The Gantt Chart, invented in the early twentieth century by Henry Gantt, conveys a large amount of information instantly. In its simplest form, it is a graphic display of project work with corresponding horizontal bars that represent the duration of the work.
The basic Gantt chart has two sections: activities and task bars. Tasks are scheduled to begin on their early start dates. The length of each bar is determined by the amount of time needed to accomplish the task. Gantt charts, also known as bar charts and schedule charts are the most widely used project management charts. For small projects, the Gantt chart is often used as a stand-alone tool and checklist to ensure that all tasks have been completed.
Used along with the task network, WBS, and other tools, the Gantt chart can be used for planning, tracking, monitoring, and controlling larger projects. But the Gantt chart does not contain enough detail to be used as a stand-alone tool for managing medium-size or large projects. You can also tailor the format of a Gantt chart to meet the information needs of different stakeholders. Software packages offer hundreds of possible formats.
There are two sections in this basic Gantt chart: the list of tasks at the left and horizontal lines at the right, which represent the estimated start and finish dates. The time increments are weeks. Slack is shown by the letter u. Later in the chapter and in subsequent chapters, you will see different types of bars and symbols. Additional data columns will also be added to provide more information. For small projects, a few minutes spent producing a Gantt chart is well worth the effort, and it avoids oversights.
At the top of the Gantt chart is basic information, including the name of the project, project number, date, and initials of the project manager. By using a Gantt chart, you can plot the start, duration, and finish times of all tasks and activities. To create or draw a Gantt chart manually, you need to analyze when an activity is to begin, the number of weeks, days, or hours necessary to accomplish the task, and when it will be finished.
If you have created a task network, or entered the data into project management software, this work has already been completed. Most software can build the outline version of a WBS, and then add durations and task bars, thereby combining the WBS and Gantt chart onto one form. If a color printer or plotter is available, the Gantt chart can be enhanced further by coloring the symbols.
For a small one-person project, you can prepare a Gantt chart with an ordinary sheet of lined paper or on printed Gantt chart forms that will probably be enough to help you plan out your project, as well as serve as a checklist to ensure that all the tasks are done. Planning for a company party would fit this description.
Many software packages that cost less than $100 can make planning and managing these small projects easier still, and a Gantt chart produced by one of these packages is easier to read and to update than a hand-written chart.
It takes five steps to produce a basic Gantt chart for a small project:
1. List the tasks necessary to complete the project on a sheet of paper, or enter them into your project management software application.
2. On the top-right side of your paper, write in the time increments from left to right. If you choose weeks, write the dates for every successive Monday or other day of the week, such as 12/12, 12/19, 12/26, and so on.
3. Estimate the time needed to complete each project task.
4. Identify all predecessor and successor relationships.
5. Manually schedule or allow the software to schedule all tasks, based on the time needed, predecessor and successor relationships, and resources required. Draw or let the software draw horizontal lines or bars to represent the time estimates.
Many formats of the Gantt charts are possible. Different audiences require different information and, therefore, different formats. Senior management does not require or desire detailed information in most cases. On the other hand, project team members need the Gantt chart to display the lowest level of detail available. Team members will want to display the Project ID number, name, WBS number, duration, start, and finish. To report the status and progress to upper management, you would select a summary format. You could select a format that shows the tasks along the critical path and slack time. Of course, by using a project management software program, you can expand or collapse any Gantt chart.
Validating the Gantt Chart
After producing a Gantt chart, you should validate it by asking yourself questions that cover the four most important points:
1. Are all tasks listed?
2. Are durations realistic?
3. Have all predecessor and successor relationships been identified?
4. Do the scheduled dates seem reasonable?
Talk to all project ream members, including suppliers and support groups, to determine if the list of tasks and other data is complete. Even on small projects, it is likely that there will be additions and changes after the project begins. For bigger projects it is easier to read and use if it is sorted by critical path and in chronological order for non-critical tasks. This allows you to check for near-critical tasks, sequence errors, and gaps.
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