All projects, be they big or small, have multiple data points that stakeholders need to see- timeline, expenses, efficiency and more. Gantt charts are a specialized type of bar charts that illustrates a project schedule. Project management and Gantt charts are inseparable. In fact, Henry Gantt – the creator (and namesake) of Gantt charts is also credited with being one of the forefathers of project management (along with Henri Fayol).

A Gantt chart is used for showcasing timelines. It is a date/time-based chart that allows plotting tasks with their exact start and end date/time. Milestones can also be defined to assert how much of the project should be completed by when. Broadly, this chart looks like an extended version of the bar chart. The chart canvas is divided into a view pane and a data table. Tasks and their start and end date/time are listed in the view pane. Horizontal bars, representing tasks, are shown in the data table. The length of the bar represents the duration of the task. Arrows are used to connect tasks and stars or polygons are used to represent milestones.

One of the first Gantt charts ever made were used for WW1 Navy shipbuilding activities for the United States. The rise in efficiency was so high that Gantt charts were quickly adopted in a lot of government projects including the building of the Hoover Dam as well as the US Interstate Highway.

However, projects themselves have changed drastically since the Gantt Charts were introduced more than 100 years ago. While time still is a very important viewpoint, there are other perspectives that project owners and managers have, especially when it comes to building software projects, which are much more fluid than their traditional counterparts; like construction, mining or even manufacturing. Due to this, Gantt charts are not always the best option for showing progress plan and progress to stakeholders.

In this article, our in-house dataviz experts have helped us figure out what are the best scenarios to use a Gantt chart, and the other times when it’s best to use an alternate visualization.

When is Using a Gantt Chart not a good idea

When you need to see the amount of work done

Each bar on a Gantt chart indicates the time period over which a particular set of tasks will be completed. However, by looking at the bar for a particular set of tasks, you cannot tell what level of resources are required to achieve those tasks. So, a short bar might take 500 man hours while a longer bar may only take 20 man hours. The longer bar may indicate to the uninformed user that it is a bigger task, when in fact it is not.

When you need a simplistic view of your data

In a lot of larger scale projects there will be a large number of tasks undertaken and resources employed to complete the project. However, when the project gets to this level, it must be managed by a small number of people (perhaps one) who manages all of the details. Sometimes this does not work so well in a business that is not used to this type of management. Big businesses will frequently employ one or more project managers who are very skilled in this. For a range of reasons, this may not work so well in a smaller enterprise.

When you haven’t completed the planning

The biggest limitation of a Gantt chart is that it relies upon the work breakdown structure to have already been constructed – and for it to be complete. Should there be major tasks missing from the WBS, or should a major milestone be missing, the Gantt chart will not showcase the same to you. In fact, if you are attempting to create the work breakdown structure at the same time you are constructing the Gantt chart, you’ll run into the risk of having to recreate the entire project schedule if something is left out, a duration is mis-estimated, or another milestone has been missed.

Kanban boards are great for handling flexible and iterative projects instead of the Gantt Charts, which are better suited for rigid, well-defined projects 

When you want to see the scope and cost of a project

Gantt charts do not do well with dealing with the triple constraints of Project Management. The triple constraints are: Time, cost, and scope. Neither the cost nor the scope of a project is depicted on a Gantt chart. Due to this no matter how detailed the Gantt chart is, the full complexity can never be depicted. This is because the focus of the Gantt chart is only time.

Scroll along the chart to see time and scope constraints for the same project

When is Using a Gantt Chart a really good idea 

When you want to look at the time various parts of the projects will take

One of the greatest reasons any project manager should use a Gantt chart is the Time-centric guidance provided by the powerful and meaningful insights the chart gives. As an example, you can get the total amount of time it will take you to accomplish the project. Further, a Gantt chart not only gives you the possibility to visualize a sequence of events planned in your schedule, but it also enables the creation of a link between activities, also known as “dependencies”, allowing identification of the the tasks that might get affected by another task.

When you have a concrete plan shelled out for the project

Gantt charts allow you to set accurate deadlines. When you are scheduling the whole project you are able to enter a starting date, a target end date, all the key dates or milestones in the middle and even set a duration for each task. The whole project is scheduled and everything looks good so far. But what if something comes up unexpectedly? That is when using a Gantt chart becomes really interesting. When starting a project, there’s a great chance that unexpected events will come up and have an impact on your schedule. A Gantt chart enables the scheduler to be very flexible, react quickly to unforeseen events, and modify the schedule basis project changes. Gantt charts make it possible to develop visual scenarios to react very quickly to those unforeseen events, for instance, what happens to the second milestone if the first task takes a week longer? That way, reactions to quick changes on the schedule can be visible.

When you need to allocate resources dynamically

By being able to look ahead on the Gantt chart, users can clearly discern where resources need to be anticipated, allocated or shared to maximize the use of those resources. The more closely the chart is followed, the better are the chances of keeping project costs within budgets, while also ensuring on-time completion. With a Gantt chart you will have, at your disposal, a very clear view of all the activities scheduled, how long each activity is scheduled to last, where do activities overlap with other activities, and where each resource is placed. All you need is a few minutes to think about it and affect the right resource to the right task, and ensure that you aren’t wasting resources with under optimised allocations.

When you have to manage inter-dependent tasks

Gantt charts can make it very clear how various tasks are interrelated, and perhaps rely on the completion of another task to meet specific objectives. These task relationships revolve around understanding the timing of each task, which then impacts other tasks listed. This can better assure the optimum work flow, maximize productivity and ensure overall project success. A dependent task is always tied to another one, and you can only start once the first task is completed (there are also other types of dependencies, such as start to start, or finish to finish). Thanks to that you will be able to define the starting point of an activity once the previous one is achieved.

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