What Is a PERT Diagram

A PERT diagram, sometimes called a PERT chart, is a project management tool used to schedule, organize, map out, and coordinate tasks within a project. It provides a graphical representation of a project's timeline that enables project managers to break down each task in the project for analysis. The name PERT is an acronym for Program Evaluation and Review Technique. A PERT chart is a great way to help you estimate more accurately. 

A shared project-planning workspace gives the team a place to review the task network together before turning estimates into dates.

In this article, you are going to learn everything about the PERT chart. Keep reading.

Pros and Cons of the Pert Diagram

Pros

• It's great for visualizing the project - A PERT diagram can be regarded as an excellent bird's eye view of a project. You can spot any potential bottlenecks and obstacles in the chart. It's easy for all involved parties to identify their roles and execute them on time.
• The PERT chart identifies the critical path very well - The critical path method is the central tenet of the PERT technique. The critical path is the longest-duration route through the dependency network. It determines the earliest possible project finish under the modeled durations and dependencies; it does not guarantee that deadline.
• Allows for individual activity analyses - To do this analysis well, you must study each task. What does each task on the project need? What prior tasks need to be completed before you can move on to the next task? What resources need to be in place? The PERT chart will display these things clearly, so nothing falls through the cracks.
• PERT analysis helps coordinate departments - Gathering qualitative and quantitative data from all involved departments makes the PERT chart collaborative. Departments can see their roles and deadlines.
• You can conduct what-if analysis easily - PERT analysis encourages you to look at all potential scenarios for completing the project. This is because of the emphasis on critical and subcritical paths. It's easy to conduct what-if analysis on any path to project completion.

Cons

• PERT can be too time focussed - PERT places a very heavy emphasis on time. It sets out deadlines for the project tasks to ensure that the project is always on track. Therefore, it could not be a very flexible project management tool. It may only be suited to some projects.
• PERT charts are subjective - The success depends on the project manager's experience. Consequently, some charts may include unreliable data or unrealistic expectations for the cost and time frame of the project.
• Shared resources need separate attention - A dependency network does not by itself resolve conflicts when several tasks or projects need the same person or equipment. Check capacity alongside the network before committing to dates.
• PERT analysis is very labor intensive - It takes a lot of time and thought to create a PERT chart. This is doubly true of complex charts that span a long period with multiple participants. If you need to change something in the chart, it will take a long time to alter all of the subsequent project tasks on the project timeline.
• Not an ideal method for long-term projects - Long-term complex projects can get unwieldy on PERT chart. You need to add new project tasks as the timeline progresses. It also may require more staff members to get involved. This is hard work for the project manager to track the entire project's progress.

What Makes a Pert Diagram

Terminologies of the Pert Diagram

There are numerous terminologies used for PERT diagrams, and we'll mention a few.

• Scope: A specific definition of what the project does and does not entail. A well-researched and coordinated scope of work is critical to managing the expectations of customers and workers alike.
• Task: A task is an arrow-shaped element of a PERT chart representing an activity that must be performed. A predecessor must satisfy a dependency before its successor can proceed. A task can have both predecessors and successors; these describe its relationships, not two exclusive task types.
• Critical Activity: Critical activity is an activity that has slack equal to zero. In a basic, unconstrained finish-to-start network, activities with zero total float lie on a critical path. Date constraints and resource restrictions require additional schedule analysis.
• Critical Path: The longest time path through the task network. The "longest" path (in terms of time) to the completion of a project.
• Crashing: Crashing shortens the schedule by adding resources to suitable critical-path activities, comparing the additional cost with the time saved. Adding people does not shorten every activity.
• Relaxation: The method that is the opposite of crashing a project. Relaxation is used to lower costs while extending the duration of the project. 
• Slack Time: Total float measures how long an activity can be delayed without delaying the modeled project finish; it is a time allowance, not spare resources. The amount of time a task can be delayed before the project finish date is delayed.
• Constraints: Restrictions set on the start or finish date of a task.
• Dummy activity: An imaginary activity with no duration, used to either show an indirect relationship between 2 tasks or clarified the tasks' identities.
• Milestone: A milestone (also known as a PERT event) is an element of a PERT chart, marking the start or completion of a task or several tasks. It consumes no time and uses no resources. 
• Expected Time: Expected time is the best estimate of the time required to accomplish an activity (te) or a path (TE), accounting for the fact that things don't always proceed as normal (something goes wrong, something goes better than expected).
• Fast-tracking: Project activities are initially supposed to be completed sequentially but performed simultaneously to save time. 

