Gantt Charts as a Tool for Project Management

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Developed by Leonora Charlotte Malabi Larsen

This article is written in connection with course 42433 Advanced Engineering Project, Program and Portfolio Management at The Technical University of Denmark in the autumn of 2015.

A project is a unique set of processes which consist of different activities and tasks to be performed before reaching the project objectivities. During a project unique and complex problems are solved under unpredictable conditions, varying collaborations and great time pressures. All of these characteristics make it incredibly difficult to manage the individual flows of the project. However there are tools that help project managers to manage the project planning and monitoring the schedule to keep track of all activities that needs to be performed. The most common tool is the Gantt Chart because of its simplicity and easy application to any project. It forms a baseline for the lifetime of the project to measure if it is on track or not. Furthermore it helps organizations understand what they are achieving and what they wanted to achieve.

This article aims at providing information about Gantt Charts as a planning/monitoring tool for complex projects and how to apply and benefit from them in project management but also what challenges and limitation there are to the tool. This article is based on the course material as well as literature reviews of scientific research papers and other influential publications on the subject, Gantt Charts, within the academic fields of Advanced Engineering Project, Program and Portfolio Management.


The Big idea

Figure 2: Karol Adamiecki (1866-1933), Source:

The earliest Gantt chart appeared in the 1890s. It was created by a Polish engineer by the name of Karol Adamiecki (Figure 2) who ran a steelwork in the southern Poland. He was in-terested in different ideas and techniques within management. But 15 years later an American engineer, Henry Gantt (Figure 1), came up with his own version of the chart during his work on the construction of Navy ships during world war one. His version of the chart eventually became widely known and popular and therefore Henry Gantt was the one who laid name to the chart. The Gantt chart has changed very little over the past 100 years and is still thought of as an essential project management tool because of the many advantages that the chart provides. [1] [2]

The tool is very commonly used in project management because it gives a clear overview of:

  • What the different activities within the project are
  • When each activity is initiated and when the deadline is
  • How long the activity lasts
  • Overlap between activities and by how much
  • The start and end of the entire project

The main objective of a Gantt Chart is to estimate the duration of a project and to establish the order in which the different tasks that need to be carried out. [3] [1]


Figure 3: Example of Gantt chart, Source: Orr, 2003

Gantt charts used to be prepared by hand and therefore the chart needed to be redrawn every time there was a change in the project which posed some limitations to the usefulness of the chart. However with the invention of the computer along came project management software which makes the tool much easier to handle and update when changes occur. This article will not go into details with the different tools related to making Gantt charts and will merely explain the use of this project management tool and what challenges and limitations a project manager is faced with when using the tool. [1]

The Gantt Chart is build up around three key elements: the grid, the task bars and the time scale. The grid is built up as a matrix consisting of vertical and horizontal lines that cross with one another, creating a number of boxes that represent a single unit of time. The time scale is placed on the horizontal axis and can be set to any time interval be it a day, a week or a month etc. The time interval is most likely to change as planning progresses but can with the use of computer software easily be adjusted.

All activities are listed vertically to the left of the chart. In Figure 3 the tasks have been named: Task 1, Task 2, Task 3 etc. but in real Gantt charts the task description should be meaningful in order to clearly communicate the purpose of the task.

The horizontal task bars are the heart of the Gantt chart. They show where an activity begins and ends. Simple, quick and with a clear visual impact they give a wealth of information. Once the grid has been filled with taskbars and dependencies the chart will hold the majority of the key information needed to analyze and monitor the project as it progresses. [2]

Creating the Gantt chart step by step

Step 1: Identify tasks

The first step in making a Gantt chart is to identify the various tasks that need to be done in order to reach the project objectives. In order to do that the project manager meets with the people involved with the project and gathers information about the main activities that needs to occur in order to complete the project. This result in a very broad plan showing key sequences of events that needs to occur. [2]

