Gantt Charts
1. Introduction
A Gantt chart is a visual project planning tool that shows tasks over time.
It helps project managers see:
- When each task starts and ends
- How long it takes
- Which tasks overlap or depend on each other
Originally developed by Henry L. Gantt (1910s), it remains one of the most widely used tools in both plan-driven and Agile-adapted contexts.
2. Structure and Components
A Gantt chart is essentially a time-scaled bar chart:
| Element | Description |
|---|---|
| Tasks / Activities | Rows — represent units of work (from the WBS). |
| Time Axis | Columns — show calendar days, weeks, or sprints. |
| Bars | Horizontal — show duration of each task. |
| Dependencies | Show which tasks must finish before others can start (e.g., after A1). |
| Milestones | Zero-duration events marking key dates or deliverables. |
| Progress / Status | Often indicated with shading or color. |
3. Purpose and Use
Gantt charts serve to:
- Communicate the project timeline to stakeholders.
- Track progress against planned dates.
- Identify delays or bottlenecks.
- Support coordination between parallel activities.
They are often used together with:
- Work Breakdown Structure (WBS) — defines what must be done.
- Activity network / Critical Path — defines what must happen when.
- Milestone plan — defines what is delivered when.
4. Gantt Charts in Different Contexts
| Context | Use |
|---|---|
| Plan-oriented (e.g., Waterfall) | Created early, used to control execution; detailed dependencies. |
| Agile / Scrum | Simplified or rolling-wave versions; visualizing sprints, releases, or burndown trends. |
| Hybrid | High-level Gantt for major milestones, Agile boards for iteration detail. |
5. Example
gantt
title Example Software Project
dateFormat YYYY-MM-DD
excludes weekends
section Planning
Requirements :a1, 2025-10-27, 5d
Design :a2, after a1, 4d
Design Complete :milestone, m1, after a2, 0d
section Development
Backend Module :b1, after m1, 7d
Frontend Module: b2, after m1, 7d
Integration :b3, after b1 b2, 3d
Integration Done:milestone, m2, after b3, 0d
section Testing
System Test :t1, after m2, 5d
Release :milestone, m3, after t1, 0d
6. Strengths and Limitations
| Strengths | Limitations |
|---|---|
| Simple and visual | Becomes cluttered for large projects |
| Shows dependencies clearly | Doesn’t show resource constraints |
| Easy progress tracking | Doesn’t handle uncertainty well |
| Communicates milestones | Hard to maintain manually |
7. Relation to Other Concepts
| Concept | Relationship |
|---|---|
| Critical Path | Longest chain of dependent tasks; often highlighted in red. |
| Merge Path Bias | Gantt charts can hide slack merging; critical chain refines this. |
| Critical Chain | Extends Gantt by including resource constraints and buffers. |
| Milestone Plan | Gantt visualizes milestones in time context. |
8. Tools
Open source Gantt tools:
- Ganter – web-based, open source Gantt manager.
- ProjectLibre – desktop, MS Project compatible.
- GanttProject – cross-platform Java application.
- Mermaid.js – lightweight, code-based diagrams.
- Redmine / OpenProject – integrated project tracking with Gantt visualization.
Disclaimer: AI is used for text summarization, explaining and formatting. Authors have verified all facts and claims. In case of an error, feel free to file an issue or fix with a pull request.