Understanding Gantt Vs PERT Chart: 12 Differences & Similarities

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What Is A Gantt Chart?

A Gantt chart is a horizontal bar chart developed as a production control tool in 1917 by Henry Charles Gantt, an American Engineer and Social Scientist.  The Gantt chart is commonly used in project management to provide a graphical illustration of a schedule that help to plan, coordinate, and track specific tasks in a project.

A Gantt chart is constructed with a vertical axis representing the tasks that make up the project  and the horizontal axis representing the total time span of the project, broken down into increments for example days, weeks or weeks.

The horizontal bars of varying length represent the sequences, timing and time span for each task. As the project progresses, secondary bars, arrowheads or darkened bars may be added to indicate completed tasks or the portions of tasks that have been completed.

Usually, in a progress Gantt chart, tasks are shaded in proportion to the degree of their completion: a task that is 70% complete would be 60% shaded, starting from the left. A vertical line is drawn at the time index when the progress Gantt chart is created, and this line can be compared with shaded tasks. If everything is on schedule, all task portions left of the line will be shaded and all task portions right of the line will not be shaded. This provided a visual representation of how the project and its tasks are ahead or behind schedule.

What You Need To Know About Gantt 

  1. Gantt charts were developed and introduced in 1917 by Charles Gantt. It deals with the sequence of tasks needed to complete the project.
  2. A Gantt chart is a type of horizontal bar chart commonly used in project management, which is a visual view of tasks scheduled overtime.
  3. Gantt charts present project tasks and time allocation as the only two pieces of data.
  4. Gantt charts are ideal for straightforward projects with few interlinking tasks.
  5. Gantt charts are easier to change as a task moves along and come closer to completion.
  6. Gantt charts present information in the format of a Bar Chart. This presentation helps show the percentages of work completed for each task.
  7. Tasks in Gantt charts have a single time structure.
  8. Gantt charts do not display the critical and non-critical tasks.
  9. In Gantt charts, the focus is on the percentage completion of each task, without demonstrating the link that two tasks may have to each other.
  10. Gantt chart does not show clear dependencies or relationship between tasks for example, which task comes first, then second or you cannot tell how one task falling behind schedule affects other tasks.
  11. Gantt charts are simpler to read and interpret; they present project tasks and time allocation as the only two pieces of data.
  12. By use of Gantt charts, a manager may not realistically predict how long a task will actually take to complete.

What Is A PERT Chart?

Program Evaluation Review Technique (PERT) Chart also referred to as PERT Diagram is a project management tool used to schedule, organize and coordinate tasks within a project. It is basically a method to analyze the tasks involved in completing a given project, especially the time needed to complete each task and to identify the minimum time needed to complete the total project. The technique was initially developed by the U.S Navy in the 1950s for the Polaris submarine project.

The PERT chart template uses nodes (drawn as rectangles or circles) to represent events and milestones throughout the project. The nodes are connected by vectors (drawn as lines) which represent the various tasks that need to be completed. On the PERT chart, the direction of arrows indicates the flow and sequence of events required for project completion. Dotted activity lines represent dummy activities- items that are located on another PERT path. Number and time allotments are assigned and shown inside each vector.

 Today, PERT charts are used by teams across industries looking to plan and execute their projects more effectively. A PERT chart allows managers to evaluate the time and resources necessary to manage a project. This evaluation includes the ability to track required assets during any stage of production in the course of the entire project.

