gantt chart

Today we are going to discuss the Gantt chart, which is the most important tool in schedule management. The Gantt chart helps project management immensely in controlling and managing the schedule.

What is a Gantt Chart?

Many people think Henry Gantt developed the Gantt chart as it was named after him. But this is not true.

The Gantt chart is a bar chart developed by Karol Adamiecki, a Polish engineer, in the mid-1890s and he called it harmonogram but it did not become well-known outside of Poland and Russia. 15 years later, Henry Gantt, an American engineer, got the same idea and developed the Gantt chart for his production work to track progress. It became popular in Western countries and therefore known as the Gantt chart after Henry Gantt.

These charts are easy to read and therefore commonly used in projects when a graphical representation of schedule is required.

The Gantt chart has evolved; it is now more advanced and shows the various dependencies between the activities and the schedule status.

Gantt charts help project managers manage project activities until the project ends.

Benefits of Gantt Charts

Schedule deviations are quite common in projects, and the Gantt chart allows the project teams to take corrective actions and align themselves to the planned milestones.

Gantt charts have many benefits, and a few of them are as follows:

  • Easy to create
  • No learning curve
  • A good communication tool
  • Avoids resource overload
  • Monitors project progress
  • Promotes transparency
  • Creates accountability
  • Improves productivity
  • Helps manage resources

Construction of a Gantt Chart

Gant chart is a kind of bar chart, where:

Vertical axis: The tasks are listed on the vertical axis

Horizontal axis: The width of bars on the horizontal axis shows the activity duration.

Let’s construct a Gantt chart! 

Here below is a step-by-step procedure.

Step 1: List down the activities planned for a work package as part of the WBS (Work Breakdown Structure).

Let’s consider a sample work package below for a simple project to design a logo for a product:

I am marking the activities alphabetically. This would help for preparing the schedule network diagram and for calculating the critical path.

  1. Design
    1. Analyze the tool/software for the design (A)
    2. Prepare sample logos (B)
  2. Testing
    1. Validate logo (C)
    2. Provide QA sign-off (D)
  3. Review & Approval
    1. Review the logo designs (E)
    2. Finalize the logo (F)
    3. Approve the logo for product use (G)

Step 2: Estimate duration for all these activities, for the Optimistic, Pessimistic, and Most likely time expected (I have considered business days in the below table).

ActivityOptimisticPessimisticMost Likely
Analyze the tool/software for the design (A)243
1.2 Prepare sample logos (B)364
2.1 Validate logo (C)132
2.2 Provide QA sign-off (D) 122
3.1 Review the logo designs (E)243
3.2 Finalize the logo (F)132
3.3 Approve the logo for product use (G)0.521

Step 3: Calculate the Total Estimate for each of the above activities, using the PERT Beta Probability Distribution formula:

               Te = (O + 4M + P) / 6

ActivityOptimisticPessimisticMost LikelyTe
Analyze the tool/software for the design (A)2433
1.2 Prepare sample logos (B)3643.67
2.1 Validate logo (C)1322
2.2 Provide QA sign-off (D) 1221.83
3.1 Review the logo designs (E)2433
3.2 Finalize the logo (F)1322
3.3 Approve the logo for product use (G)0.5211.08

Step 4: Identify the predecessor for the activities

ActivityPredecessorOptimisticPessimisticMost LikelyTe
1.1Analyze the tool / software for the design (A)2433
1.2 Prepare sample logos (B)A3643.67
2.1 Validate logo (C)B1322
2.2 Provide QA sign-off (D) B, C1221.83
3.1 Review the logo designs (E)D2433
3.2 Finalize the logo (F)E1322
3.3 Approve the logo for product use (G)F0.5211.08

Step 5: Identify the critical path using a schedule network diagram

A -> B -> C -> D -> E – > F -> G:    Total Duration:   16.58 days (Critical Path)

A -> B -> D -> E -> F -> G:     Total Duration:  14.58 days

Step 6: Now, translating these details into the chart yields a result as seen below:

For non-working days, the duration looks longer, but in reality, only the working days are used for project planning. 

Gantt charts also shows the progress of the project schedule. You can see the completed work on the Gantt chart as shown in the shaded area on the left side (green colored area) of the below chart:

The above chart provides a visual presentation of the project schedule. You can see if the project is on schedule, ahead, or lagging behind schedule. Such a view allows the project manager to take preventive or corrective actions as necessary. Gantt charts can also include the names of the team member working on each activity.

A Gantt chart shows milestones with a diamond shape.

Uses of the Gantt Chart

You can use the Gantt chart for project planning. These days modern software makes it easy to develop a complex Gantt chart. On a Gantt chart you can see:

  • Scheduled work
  • Completed work
  • Project start and end date
  • Team member assignment
  • Task duration
  • Task dependency
  • Etc.

All project management software, task management platforms, and CRM platforms use the Gantt chart in one form or another.

The Gantt Chart’s Limitations: 

In the above statements, we understood the Gantt chart’s various uses. There are few limitations also. 

  1. Gantt charts may not be helpful in complex projects where the work packages have many activities and many dependencies among them. In this case, the Gantt chart would become clumsy.
  2. Though the Gantt charts show the expected activity duration, it does not help to find the resources required to complete the task.
  3. There is little to no flexibility in project planning using the Gantt chart.
  4. For any change in the project plan, it is difficult to update the Gantt chart and time-consuming.
  5. Though activity duration is estimated before developing the Gantt chart, no rationale can be seen on the Gantt chart for this estimation.
  6. A Gantt chart does not show the impact of the delayed activity.

Conclusion

You must keep a project on track, foresee any delays, and swiftly perform preventive or corrective actions to bring the project back on schedule.

A Gantt chart can help you do that. Gantt chart is a bar chart to show the project schedule. These days, you will find many software tools that have made Gantt charts simpler compared to the manual effort. 

While the Gantt chart may not be the perfect tool to assist a project manager in capturing all the details for the project schedule, it definitely helps guide the manager to make informed decisions on the schedule.

Please share your experience on using Gantt charts in your projects in the comments section.

In the PMBOK Guide 6th Edition, the Gantt chart is mentioned is Bar chart at several place. You may see a few question in your PMP exam from this topic.