Note: The original Gantt chart developed by Henry Gantt in 1910 was not the same as the one we use today; it actually showed resources against time (but that’s a topic for another blog post). Today we are interested in how we can use a modern day Gantt chart to plan and control our projects.
There are many different techniques and tools that a project manager can use to control a project schedule on a day-to-day basis and for managing dependencies, change and risks. However, it is important to distinguish between techniques and tools so you understand the technique before using a software tool. The ability to use a software tool is not necessarily an indication of a detailed knowledge of, or effective use of, the technique behind it.
What is a Gantt Chart?
The underlying concept of a Gantt chart is to map out which tasks can be done in parallel and which need to be done sequentially. If we combine this with the project resources we can explore the trade-off between the scope (doing more or less work), cost (using more or less resources) and the time scales for the project. By adding more resources or reducing the scope the project manager can see the effect on the end date.
A Gantt chart displays information visually as a type of bar chart in a clear and easy-to-understand way and is used for the following activities:
- Establish the initial project schedule
- Allocate resources
- Monitor and report progress
- Control and communicate the schedule
- Display milestones
- Identify and report problems
To create a chart you need to know all of the individual tasks required to complete the project, an estimate of how long each task will take and which tasks are dependent on others. The very process of pulling this information together helps a project manager focus on the essential parts of the project and begin to establish a realistic timeframe for completion.
Find out more about gantt charts with APM: What is a Gantt chart?
Disadvantages of a Gantt Chart
But Gantt charts are not perfect and all too often they become overly complex with too many dependencies and activities. This is a trap many new project managers fall into when they start using planning tools. It is much better to produce a clear and simple plan that shows the main work packages in summary, than a plan with so much detail the overall impression of project progress is lost. Let the work package manager put together the day-to-day detail of the activities within a work package, while the project schedule concentrates on the interfaces between project teams.
Neither are they good at showing the relative priorities of individual tasks and the resources expended on a task. Tasks are prioritised on the amount of float not their importance to the project. For example, they can clearly show the elapsed time of a task but cannot so easily communicate how many people may be needed to complete that task. So if not backed up by other data they can give a misleading impression to stakeholders. This is where using additional techniques such as a precedence diagram (sometimes called a PERT chart), for instance, becomes useful
A precedence diagram is another powerful project management technique which is particularly useful for identifying complex inter-dependencies and showing relative priorities of activities and, hence, highlighting the tasks most critical to project success.
Other blogs in this series:
- Project management – an introduction
- Project management processes and phases
- Business requirements and project managers
- People and behaviours in project management
This is a project management fundamentals blog written and sponsored by Parallel Project Training. For more about our project management training courses visit our website or visit Paul Naybour on Google+.