Step 2: Analyze tasks

Next up is performing a detailed analysis of the tasks to be undertaken in order to get an understanding of the attributes related with each task. This includes resources, timescale and dependencies. This is important due to the fact that all attributes are linked closely together – adjusting one will affect the other! An example of this could be adding human resources to a task which will result in saving time for completing the task but could increase the cost. The fact that all attributes are linked can make it difficult to know where to begin however the simplest place to start is the task duration. How long a task will take is often estimated by the people responsible for performing the task based on previous experiences with similar tasks from the past and what the requirements are for achieving the task. Having experiences with similar tasks is a huge benefit because it makes it possible to adjust the requirements for achieving the task based on any difficulties that they may have come across before, making the task run more smoothly. [2]


Figure 4: Dependencies, Source: Orr, 2003
Figure 5: Dependencies with lag time, Source: Orr, 2003

The Gantt chart is an amazing tool but on its own it will not ensure the success of a project because of the many challenges a project is met by during its lifetime. It needs to be accompanied by a skillful project manager that can control and monitor the progress of the project and seek to make continuous improvement. In the following section the most important challenges to making a Gantt chart are described and how to handle them.


Some tasks can overlap each other because they don't depend on each other but on the other hand some tasks may be dependent on one another and therefore it can be useful to use indications of dependencies that link related tasks together in the Gantt chart. Dependencies can be described in various ways: finish to start, start to start and finish to finish as shown on Figure 4. They are illustrated on the Gantt chart as small vertical arrows running between the tasks. The most common dependency is finish to start indicating that one task needs to be finished in order for the next to begin. Start to start dependencies means that two tasks are started at the same time however this does not mean that they are completed at the same time. Finish to finish dependencies indicates that the tasks are finished at the same time but the beginning of them can be initiated at different times.

In the practical world when planning a project it can be difficult to rely on dependencies because of sudden changes in the project. To account for this there at two variations of dependency types that can be applied: dependencies with lag time and practical dependencies. [2]

Lag time dependencies

Dependencies with lag time are used where a period of time occurs between one activity completing and another starting. An example of this could be applying for planning permission. Waiting for the approval can take a number of weeks, but ones the approval has been given the work can begin. The time spent waiting to get the approval is called lag time which is time that needs to occur before moving on, see Figure 5. [2]

Partial dependencies

The type of dependency where a task can begin after a certain amount of its prede-cessor task is completed is called a partial dependency. On Figure 5 they are illustrated with blue arrows between the related tasks. [2]

The critical path

The critical path is an important feature of a project that the Gantt chart can help identifying. The critical path is the longest sequence of activities in a project plan which must be completed on time for the project to finish on schedule. The tasks included in the critical path are called the critical tasks. An activity on the critical path cannot be started until its predecessor activity is complete. If it is delayed for a day, the entire project will be delayed for a day unless the activity following the delayed activity is completed a day earlier. On Figure 5 it can be seen that Task 4 is the latest task to be completed in week 17. The series of activities leading up to week 17 is task 1 followed by task 2 and task 3. These four tasks are the critical path of the project illustrated on Figure 5. Because of the importance of the critical path for the projects progress, project man-agers usually highlight the path on the Gantt chart, on Figure 5 it is highlighted in red. [2]


The tasks that are not on the critical path have what is called float attached to them which is the difference between the time available to complete the task and the time required, illustrated as punctured bars on Figure 5. It is also the time in which a task can be delayed without it influencing the end date of the project. If a task has no float then it is on the critical path of the project. On Figure 5 the tasks that have the most float is Task 8 and 7. A subset of float is called free float and it only applies to tasks which have a successor that is not on the critical path. It is the maximum amount of time that a task can be delayed without delaying any successor task beyond its start date. An example of free float on Figure 5 is Task 6. On Figure 5 the yellow diamonds show milestones which are point in time where a bigger event will be completed if everything goes as planned. [2]

Risk Mitigation

Uncertainty or risk is always a part of project management and it is essential for the project manager to fully understand where problems might occur in order to plan ahead of them an avoid delays and expensive cost to try and make up for it or correct a mistake. Therefore it is a good idea to put in extra time in the schedule for things to go wrong.

