How to read it
- The rows are the tasks or jobs, often grouped into phases.
- The horizontal axis is time: days, weeks or months.
- The length of each bar is that task’s planned duration.
- The arrows between bars are the dependencies: what cannot start until something else finishes.
An example
Remodeling a store: demolition from the 3rd to the 7th, electrical and plumbing from the 10th to the 21st, painting from the 24th to the 28th. If electrical and plumbing slip a week, the Gantt chart shows at once that painting moves with them, and so does the handover.
What a Gantt chart does not tell you
Whether there are people to do it. A Gantt chart can look perfect and be impossible, because the same person appears on three bars at once. That is why you read it alongside resource utilization.
The usual mistake
Drawing it once and never touching it again. A Gantt chart that does not reflect what happens is a picture of day one. And without a saved baseline, when dates move there is nothing to compare them with.