Gantt charts (HL only)

A Gantt chart is used as a visual organizational planning and decision-making tool to show the sequence and schedule of all the different tasks for a certain project. The idea was created by American mechanical engineer and management consultant Henry L. Gantt (1861 - 1919).

A Gantt chart organizes all the tasks of a project into chronological order, and identifies any tasks that can be done concurrently in order to minimize the time needed to complete the project. Scheduling individual tasks also enables managers to have better project management, in terms of monitoring and control. Essentially, the tool enables managers to identify the fastest time in which a project can be completed if the individual tasks are well-planned and executed effectively.

To construct a Gantt chart, several steps are necessary:

• Identify all the various tasks, plus the duration, that need to be completed, arranging these in chronological order.

• Identify any tasks that can be completed concurrently.

• Establish dependent tasks in order to sequence the various tasks, i.e., recognise which activities must be completed before the next one(s) can begin.

• Determine how long the project should take to complete.

An example of a Gantt chart is shown below, which shows a simplified version of the activities needed for construction of an extension (enlargement) to an existing office building:

Note that the project, when presented in the format a Gantt chart shows the project can be completed in 17 weeks. If the tasks were done individually without planning, the sum of the separate tasks equals 20 weeks.

Typically, managers will shade in (manually on a display board, or via computer software) the Gantt chart to indicate the level of progress. For example, the shading shown here indicates the activity has been half completed:

 Advantages of Gantt charts

The advantages of using Gantt charts as a Business Management tool to support organizational planning and decision-making include:

• A Gantt chart helps project managers to have a clear overview of the whole project, in terms of timing and resourcing needs.

• It helps to identify the minimum amount of time required to complete a certain project.

• It helps managers to identify which tasks can take place at the same time, thereby making efficiency gains.

• As a visual planning tool, it provides a clear representation of the current progress of each task in a project.

• Gantt charts can be used for many different scenarios for scheduling and project management purposes.

• Realistic deadlines can be set and resourcing needs (such as people, machinery, and finance) can be arranged for the various tasks of a project.

• The Gantt chart enables managers to prioritise and commit resources to tasks that are most time sensitive or urgent.

 Disadvantages of Gantt charts

However, there are also shortcomings of Gantt charts as an organizational planning and decision-making tool. These limitations include:

• The usefulness of a Gantt chart is dependent on the accuracy of the information used to create it. Inaccurate and unrealistic schedules make Gantt charts rather meaningless.

• The length of each bar indicates the expected duration of the task only; it does not show the amount of work involved or the amount of resources required for each of these activities.

• Gantt charts are not prescriptive nor precise, so need to be constantly monitored and updated accordingly. For example, a delay in one task will have knock-on effects on all activities that follow.

• Gantt charts are meant to be simplistic (their strength), but this means that complex projects with interconnected tasks can be problematic to display succinctly on a Gantt chart.

  Top tip!

As with all quantitative techniques, the value of Gantt charts depends on the underlying data collected and used. When evaluating the use of Gantt charts, consider what the data do not reveal, and not only the outcomes shown by the tool for a particular situation or project.

  Top tip!

Whilst it is possible that students can be asked to construct a Gantt chart in the examinations, it is (statistically) more likely that they will be asked to discuss the value of the tool (considering both the advantages and limitations/drawbacks of the tool). This is because it can be too time consuming to ask students to construct a Gantt chart from scratch under exam conditions (for the same reason that students are not required to construct a critical path or network diagram).

Instead, a Gantt chart might be presented in the stimulus and students are asked to use the chart to address a particular question and/or to evaluate its merits as a planning tool.