What is the Critical Path Method?

The critical path method (CPM) is a project modeling technique that’s used by project managers to find the important deadlines and deliver a project on time. In a project, the critical path is the longest distance between the start and the finish, including all the tasks and their duration. Once a critical path is determined, you’ll have a clear picture of the project’s actual schedule.

To find this, project managers use the CPM algorithm to find the least amount of time necessary to complete each task with the least amount of slack.

Once done by hand, nowadays, the critical path is calculated automatically by project scheduling software. That makes the whole method a whole lot easier.

A screenshot of ProjectManager.com’s gantt chart, showing a critical path filter. A button superimposed on top says 'Click here to start your free trial'

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 date. This is simply the earliest date that a task can be started in your project. You cannot determine this without first knowing if any tasks are dependent on this one task, or figuring out other constraints that might impact the start of this task. Next is the earliest finish date. This being the earliest date your task can be completed.

Latest start date. 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 date is for the same reason. By having a clear picture of this timeframe, you can better schedule the project to meet its deadline.

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. When you are collecting tasks for the critical path, they must have zero float. But if the tasks do have some float, then they go on the non-critical path, which means if this task is delayed the project can still finish on 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 Analysis

As mentioned, the purpose of a critical path is to find the least amount of time you’ll need to complete a task. Critical path analysis furthers your ability to make better estimates for scheduling, because you’re mapping out every important task that must be done for a successful project.

Critical Path Example

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.

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.

How to Calculate the Project Critical Path

The technique for figuring out the critical path in your project can be boiled down to five essential steps.

  1. Break Down the Project: List all the tasks needed to complete the project. You can use a work breakdown structure, which is a hierarchical decomposition of the project, which includes every deliverable.
  2. Estimate Task Duration: Now comes the tricky part, you want to know how long each task will take. If possible, get advice from others who have, so you can have the most accurate estimation of the duration of the various tasks possible.
  3. Determine Task Dependencies: If there are any task dependencies, you want to note them, too. A task dependency is when one task cannot start until another one has been finished. It’s a key element of good task management.
  4. Add Milestones: What are the milestones in your project? Having milestones helps to keep you on track, so you can make sure you’re meeting your baseline schedule.

When you have this data collected, you’re able to calculate the longest path your planned tasks will take to reach the end of the project, as well as the earliest and latest that each task can start and finish without impacting the project schedule.

Again, all this determines 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.

Related: Free Issue Tracking Template

There can be more than one critical path. Also, the critical path can change depending on your resource scheduling. It can also change over the course of your project.

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 variance, 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.

Critical Path in Project Management

The critical path 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 task.

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.

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. Critical path 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 to 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.

The Benefits of Critical Path, Summarized

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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