Components in a PERT Diagram

Numbered nodes

These are the numbered boxes you see in the PERT chart example above. (Some project managers choose to draw them as circles.)

Each node represents an event or milestone in the project, the completion of one stage, or a series of tasks needed to move the project forward.

Directional (or concurrent) arrows

These arrows on a PERT chart represent the tasks or activities that need to be completed before the team can move on to the next event or phase of the project.

Divergent arrows

These arrows represent tasks a team may work on simultaneously or in any sequence they choose because they do not have dependencies.

Formulas Used for a Pert Diagram

The PERT estimate (E) is based on a formula that includes your optimistic time estimate (O), your most likely time estimate (M), and your pessimistic time estimate (P). The basic equation is this: E = (O + 4M +P) / 6. If you have difficulty with equations, consider using a PERT calculator on the web to simplify things.

At the same time, PERT can help to calculate the standard deviation (SD) from this estimate. The PERT equation for this value is SD = (P-O) / 6. This standard-deviation approximation describes the spread implied by the three estimates; it does not measure the accuracy of the estimate or establish a guaranteed completion window. Project uncertainty also depends on the network and relationships between activities. Web-based calculators are available online to simplify the standard deviation calculation for convenience.

For example, suppose a task has optimistic, most likely and pessimistic estimates of 2, 5 and 8 working days. Its PERT expected duration is (2 + 4 × 5 + 8) / 6 = 5 days; its approximate standard deviation is (8 − 2) / 6 = 1 day. Use the same time unit for all three inputs. These are planning estimates, not measured outcomes.

Now consider two parallel routes: A → B → D takes 2 + 5 + 1 = 8 days, while A → C → D takes 2 + 3 + 1 = 6 days. D waits for both B and C. The first route is critical; C has 2 days of total float in this simplified network. For an activity, total float is LS − ES or LF − EF, where ES/EF are earliest start/finish and LS/LF are latest start/finish. Subtracting ES from LF would incorrectly include the activity’s own duration.

The PMI scheduling standard explains three-point duration estimates and schedule-network analysis.

Create a Pert Chart with Boardmix

You can draw a PERT chart by hand or use PERT chart software to create visualizations. Boardmix is the software that helps you create PERT charts quickly and easily and improve your team's resource distribution.

Boardmix is an industry-leading PERT chart software with many features and benefits, including:

• User-friendly interface that is intuitive and easy to learn.
• Convenient and simple file management.
• Customize shapes, labels and arrows to explain your project’s dependency network.
• Share the PERT chart by board link, or present it during a meeting using screen sharing.
• Built-in templates for different chart styles and various use cases.

Able to collaborate with your workmates in real time and share the file via link.

How to Make a PERT Chart

To simplify the procedure, you can register and log onto the Boardmix first. We have provided a list of actions to assist you in making a PERT chart that you may modify to your project's requirements.

• Identify the major milestones in your project and the steps necessary to attain each one. Create a list of these.
• Set up the order. Choose the steps you must take to fulfill each of these milestones in the correct sequence.
• Establish the necessary timeframe. Namely how long each task should take.
• Create an outline: Outline your PERT diagram using your list. Project milestones should be represented by "nodes" that are presented as circles, triangles, or boxes. 'Vectors,' which are arrows used to connect the series of jobs and emphasize their interdependencies, should be utilized to connect these nodes.
• Calculate the duration of each complete dependency route and identify the longest one. That critical path sets the earliest project finish for the modeled network.
• Revise when circumstances change. You'll likely keep getting new information throughout your project, which will cause your timelines to adjust. So that the team can utilize the PERT chart as a trustworthy tool throughout the project. Therefore, keep updating it frequently to reflect these changes.