Gantt Chart


A Gantt Chart is a horizontal bar chart used in project management as a tool for graphically representing the schedule of a set of specific activities or tasks. The horizontal bars indicate the length of time allocated to each activity, so the x-axis of a Gantt chart is subdivided into equal units of time, e.g., days, weeks, months.  The y-axis of a Gantt chart, on the other hand, simply lists all the activities or tasks being monitored by the Gantt chart.  A simple look at a Gantt chart should enable its user to determine which tasks take the longest time to complete, which tasks are overlapping with each other, etc.


The Gantt chart was developed as a production tool in 1917 by Henry L. Gantt (hence the name 'Gantt chart'), an American engineer and social scientist.  It has since been a popular and important scheduling tool used in almost all industries.  In fact, a multitude of Gantt chart generating software may be found in the market today.


Gantt charts are used for: 1) planning and scheduling projects; 2) assessing how long it takes to complete a project and its component activities; 3) laying out the order in which the activities or tasks will be carried out; 4) managing inter-dependencies among the various activities or tasks; 5) managing the resources (including manpower) needed to complete simultaneous activities; 6) monitoring the progress of each activity; and 7) facilitating recovery actions to keep delayed activities back on track.


A Gantt chart indicates the following: 1) durations and timelines of the listed activities; 2) the target and actual completion dates of the activities; 3) the cost of each activity; 4) the person or group of persons responsible for each activity; 4) milestones in the progress of the project.


Since a Gantt chart is a graphical tool, it employs symbols to represent various information about a project. These symbols include: 1) the task bar, which is the horizontal bar used to indicate the duration of each activity in the Gantt chart; 2) the milestone marker, which denotes a major turning point in the project such as the release of an approved budget or the launching of a new product; 3) the link line, which shows the relationship between two tasks, such as the fact that one activity can only begin after another one is completed.  The task bar may filled with a different color indicating the proportion of the task that has already been finished.


A Gantt chart may also incorporate a 'Resources' column, which is simply an additional column that identifies the people responsible for each activity.  It may also incorporate a 'Budget' section, which shows a vertical bar chart presenting the target budget and actual costs incurred in implementing the project.


Figure 1. Example of a simple Gantt Chart


In the simple Gantt chart example shown in Figure 1, note the filling of the first two task bars which indicate the amount of work already completed. Note as well the link lines indicating that the next task can only start after the previous one has been completed. In real Gantt charts, more information are indicated, including 'actual dates' for the time lines and the people responsible for the tasks.


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