Difference Between PERT and Gantt Chart

Introduction

The process of utilizing one's expertise, knowledge, tools, and procedures to finish the activities that make up a project to achieve its objectives or fulfill its requirements is known as project management. The major source of aid for people or project managers to assess, prioritize, and arrange the activities or work required in a full project comes in the form of project management tools. In today's environment, tools for managing projects provide a variety of capabilities, each of which contributes to the timely completion of the project.

In project management, the activities or tasks involved in a project are often represented from beginning to conclusion using either Gantt charts or PERT, which stands for Program Evaluation and Review Technique. They make it possible for us to see the process and the strategy for the project. The primary distinction between PERT charts and Gantt charts is that each makes use of a different set of conventions to convey the information about the project.

Visualization tools such as the PERT chart and the Gantt chart are used often in the management of projects. Both of these charts are used in the process of task scheduling, as well as regulating and managing the activities that are required for the successful completion of a project. The PERT chart is an example of a network diagram, while the Gantt chart is an example of a bar chart. This is the primary distinction between the two.

PERT vs Gantt Chart

The main difference between a PERT chart and a Gantt chart is that the Gantt chart displays, via the use of a bar chart, the precise amount of time necessary for the completion of each activity or task, whereas the PERT chart, which displays information in the form of a flow chart, can only determine the amount of time required for the entirety of a project and not for each task.

That is to say, the Gantt chart offers precise information on the amount of time required for tasks and may be used for very modest projects. PERT charts are useful for big and complicated projects because they can accurately anticipate the total time of the project.

PERT charts are a kind of network diagram that display dependencies between tasks using arrows and boxes to represent the tasks and their respective dependencies. The boxes are organized from left to right, however, the Y-axis does not have any dates permanently attached to it.

The first box, also known as the root, should be positioned such that it is vertically centered on the left side of the diagram. After that, the successive jobs may be created wherever along the Y-axis. Only to the right, to the top, or the bottom, but never to the left, may arrows point.

Gantt charts are bar graphs. Dates are listed along the X-axis, while individual jobs are detailed along the Y-axis. The chart illustrates a bar on each line of the Y-axis, with the bar's location being such that it extends from the beginning date of the job to the finish date of the task. 

Difference Between PERT and Gantt Chart in Tabular Form

Parameter of Comparison	PERT	Gantt
Clarity	The PERT chart will identify the correct information of the whole project split down into activities, but it will not be able to precisely anticipate the time periods for each activity.	When it comes to huge projects, the Gantt chart will be difficult to grasp since it precisely calculates the amount of time needed to do each work, but it does this for every item in the project.
Project Size	The PERT chart will be helpful for projects that are both huge and complicated.	For tasks that are uncomplicated, straightforward, and simple, a Gantt chart will be beneficial.
Interdependency	The PERT chart illustrates networks of tasks that are reliant on one another.	There is no way to represent the interdependency between the jobs using a Gantt chart.
Representation	A flow chart or network diagram may be used to illustrate project information when utilising a PERT chart.	A bar chart is used to represent the specifics of a project in a Gantt chart.
Structure	The tasks or activities being shown on a PERT chart as well as their dependencies are represented by boxes and arrows.	The start date, the finish date, and the duration of the tasks are shown on a Gantt chart by bars, the length and location of which explain the respective values.

What is PERT?

The full name of this methodology is the Program Evaluation and Review Technique, or PERT for short. The PERT chart is widely regarded as one of the most effective tools for use in project management.

A PERT chart is a statistical tool that project managers use to assess and arrange the needed number of activities in a full project, plan the completion of each work, and coordinate each task to ensure the successful completion of the project.

In the year 1958, the United States Navy was the first to develop the PERT chart, and nowadays, it is used in conjunction with the critical path approach. Its original purpose was to simplify the process of planning and scheduling big projects, such as the United States Navy's Polaris submarine nuclear program.

A graphical depiction of a project's chronology may be obtained via the use of a project management tool known as a PERT chart. The Program Evaluation Review Technique, often known as PERT, dissects a project into its parts so that each one may be evaluated separately. PERT charts are often more difficult to comprehend than Gantt charts, although in certain circumstances they are believed to be better than Gantt charts because they indicate task relationships.

The tasks involved in a project may be analyzed with the assistance of a PERT chart, which also provides an estimate of the amount of time needed to accomplish each work in the project. With the help of these details, the manager of the project may formulate an educated guess on the minimal amount of time necessary to finish the project in its entirety. This information is also helpful to the management in developing a budget for the project as well as determining the resources that are required to complete the project.