What You Need To Know About PERT Chart

  1. PERT charts were developed and introduced by the U.S Navy in 1950 to manage large and complex projects.
  2. PERT Chart is an acronym for (Program Evaluation and Review Technique). A PERT chart is a project management tool used to schedule, organize and coordinate tasks within a project.
  3. PERT charts present project tasks, time allocation and dependency among tasks as pieces of data.
  4. PERT Charts are generally ideal for large and complex projects, with many interlinking tasks.
  5. PERT charts are not necessarily easy to change as a task moves along and comes closer to completion.
  6. PERT Charts presents information as a network model (in terms of Flowcharts or Network Diagram). This helps to visualize the sequence of tasks.
  7. Tasks in PERT charts have three representative time structure: optimistic, most likely and pessimistic.
  8. PERT charts clearly display critical and non-critical tasks.
  9. PERT Charts does not show the percentage completed, because it employs a network model in representing tasks and therefore it is easy to see which tasks depend on each other.
  10. PERT has numerous interconnecting tasks that depend on each other.
  11. It is somehow tedious to read and interpret PERT Charts, because PERT charts extend an element of detail to the project scheduling through both the network diagram’s ability to display dependency and PERTs unique ability to anticipate actual time a task will take to completion.
  12. By use of PERT Charts a manager can predict more realistically how long a task will actually take to complete by averaging optimistic, most likely and pessimistic times provided.

Also Read: Difference Between Gantt And Pert Chart

Difference Between Gantt And PERT Charts In Tabular Form

BASIS OF COMPARISON GANTT CHART PERT CHART
Development Gantt charts were developed and introduced in 1917 by Charles Gantt. It deals with the sequence of tasks needed to complete the project.   PERT charts were developed and introduced by the U.S Navy in 1950 to manage large and complex projects.  
Description A Gantt chart is a type of horizontal bar chart commonly used in project management, which is a visual view of tasks scheduled overtime.   PERT Chart is an acronym for (Program Evaluation and Review Technique). A PERT chart is a project management tool used to schedule, organize and coordinate tasks within a project.  
Data Gantt charts present project tasks and time allocation as the only two pieces of data.   PERT charts present project tasks, time allocation and dependency among tasks as pieces of data.  
Usefulness Gantt charts are ideal for straightforward projects with few interlinking tasks.   PERT Charts are generally ideal for large and complex projects, with many interlinking tasks.  
Alterations Gantt charts are easier to change as a task moves along and come closer to completion.   PERT charts are not necessarily easy to change as a task moves along and comes closer to completion.  
Format of Presentation Gantt charts present information in the format of a Bar Chart. This presentation helps show the percentages of work completed for each task.   PERT Charts presents information as a network model (in terms of Flowcharts or Network Diagram). This helps to visualize the sequence of tasks.  
Time Structure Tasks in Gantt charts have a single time structure.   Tasks in PERT charts have three representative time structure: optimistic, most likely and pessimistic.  
Critical & Non-Critical Path Gantt charts do not display the critical and non-critical tasks.   PERT charts clearly display critical and non-critical tasks.  
Percentage Of Completed Task In Gantt charts, the focus is on the percentage completion of each task, without demonstrating the link that two tasks may have to each other.     PERT Charts does not show the percentage completed, because it employs a network model in representing tasks and therefore it is easy to see which tasks depend on each other.  
Relationship Between Tasks Gantt chart does not show clear dependencies or relationship between tasks for example, which task comes first, then second or you cannot tell how one task falling behind schedule affects other tasks.   PERT has numerous interconnecting tasks that depend on each other.  
Reading Of The Charts Gantt charts are simpler to read and interpret; they present project tasks and time allocation as the only two pieces of data.   It is somehow tedious to read and interpret PERT Charts, because PERT charts extend an element of detail to the project scheduling through both the network diagram’s ability to display dependency and PERTs unique ability to anticipate actual time a task will take to completion.  
Prediction Of Task Completion By use of Gantt charts, a manager may not realistically predict how long a task will actually take to complete.   By use of PERT Charts a manager can predict more realistically how long a task will actually take to complete by averaging optimistic, most likely and pessimistic times provided.  

Similarities Between Gantt And PERT Charts

  • Both of these charts are used by project managers and help in displaying the tasks which are required for project completion.
  • The charts are used for task scheduling, controlling and administering the tasks necessary for completion of a project.

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