Advantages of Gantt Charts include:
- It gives an easy and visual idea about the status of the project, is it on time or not?
- It tells us who's working on what.
- It shows the dependencies of the tasks.
- It can easily adapt to changes in the project.
- It shows us the total cost of the project.
- It tells us how much, in percentage, of a task is complete (although, as I will later explain, it is misleading in that aspect).
- It is understood by management, as it doesn't need any technical background to understand.
- It doesn't require any skills to create (in most Project Management Software). The project manager just creates the project schedule and the Gantt Chart is created automatically by the software.
- It is universal, every project manager on this planet knows what a Gantt Chart is and what it's used for.
Disadvantages of Gantt Charts:
- It is misleading, for example, it shows that one task is 90% done, for the untrained eye, this means that if the first 90% took 9 hours, then the remaining 10% will take 1 hour. This is wrong in almost every case. In the last 10% of any task, a lot of factors come into play, and on top them the Pareto principle (80-20 rule, where 80% of the task takes 20% of the time, and the remaining 20% of the task will take 80% of the time).
- It can become quite complicated for large projects, nearly impossible to read.
- Dependencies can easily become a mess, especially for larger projects.
- It is nearly impossible to print the Gantt chart on one page, even one big page, for every non-small project. I bet that every project manager has experienced this problem. The workaround used by most project managers is printing the Gantt chart on different papers and then scotch-taping the papers together.