There are two ways to ad time for things to go wrong: float, which has been mentioned previously and contingency. These two methods are very different from one another. Contingency is planned time for things to go wrong whereas float is time that is available but if used this means that what was planned has not been achieved. However float does give the advantage of extra time if unplanned events should occur, but it is not a good idea to rely on float alone in the events of things going wrong. Project managers should include contingency in their planning of a project for each task where there is a significant amount of risk for the task not to precede as planned. How much contingency needs to be added depends on how big the risk is.

The challenge with adding contingency is the reluctance that the project manager might meet from the project sponsors because of their wish for the project to finish as quickly as possible. It is common for the project sponsors to suggest that the contingency will be added at the end of the project instead of a task-by-task basis in order to get a feeling of control over the project and finish early. However the contingency should be planned on a task-by-task basis to make sure that the project can cope with unexpected events at that moment when they occur. [2]

Monitoring and control

When the Gantt Chart is approved and the project is initiated it is important to monitor and control the progress of each task to successfully manage the project. This can be done by the project manager by simply asking the project team to report on their work continuously to get an idea of how many percentage of their task is complete. However making sure to get sufficient information about the progress of their work can be difficult if their statement is subjective and with no analysis of the real progress the project has achieved. Therefore it crucial to have a system where the reports have a standard template to ensure that the right information is gathered and up to date. But it is equally important that this infomation is interpreted by the project manager to get the real picture of how the project is doing. This helpt the the project managers make timely actions whether it be to decide if new planning or corrective actions are needed for any of the tasks to avoid problems building up. [2]


Gantt charts can have a great benefit to project managers but they are however limited.

The Chart is based on the work breakdown structure. This method is used to breaking down a project into components or pieces that can be estimated and analyzed to make complex project more manageable. If a project has not gone through a breakdown structure process the Gantt chart cannot be used for the project schedule due to the risk of overseeing vital activities in the project making the Gantt chart useless. [4]

Complexity is the biggest limitation because it is difficult to display them in the Gantt chart. An example could be a milestone that has multiple tasks that are required in order to achieve it. For each of those tasks has sub-tasks is required and this is difficult to explain well in the chart. For this reason the project managers should not rely exclusively upon the Gantt chart.

If a project is very complex the Gantt Chart can become very extensive and confusing instead of creating an overview depending on how detailed the chart is made. If the chart goes past one page the chart begins to loose its functionality which is why the chart works best for smaller projects.

The Gantt charts main focus is time. Trying to ad time, cost and scope is very difficult because the chart is so limited.

Depending on the project other tools than the Gantt chart that might suit the project better.


During the project the chart needs to be updatet because of progress or changes to the project

Annotated bibliography

The annotated bibliography provides key references to relevant subjects related to the Gantt Charts and provides additional information on the subject and why it is relevant:

To find more information on Gantt charts, please have a look at rther related articles written in connection with the course 42433 Advanced Engineering Project, Program and Portfolio Management at The Technical University of Denmark in the autumn of 2015 regarding Gantt charts are:

If you are interested in other subjects relevant to Gantt Charts please have a look at the following articles from the course:

This article adresses how uncertainties and risk are created and how they can be managed by the means of Lean Construction principles.

I also recommend:

Engineering Management Journal (2003), The Institute of Engineering Technology This book provides information on management methods, techniques and processes relevant to engineers, incorporating project management, marketing, finance, law, quality and responsibilities of the engineer in society and was also used for this article.


  1. 1.0 1.1 1.2 [] What is a Gantt chart? Available at: (Acessed: 17-09-2015, 12:30 pm)
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 [Uncharted Territory] Orr, Alan (2003) Engineering Management Journal, Volume 13 issue 3, page 28-31, Glasgow, England
  3. [] How can gantt charts help avoid disaster Available at: (Acessed: 17-09-2015, 01:05 pm)
  4. 4.0 4.1 [] What is a Work Breakdown Structure Available at: (Acessed: 24-09-2015, 10:19 pm)
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