtering the results and sharing the reports is a great communication tool for stakeholder presentations.

A screenshot of a report generated by ProjectManager.com

ProjectManager.com and Critical Path

Figuring out the critical path by hand takes time, and it must be done throughout the project, which is why using software streamlines the process. ProjectManager.com is an award-winning software that does all the work for you.

Our online Gantt chart filters for critical path, links dependencies and is integrated into a full project management software. Sign up for a free 30-day trial of our software and follow along to build a dynamic Gantt chart and automatically calculate your critical path in a few easy steps.

1. Start a Project with a Gantt Chart

Managing a project on Gantt charts allows you to both plan and schedule in one place. Add your tasks and their durations, and they will automatically appear on a project timeline, allowing you to see your whole project at once.

In the software, upload your tasks manually, or upload a pre-existing spreadsheet. Add task descriptions, deadlines, priority, tabs and assign to one or more team members. We also provide templates to help you get started.

A screenshot of the Gantt Chart view, with a pop-up to create a new task.

2. Add Dependencies

Linking dependent tasks helps you avoid bottlenecks later in the project, when one task can’t start or finish until another has been completed.

In the software, connect your dependent tasks on the Gantt chart by dragging one onto the other. You’ll see a dotted-line indicating that the tasks are linked, and you can then define the type of dependency it is.

A screenshot of the Gantt Chart view, showing lines that connect bars on the chart that indicate dependency.

3. Set the Project Baseline

Setting the baseline is possible when you have finished making your project schedule, complete with deadlines and cost. The baseline captures your data and uses it to compare against your actual progress.

On the Gantt, create your baseline for the project by adding the start date to the task and when it’s due to be completed. These planned start and end dates will be compared to your actual project data and show you whether you’re on target or not.

A screenshot of the Gantt Chart view, showing Project Baselines that compare planned vs actual progress.

4. See the Critical Path

Now’s the time where you calculate your critical path. You could subtract start and end dates and do all that manually—or you could get a tool that does it for you!

Easily find the critical path of your project by using our critical path filter. This helps you know what must be done to complete the project, and shows if you’re experiencing any slippage.

A screenshot of the Gantt Chart view, with a pop up with filters, including the one to filter by critical path.

5. Get Your Overview with a Dashboard

Now that you’ve got your project planned out, viewing it from a dashboard is the best way to get a high-level view of your progress. Dashboards often must be manually created, but ours automatically crunches the numbers for you and displays them, so you know where you are at a glance.

From the Dashboard view, track if your project is proceeding as planned. Our dashboard monitors several project metrics, such as variance, tasks and more, automatically calculating your data to display it in easy-to-read charts and graphs.

A screenshot of the real-time dashboard in ProjectManager.com, showing various key metrics on graphs.

6. Report on Progress

Reporting is crucial to pull data from your project and get and share insights into how it’s doing. Reports come in many varieties, which together provide a snapshot of the whole project’s performance.

Easily generate reports on critical path, task progress, project status, costs and more in the software. We do the calculations for you, and you can filter the results to show just what you want to see. Our reporting feature is done automatically with one click.

A screenshot of the report generated by ProjectManager.com, displaying project health.

What Is the Difference Between PERT and CPM?

The Critical Path Method (CPM) and the Program Evaluation Review Technique (PERT) are both visual representations of a project schedule, but it’s important to know the differences.

The main difference between PERT and CPM is that PERT was designed to plan projects with uncertain activity times. This is why PERT uses three time estimates for each task: optimistic, most likely and pessimistic. On the other hand, CPM was designed for projects where activity times are certain.

CPM uses a single time estimate for each task and focuses on the analysis of task sequences to estimate the total duration of a project. Another important difference is that the CPM is used to identify critical activities that must be completed on time to avoid affecting the project’s deadline, which is something that PERT can’t do.

PERT can be used alongside the critical path to help estimate the duration of activities.

Critical Path in Project Management

The Critical Path Method is one of the many tools that project managers use when creating their project plan and schedule. It informs them on the length of time, the amount of resources and costs associated with each task and the overall project. Once they have this mapped out they can start plotting the timeline in their scheduling software and start the process of managing their project.

How is Critical Path Useful?

Critical path plays an important role in developing a schedule in project management. It is used in conjunction with PERT (program evaluation and review technique) to figure out the longest amount of time that it would take to complete a project by looking at the dependencies and duration of each task involved.

Simply put, using the critical path is a way to order the seeming chaotic complexity of any project. If deadlines are important to getting a project to deliver on time, then the duration of each task must be understood in order to better estimate where those deadlines will land on the project timeline.

Great for Complex Projects

Again, critical path analysis is charting the dependent tasks, which are those that cannot start or finish until another has started or finished. This creates a great deal of complexity, but the analysis is crucial in order to have a realistic schedule. If your project isn’t as complicated, however, it might not require critical path analysis.

But those who are involved in highly complex projects need to know the amount of float or slack time they have for each task while still meeting their deadline. The value in this is obvious, especially if you’re dealing with a task that’s giving you a hard time. You know when you must resolve the problem or move on.

Why Critical Path Is Important

To summarize, the critical path is important when managing a project because it identifies all the tasks needed to complete the project—then determines the tasks that must be done on time, those that can be delayed if needed (due to the triple constraint of time, cost and scope) and how much float you have.

Armed with this knowledge, you can prioritize, set realistic deadlines and assign the critical tasks to your most capable team members.

How Critical Path Helps Scheduling

The reason for understanding the critical path in project management is that the more accurate and reliable your data, the better your project timeline, schedule, plan and so forth. The critical path of a project shows you not only how long tasks are likely to take, but prioritizes them.

If you’re in the midst of a project and find you’re running behind schedule, you’ll know from your critical path the tasks that must be completed and those that can be left undone without negatively impacting your deliverable. This could mean the difference between a successful project, and a failed one.

Quickly Know Your Progress on a Project

Critical path is also helpful in your project as a measurement of schedule variance. That is, it can help you see where you are in the project compared to where you had planned to be at that time. This information will quickly tell you if you’re on target or lagging behind, and you can then act accordingly.

Another benefit of using the critical path in project management is that it helps identify and map task dependencies. Not all tasks can be done at the same time. There is an order and often that structure means that some tasks can’t start or stop until another has started or stopped. It can help avoid bottlenecks by map parallel tasks and keep the project moving.

Critical Path Example

Here’s an example of a critical path network diagram. Although it’s high-level, it can help you visualize the meaning of a critical path for a project schedule.

Critical path method network diagram

Critical Path Method Benefits

Finding the critical path is a useful tool that project managers use to make better time estimates. It lends itself to complex and larger projects, but it can be a helpful tool no matter the size of your project.

Time is always weighing heavy on a project, and a critical path allows you to see which of the project tasks are not absolutely necessary to end with a quality deliverable. You want to complete every task, but sometimes that’s not possible. Critical path helps you determine which you don’t need.

Once you have your critical path, you want to keep returning to the analysis and continuing to crunch those numbers as things change when executing your project. That’s a lot of work, but when used in conjunction with a robust project management software, you’ve taken the first steps towards success.

If you’re looking to calculate the critical path in your project, then you’re going to need to measure a lot of variables. You’ll need a project management software that can handle those complicated metrics. ProjectManager.com is a cloud-based tool that gets real-time data to determine how accurate your planned schedule is to the actual one, so you can adjust immediately if necessary. See how it can help your project by taking this free 30-day trial.

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