A Gantt chart shows tasks against time. Each task is a horizontal bar; the bar's position shows when it starts, and its length shows how long it takes. Stack the bars up and you can see, at a glance, what happens when and what overlaps.
What a Gantt chart shows
- Tasks — the work to be done, listed down the left side.
- Timeline — dates or weeks across the top.
- Bars — each task's duration, positioned on the timeline.
- Dependencies — arrows or alignment showing that one task must finish before another can start.
- Milestones — key moments, often drawn as diamonds, marking an important point like "design approved."
Dependencies — what makes a Gantt chart useful
The real value is in showing what depends on what. If "build" cannot start until "design" finishes, the chart makes that visible. This is how you spot the critical path — the sequence of dependent tasks that determines the shortest possible project length. Delay anything on the critical path, and the whole project slips.
When to use a Gantt chart — and when not to
Use it when you need to communicate timing, sequence, and dependencies — planning a project, showing a roadmap, explaining why something cannot be delivered sooner.
Do not use it to capture requirements or process logic. A Gantt chart shows when work happens, not what the work must achieve or how a process flows. Reaching for a Gantt chart to describe a process is a common category error.