The Gantt chart was developed by Henry Gantt to make it easier for supervisors to determine whether work was proceeding on schedule, and to identify any areas of a project currently suffering delays. The tool has developed over the years until it is now represented as a horizontal bar chart, where each bar represents an activity and the ends of the bar signal the start and end time of the activity. As such, the horizontal axis of a Gantt chart displays the time scale, which can be in the form of a standard calendar, or can be the duration of time from the beginning of the project. Each task has its own bar, with the bar for a task starting once the preceding task has finished, and ending once the task is scheduled to have been completed.
Whilst simple Gantt charts will consist of a sequence of bars with one finishing when the previous one completes, charts for more complex projects will tend to have overlaps. This can be because some tasks may start before previous ones are completely finished, and there may be parallel sequences of tasks occurring at the same time. The Gantt chart is most useful in cases such as this, as it can be used for tracking various parallel sequences of tasks and determining if any are likely to cause delays to the overall completion of the project. It is also possible to use more than one Gantt chart for tasks within a project, effectively splitting the Gantt chart for the main project into a series of charts for each major task.
The basic version Gantt chart simply lays out how the project is planned to proceed. However, modern computer technology and project management software allows the chart to be enhanced to provide more functionality and information. This can also be achieved in physical charts, however the editing process can be time consuming particularly if a project encounters delays. The most common enhancements are:
- The use of a marker to indicate the present point in time
- Shading a bar as a task progresses, and marking tasks as complete once they have finished
- Adding links and colour coding to indicate dependent tasks
- Specifying the resource allocation to different tasks
- Marking key milestones
- Highlighting the critical path: the path that determines the duration of the entire project
- Highlighting any tasks which are delayed or need to be focused on
- Most computer programmes can recalculate the critical path and the amended duration of the project in the event of any delays
When constructing a Gantt chart, it is usual to use the WBS tasks as the basis for creating the chart. However, some smaller projects may not have a specific WBS, and the Gant chart can simply display the identified tasks. The Gantt chart not only displays the duration of each activity, but also allows a quick and easy method of determining the status of a project.
On top of our MBA help guides we also have a range of free resources covering the topic of project management: