What is a PERT chart?

PERT stands for Program Evaluation Review Technique. A thoughtfully created PERT chart offers you a visual representation of your project and a way to keep track of exactly where you are in the project’s timeline. By outlining each stage from beginning to end and breaking down all the tasks in between, you can gain a more accurate assessment of how long the stages will take and form a realistic timeline to completion.

The Program Evaluation Review Technique was first developed in the late 1950s by the US Navy, specifically as a management tool for the Polaris submarine missile program. The PERT chart is also a close cousin of the Gantt chart, originally developed by Henry L. Gantt in collaboration with his colleague Frederick Taylor, the father of scientific management. PERT revived Taylor’s legendary theories of scientific management, which were later refined by Henry Ford to improve the efficiency of his car-production line.

Outside of the US military, one of the first times the technique was applied on a large scale was from 1965 to 1968 when it was used to plan the Winter Olympics in Grenoble.

What does a PERT chart look like?

PERT charts are structured using a flow chart system and can be drawn as a freeform diagram (as opposed to similar project-management charts like the Gantt chart, which is highly structured). Project managers create numbered boxes or circles known as nodes. Each node corresponds to an event, set of tasks or milestone in the project. Nodes can be linked by two types of arrows: directional (or concurrent) arrows and divergent arrows.

1. Directional arrows

These represent the tasks or actions that need to be completed before moving on to the next phase in the project. The tasks or actions have dependencies and must be completed in the indicated sequence.

2. Divergent arrows

These represent tasks that do not have dependencies. The team can therefore work on them simultaneously or in any sequence they choose.

What are the advantages of using a PERT chart?

Using a PERT chart for your project planning offers many benefits. Let’s take a look at some of them.

• Allows project managers to determine with greater accuracy how long a project will take and provides a detailed time frame for each task. Team members will be able to ascertain at a glance how the tasks are organised and the order in which they need to be actioned.
• Brings greater clarity to the project and makes it easier to identify dependencies between tasks and what resources are required. This in turn helps project managers make decisions on where best to allocate the available time and resources.
• Lets you plot a critical path. This is the name for the series of tasks with dependencies that takes the most time to finish. Determining the critical path is the fastest way to work out the project’s timeline.
• Enables teams to plan ahead for unforeseen eventualities or delays and improves efficiency. The PERT chart makes it easy to identify bottlenecks and any potential constraints. Spotting these ahead of time decreases the likelihood of problems occurring and can help teams formulate potential solutions in advance in case they do.
• Improves coordination and communication between teams. A PERT chart visually shows the interface between different departments and the role of each person or team involved in the project. This allows team members to see how their various roles interact and contribute to the larger plan.
• In addition to improved communication, working together using a PERT chart can ensure all team members are engaged and enthusiastic and help foster better workplace relations.
• Makes tracking easy. Managers can track assets while the project and its various tasks are being executed and ascertain the overall progress of the project. When assigning tasks to team members, they’ll have a better idea off what kind of deadline is realistic.

Related: The 5 Stages of Team Development

Are there any disadvantages to using a PERT chart?

Depending on your project, a PERT chart might not be the best project management tool, and you may need to consider alternatives. Here are a few potential disadvantages to keep in mind.

• Its subjectivity can make it unreliable. PERT charts are often drawn up with input from many team members. Time and cost estimates can therefore reflect biases team members have or incorrect information they’ve been given. If historical information is used to make any decisions, there’s a chance it may no longer be accurate or relevant in the present day.
• They are over-focused on time. Establishing realistic timelines is the main feature and drawcard of a PERT chart, but it can mean that less attention is paid to other factors like budgeting, financing and resource distribution. If these factors are going to be significant in your project, you may want to consider a different project-management technique.
• PERT charts are complicated and time consuming to make. For smaller or more simple endeavours, the project manager may decide it’s not worth the effort to draw up a PERT chart.

Steps to creating your chart

There are several established steps to creating a PERT chart for your project. Let’s break down some key ones.

1. Identify the project’s tasks

To begin the first step, your team should discuss the project’s overall objectives and break these down into both long-term and short-term goals. Once you’re all on the same page, you can create a list of all the tasks and activities required to get you from beginning to end. You can expand each action with more details and an estimated time frame and plot milestones to reach.

2. Determine any task dependencies

During this step, you’ll take a closer look at the tasks and activities you’ve laid out and determine whether specific actions need to be addressed in a certain order. Dependencies refer to any task that cannot be completed before another one. Tasks that rely on one or more other tasks are considered as having a logical relationship. Understanding the logical relationships within your project and what actions can or cannot be worked on simultaneously will increase your ability to set an accurate timeline.

3. Create your diagram and connect the tasks

During this step, you’ll draw up your chart. You’ll fill in your nodes and connect them with arrows. You can also use arrows to highlight task dependencies. You can plot your PERT chart by hand or use specialised software. You could also combine these two methods by converting a rough drawing into a digital chart. Using software to create your diagram makes it a lot easier to make changes or create different renditions for the same project to plot hypothetical sequences or outcomes if you’re unsure of any aspects of your approach.

4. Establish timelines and complete the chart

Once you have a chart featuring all tasks and dependencies in front of you, it will become easy to establish your timeline. During this stage, you can use the critical path method we mentioned earlier in this article. By looking at the longest section of the project and calculating the time you think it will take to finish, it will be easier to estimate time frames for other tasks. There are three types of time you’ll work with in project management.

• Optimistic time: the minimum amount of time it will take to complete a task
• Pessimistic time: the maximum amount of time it will take to complete a task
• Most likely time: an estimate somewhere between the optimistic and pessimistic values

The PERT system offers a special formula that comprises these three times. It’s considered to provide a high degree of accuracy. The formula calculates expected time and is laid out as such: expected time = (optimistic + 4 x most likely + pessimistic) / 6

Once your expected time (your timeline) has been determined, you can complete the chart with any final details or make edits.

How to use your new chart

Once you’ve created your chart, you can assign tasks to different members of the team and launch the project. You’ll need to keep working with the chart to track progress and plot any changes or redirections if you run into problems. You can pair this type of maintenance with a change-control process to help you communicate your changes.

Related: Tips to manage change in the workplace

In spite of its origins predating the digital age and the myriad tech tools available to project managers today, the PERT chart still holds its ground in the workplace. Its collaborative nature makes it a popular choice for projects that involve many team members or interdepartmental work, while the clear structure appeals to humans’ visual nature, providing a detailed overview at a glance.