A PERT chart employs circles or rectangles called nodes to indicate project events or milestones. These nodes are connected via vectors or lines that stand for the different responsibilities. Dependent tasks are those that cannot be completed in any other way than the one specified. On a PERT chart, if an arrow is drawn from Task No. 1 to Task No. 2, for instance, Task No. 1 must be finished before work may begin on Task No. 2.

Parallel tasks are tasks that are being worked on inside a project that is at the same level of production as one another but are on separate task lines. They are not related to one another in any way, yet it is intended for them to take place simultaneously.

What is Gantt Chart?

One of the most frequent and helpful methods of displaying activities (tasks or events) against time is via the use of a Gantt chart, which is often utilized in the management of projects. A list of the activities may be found on the chart's left side, and an appropriate time scale can be found along the chart's top. A bar is used to symbolize each action; the location of the bar and its length indicate the beginning date, length of time, and ending date of the activity, respectively.

Midway through the 1890s, a Polish engineer named Karol Adamiecki came up with the idea for the first Gantt chart. Adamiecki was managing steelworks in southern Poland at the time and had been interested in various management concepts and practices.

Henry Gantt, an American engineer, and project management consultant, created his version of the chart some 15 years after Adamiecki did, and it was this version that became well recognized and famous in western nations. Gantt was the inventor of the Gantt chart. As a result of this, Henry Gantt's name came to be linked with charts of this particular sort.

In the beginning, Gantt charts were painstakingly created by hand. Whenever there was a change to a project, it was essential to either update or redraw the chart, which restricted its utility. Constant change is a characteristic of the majority of projects. Gantt charts, on the other hand, can be quickly developed, updated, and printed in our day and age thanks to the proliferation of computers and software for managing projects.

Gantt charts are now the most used tool for monitoring the schedules of various projects. For this purpose, it is helpful to be able to present extra information about the different activities or stages of the project. For instance, it is helpful to be able to illustrate how the tasks connect, how far each task has gone, what resources are being utilized for each work, and so on.

Main Differences Between PERT and Gantt Chart in Points

• The primary distinction between a PERT chart and a Gantt chart is that the Gantt chart is a bar chart that provides an exact prediction of the amount of time required to complete each task, and it is only suitable for use in relatively modest projects. On the other hand, a PERT chart uses a flow diagram to determine the total duration of the project, and it is suitable for use in both large and complex projects.
• Comparatively, PERT charts are sophisticated network diagrams that may at times be difficult to understand, whereas Gantt charts are plain and easy.
• The Gantt chart is unable to depict the networks of interrelated tasks, however, the PERT chart is capable of doing so.
• The critical route of a project may be seen with the help of a Gantt chart, whilst project managers can see the critical path shown on a PERT chart.
• A bar chart is used for the Gantt chart, and the length of the bar and its location on the chart are used to describe the beginning date, the ending date of the activity, and the amount of time that the activity will take. The PERT chart is similar to a flow chart or network diagram in that it makes use of boxes and arrows to illustrate the tasks as well as the relationships between them.
• Henry Gantt came up with the idea for the Gantt Chart in the years between 1910 and 1915. On the other hand, in the 1950s, the United States Navy was the first to use what is known as a PERT chart or PERT network diagram.
• In the Gantt chart, the tasks or activities may each be assigned a precise amount of time, but there is no way to supply a set amount of time. The time estimates are used to illustrate each job.
• Gantt Charts provide for the accurate determination of time duration as well as the proportion of work that has been completed, while time estimates are derived from historical data and forecasts.

Conclusion

Both of these tools for managing projects each offer their own set of features and advantages that are useful for analyzing, planning, and scheduling the project. PERT charts are often preferred over Gantt charts because they explain the connections between the activities more clearly. However, PERT charts are more difficult to read when it comes to big and complicated projects.

In a similar vein, the Gantt chart, even though it offers enough information on the punctual completion of each job, is incapable of displaying the interdependency that exists between the tasks and the critical route in a project.

Therefore, the PERT chart will be more suitable for use during the planning phase of the project, whilst the Gantt chart will be the ideal option when the project is already underway so that members of the team will have a clear view of what their respective roles are.

References

1. https://pmworldlibrary.net/wp-content/uploads/2013/04/pmwj9-apr2013-weaver-where-misuse-terms-gantt-PERT-commentary.pdf
2. https://pdfs.semanticscholar.org/efa0/69779cfeeb1e8a57f1e66359ac72abc0ca6e.pdf