What Is a PERT Chart?A PERT chart is a network diagram that allows project managers to create project schedules. They’re used in the Program Evaluation Review Technique (PERT) to represent a project timeline, estimate the duration of tasks, identify task dependencies and find the critical path of a project.
PERT charts are used by project managers to create realistic schedules by coordinating tasks and estimating their duration by assigning three time estimates for each; optimistic, most likely and pessimistic. This makes PERT charts useful when planning projects where the duration of activities is uncertain.
Related: 12 Free Project Scheduling Templates for Excel
PERT charts are more powerful when combined with online project management software such as ProjectManager. ProjectManager has Gantt charts, kanban boards and task lists so you can plan, schedule and track your projects. Make dynamic project schedules that update in real time as your team completes their tasks. Get started for free.
When Should I Use a PERT Chart?
Use PERT charts during the planning phase of a project. They can help you determine the project’s critical path and the ideal time to start or finish tasks, which allows you to know which tasks need to be prioritized when creating your project schedule.
As noted, PERT charts show the dependent tasks in your project. These are tasks that can’t start or finish until another task starts or finishes. Knowing which tasks are dependent helps you prevent delays by planning ahead to make sure these dependent tasks are scheduled in the order they need to be completed.
Also, when planning a project, having an accurate forecast of its duration is crucial for resource scheduling. The PERT chart is a tool that can help you estimate the amount of time you’ll need to complete the project. It’s also very helpful when you’re working on more complex or larger projects.
How Does a PERT Chart Work?
A PERT chart is made up of nodes and directional arrows. Nodes are numbered boxes or circles. They represent an event or milestone in the project. The arrows are the tasks or activities that must be done before moving on to the next event or milestone.
Therefore, a PERT chart works by visualizing the project’s tasks and dependencies. This provides an overview of the project timeline, including which tasks are essential to complete to deliver a successful project. With this information, project managers can develop a viable project plan that meets deadlines and stays within budget.
Related: Free Gantt Chart Template for Excel
How to Make a PERT Chart in 4 Steps
Creating a PERT chart shouldn’t be an overwhelming process, even if you decide to draw your PERT diagram and do the calculations yourself. Here are some simple steps to create a PERT chart:
1. Break Down Your Project Scope
Begin by identifying the project milestones and then identify the individual tasks required to achieve them. Then, figure out the sequence of your project tasks and their dependencies.
You should have a list of milestones, tasks and their dependencies. You’ll need these elements to create your PERT chart, either manually or using project management software.
2. Create Your PERT Chart
Now that you have the information that you need, you can now make the PERT diagram—we’ll show you a PERT chart example in the section below!
During this phase, you’ll need to sequence your tasks using the PERT diagram and estimate the time required to complete each task.
3. Estimate Your Project Duration
Now that you have drafted a PERT diagram and added task details, it’s time to add the estimated durations of all tasks to create a project schedule. If you’re drawing your PERT diagram, you’ll use the PERT chart formula to do so.
If you use ProjectManager’s Gantt chart, you’ll automatically create an interactive project schedule that lets you identify task dependencies, set due dates, estimate your project duration, find the critical path and much more.
4. Find the Critical Path & Slack
Once you have a PERT chart that has your project tasks, their durations and due dates, you can calculate the critical path and identify any possible slack. At last, you have your PERT chart! Remember, this project management chart is a living document that must be returned to and revised as the project progresses.
PERT Chart Example
Let’s move these concepts from abstraction to reality. To better understand the power of a PERT chart in
project management, let’s make one together. For our PERT chart example, we’ll create a project around building a website. The PERT chart will allow us to visualize our project’s activities and milestones to quickly uncover the critical path.
To begin our PERT example, we’re going to identify all the activities that make up the project and determine the immediate predecessors for each. We’ll list them as shown in the table below.
Next, we figure out how long all the activities will take. The amount of time you estimate with the PERT chart formula should be added to the arrows as shown in our PERT chart example. We used weeks as our time unit, but it could be days or months, depending on your project.
Once we have a time estimate for each task, we can draw our PERT diagram. We start with the first node which is the “kick-off meeting” in our example. Then we represent the initial activities with arrows and connect them to their corresponding milestone nodes. We continue the process until we get to the final milestone node of our project.
Pro tip: A PERT chart is a great way to help you estimate simply and more accurately. Estimates can be overly optimistic or pessimistic, but using a PERT chart will find the most realistic estimate.
Advantages of Using PERT Charts for Project Management
Simplify Complex Projects
PERT charts help project managers get a handle on complex projects. They’re useful because they provide an estimation of how much time you’ll need to schedule the project and what resources will be required. The nature of the PERT and its breakdown structure helps to visualize the complexity of a project and the dependencies between each step in the process.
Involve Multiple Departments & Subject Matter Experts
A PERT chart also serves as a project management tool that pulls in data from every department working on the project. This helps project managers identify who is doing what and provides clear responsibilities for those tasks. Strong communication is facilitated between departments, and the overall strategic goals of the organization are better aligned.
Explore the Hypothetical
Another benefit of using a PERT chart is it allows project managers to create what-if scenarios. By mapping out the tasks, time and resources for a project, you can quickly see what’s working and what’s not. This saves a lot of time that would otherwise be wasted on revisions. This flexibility makes PERT charts useful in project management.
Disadvantages of Using PERT Charts for Project Management
PERT charts aren’t a quick fix to get your projects magically on track, though. Naturally, bad data in results in bad data out. It’s important that the person conducting the PERT analysis has experience in the process.
They’re also labor intensive, which some organizations might not have the time or money to invest in. Additionally, you don’t build a PERT and call it a day. They require continuous reviews and updates to make sure they’re accurate. If you’re using a PERT chart template, you’ll have to create many versions of it.
PERT Chart vs. Gantt Chart
While both PERT charts and Gantt charts are visual tools used by project managers for project planning, they’re not exactly the same thing.
PERT charts, as detailed above, were developed to simplify planning and scheduling larger and more complex projects. Gantt charts, on the other hand, are also a graphical depiction for planning and scheduling a project, which breaks down the project scope into tasks that populate a timeline. A Gantt chart can be used to build the project timeline, set task dependencies and show the duration of each task.
There are other key differences as well. For example, Gantt charts represent the project timeline with a bar chart. A PERT chart is more of a flowchart or network diagram. Gantt charts can be used on smaller projects, while PERT charts are for larger and more complex projects.
The most salient difference is that a PERT chart is usually used before starting a project to figure out scheduling, while Gantt charts tend to follow into the project, highlighting scheduling constraints. Gantt chart software can be used by project managers when executing the project as well as when planning because tasks’ start and end dates can be edited. Gantt charts reveal how long each task will take, show who on the team is responsible for those tasks and are a more transparent tool to track progress and keep track of tasks and resources.
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