At first, understanding how to calculate critical path, and how to use the critical path method in project management can seem daunting. But when you move past the concept of using a lot of data and algorithms to calculate it, you realize it’s pretty common sense! Show
In this article, we’ll take a dip into the critical path concept and its components, talk about why it’s a useful tool, and give you some critical path method examples, solutions for using project management software, and tools to aid you in calculating critical path. What Is Critical PathIn short, the definition of critical path is as follows:
Most projects are broken down into tasks, or activities (whatever you want to call the smaller bits that need to be completed in order to get the project done). The critical path is the series of those tasks that, when followed in sequential order and accounting for all the above variables, will take the longest to complete the project.
Importance of the Critical Path MethodThe beginnings of using sophisticated project management systems such as the critical path method can be traced back to monumental projects such as the building of the Great Pyramid of Giza, the Great Wall of China, the Panama Canal, and the Trans-Siberia Railroad, just to name a few. Imagine what these history-altering construction projects would look like if it weren’t for project management systems like the critical path method. Chaos, right? The same is true for current projects in today’s organizations. Without the ability to calculate potential obstacles within the timeline of a project, analyze the components of the project required for completion, and develop solutions resolving those obstacles, many projects would never leave the ground.
Note the word “successfully” there because the worst-case scenario is, the project will be late and fail to achieve its goal(s). While the critical path method may not be the only project management method out there, it’s the go-to methodology for many project managers.
See this post for a comparison of this and other popular project management methodologies! How to Calculate Critical PathBefore we dive in, for the visual learners among you, here’s a great, highly detailed video showing how to calculate the critical path: Finding the critical path for a project rests first on six steps completed in order. Let’s break down those steps! STEP 1. Divide the Project into Tasks
STEP 2. Order and Identify Dependencies
STEP 3. Create the Network DiagramNow, you can make your task line-up visual. The good old pen-and-paper method may work well; a more sophisticated way of doing this is by using a network diagram such as a PERT or Gantt chart (more information to come on these later in this article) and connecting your tasks in the chart. STEP 4. Estimate Duration
STEP 5. Perform Resource LevelingThe main aim of resource leveling is to allocate resources efficiently so that the completion of a project lies within the given time, and no resource conflicts take place. Resource conflicts may lead to:
STEP 6. Determine the Critical PathFind the longest sequence of project tasks in the diagram. This sequence is the critical path for your project! Image credit: ResearchgateEDITOR’S NOTE 1: There are usually three main types of anticipated dependencies in a project.
EDITOR’S NOTE 2:
Variables Within Critical PathLet’s take a look at some terms and concepts you’ll need to understand to be able to calculate the critical path. Float/SlackFloat (sometimes called slack) of a task is the duration that it can be delayed without delaying the subsequent task, completing the project, or violating a schedule constraint. Early Start and Early FinishEarly start and early finish are just that: the most initial time a task on a path can begin, and the earliest it can finish. Beginning a task on its early start is conditional upon the completion of tasks on the same path. If the prior task can finish on its early finish time and it completes the last task on the path, the team can begin with an early start on the next task, freeing up more time to use on other, more unpredictable tasks. 👉 Forward Pass Method of Determining Early Start: Beginning with a project start date, you can assess an early starting date for each subsequent task on the project path by following it from left to right in the diagram. 👉 Steps to calculating Early Start dates:
Late Start and Late FinishLate start and late finish are adverse. They’re the latest beginning, and ending dates a task can be assigned without derailing the other tasks on the path or the whole project altogether. Begin with the project plan’s completion date, then the critical path, then paths of descending order of completion dates. Work right to the left through the network diagram and subtract the time each task will take on each path to calculate the latest date that task could begin while still meeting the project’s completion date. Just as with the forward pass (early start/finish, left to right), resources must be taken into account when expediting the backward pass. Steps to calculating Late Starts dates
To calculate late start dates, begin with the project completion milestone and assign it as the finish date of its predecessor activities. Follow the steps above to estimate the late start dates of predecessor activities, assuming finish-start relationships. Tools and Software to Calculate Critical PathBelow, we’ll take a glance at some CP software, templates, and diagram generators available on the web to help get you started, stay organized, and be successful when determining the critical path for your project. We’ll also get into how to use a PERT or Gantt chart to estimate critical path, and provide a clear, visualized model for the CP of your project. With a quick google search, you’ll discover there are a host of tools out there to calculate CP, as well as some critical path templates to illustrate your project’s critical path. Capterra provides feature comparisons and ratings between the most popular project management software programs available right now. Many, if not all of them, feature customizable templates and Gantt chart generators to make finding the critical path for your project easier. MS Project has a pretty comprehensive suite of resources for the critical path process, from calculators to Gantt chart generators, to in-house tutorials. You can learn more about finding the critical path in MS Project here. PERT chart for estimating critical pathA PERT chart is an activity-on-arrow visual outline of a project’s schedule. It shows the sequence of tasks on a path and determines the time it will take to complete each, and which of those may be completed simultaneously. Like the critical path method, a PERT chart will contain information like float between activities, early start/finish dates, and late start/finish dates. Usually, PERT comes into play at step four of the critical path method process- determining task completion times. Many project managers use PERT because it estimates completion times based on the most likely scenario rather than unrealistic time frames. When using PERT, you will estimate the shortest, longest, and most likely length of time a task may take if it’s predicted to take longer than anticipated. Terms you’ll need to know to use a PERT chart include:
Here’s a helpful video on how to create a PERT chart: Gantt chart for estimating critical pathGantt charts are best for smaller projects, linking dependent tasks instead of establishing a network diagram showing interconnecting independent tasks as a PERT chart does for larger, more complex projects. While PERT charts usually come into the picture during the planning of a project to determine the most efficient scheduling, the Gantt chart model is generally used as a project is progressing. It illustrates the length of the duration of a task, who is involved and responsible for the task, and reveals scheduling conflicts. In a Gantt chart, you can revise and edit your project’s begin and end dates throughout the project. To create a Gantt chart or bar chart, check out this video: What’s the difference between a PERT and Gantt chart view?Gantt and PERT charts are both visual depictions of a project’s completion, illustrating its tasks, the timeline for those tasks, and variants that can impact the schedule, such as resource leverage and dependencies. The primary difference between a PERT chart and a Gantt chart is its timeline representation. PERT uses a network diagram, or flow chart, while a Gantt chart uses a bar chart as a representation of a timeline. Critical Path Method: In ClosingDue to its incredible effectiveness, the critical path is a project staple in organizations everywhere. We hope this article has helped make learning how to find critical paths much more straightforward. Happy planning! Featured image credit: twproject |