A Gantt chart is a planning tool that shows a project's tasks as bars along a horizontal timeline. Each bar marks when a task starts, how long it runs and when it ends, while arrows between bars show which work is waiting on which. At a glance, the team can see who delivers what and when, and which tasks a single delay will push back.
Key takeaways
- A Gantt chart brings tasks, durations, dependencies and milestones together on one timeline.
- A sound Gantt plan rests on five foundations: scope, a task list, duration estimates, dependencies and milestones.
- Panorama Consulting's 2026 ERP Report found that almost a quarter of organisations saw their project run over schedule.
- A Gantt chart is not a one-off drawing; if it is not updated as things slip, it misleads the team.
- Project software that reschedules dependent tasks automatically and highlights the critical path takes most of the effort out of keeping the plan current.
Why use a Gantt chart, and what does poor planning cost?
Projects rarely fail because of one big mistake. They slip through small delays that nobody notices in time: a sign-off arrives two days late, the next team waits, the testing week gets squeezed. In email threads and scattered spreadsheets this chain stays invisible; the problem only surfaces once the deadline has been missed. Catching these slips before delivery is covered in AI project risk early warning.
The pattern is common in larger business projects too. Panorama Consulting's 2026 ERP Report found that more than a quarter of organisations went over budget and almost a quarter went over schedule, with a median project timeline of 9 months. The report names organisational rather than technical issues as the most common cause of schedule overruns. We explore the same patterns in why ERP projects fail.
A delay costs more than a late handover: idle teams, penalty clauses and deferred revenue all land on the bill. That is why schedule risk deserves its own line when you estimate software project cost. A Gantt chart is the most widely used way to make that risk visible.
What are the main parts of a Gantt chart?
Named after Henry Gantt, the American engineer who popularised this kind of chart in the 1910s, the format works with the same building blocks in almost every project tool today:
- Task bar: runs between a task's start and finish dates; its length shows the duration.
- Dependency arrow: shows the order between two tasks; the most common link is "finish to start".
- Milestone: a zero-duration moment that matters, such as client sign-off or go-live, usually drawn as a diamond.
- Progress: the bar fills up to show how much of the task is done.
- Today line: a vertical line that shows where you are in the plan.
Dependencies are not always "one finishes, the next starts". Some tasks start together, some finish together, and there may be a waiting period or an overlap between them. Getting this distinction right from the start decides whether the chart reflects reality.
How does a Gantt chart differ from a kanban board or a task list?
The three views show the same work through different questions. Which one you choose depends on the question the team needs answered at that moment:
| View | Question it answers | Strength | Weakness |
|---|---|---|---|
| Gantt chart | When will it finish, and what is it waiting for? | Time, sequence and knock-on delays in one place | Tedious to maintain for small, fast-changing tasks |
| Kanban board | What stage is each piece of work at? | Shows flow and bottlenecks | No dates or dependencies |
| Task list | Who has what, and when is it due? | Fast, simple, easy to filter | Hides how tasks relate to each other |
In practice, the best results come from a setup where the same tasks appear in all three views. The team runs its daily work on the kanban board, while the manager tracks delivery risk on the Gantt chart. To tell the critical tasks apart, the critical path method is the natural companion to a Gantt chart.
How do you make a Gantt chart, step by step?
The sequence below works the same way on paper, in a spreadsheet or in project software:
- Write down the scope and deliverables. Be clear about what will be handed over at the end; a vague scope produces a vague plan.
- Break the work into tasks. Each task should be small enough for one person or team to own; split long tasks into subtasks.
- Estimate durations in working days. Agree estimates with the people doing the work and allow for weekends and public holidays.
- Set up dependencies. For every task, ask "what has to finish before this can start?" and draw the links.
- Add milestones. Mark moments such as sign-offs, payments or go-live, and report progress against them.
- Assign owners and share the plan. Every bar needs an owner; share the plan with the team and, where relevant, the client.
- Update it weekly. Record actual dates and reschedule the successors of anything that has slipped.
Your task list comes from your scope. To pin the scope down, see our guides to software requirements analysis and writing technical specifications.
A Gantt chart example: a company website project
Take a website project with six tasks. Durations are in working days and the day count starts at zero:
| Task | Duration (working days) | Predecessor | Start day | Finish day |
|---|---|---|---|---|
| A. Requirements gathering | 3 | – | 0 | 3 |
| B. Design | 5 | A | 3 | 8 |
| ◆ Design sign-off | 0 | B | 8 | 8 |
| C. Content preparation | 6 | A | 3 | 9 |
| D. Development | 8 | Design sign-off | 8 | 16 |
| E. Content entry | 2 | C, D | 16 | 18 |
| F. Testing and go-live | 2 | E | 18 | 20 |
On the chart, B and C appear as parallel bars starting on the same day. Design sign-off is marked with a diamond. The project takes 20 working days.
The real value shows when something changes. If design overruns by three days, sign-off, development, content entry and go-live all move three days later. Content preparation, however, has spare time, so its delivery date stays the same. In a spreadsheet kept by hand, you would have to redo this rescheduling every time.
What mistakes do people make with Gantt charts?
The most common mistake is drawing the plan at kick-off and never opening it again. Tasks overrun and new work appears; a chart that is not updated gives the team wrong dates and quickly loses their trust. A short weekly update meeting is enough for most projects.
The second mistake is leaving dependencies out. Unlinked tasks look independent, so the plan comes out shorter than it really is. The third is too much detail: putting hour-long jobs on a Gantt chart makes it unreadable, so leave those to a checklist or a kanban card. How to set up the board is covered in what is kanban.
The fourth problem is running the plan in spreadsheets. It works for small projects, but fixing formulas and colours by hand after every change takes time, and several copies of the file end up in circulation. We cover these limits in outgrowing spreadsheets. For work that happens on site, our guide to construction project management software is also worth a look.
How does SmartPM make Gantt charts easier?
SmartPM is the web-based project management software in Digital Bridge's Smart family. Tasks are managed in list, kanban and Gantt views from the same data, so a card the team moves on the kanban board is also up to date on the manager's Gantt chart.
On the Gantt chart, you move a bar by dragging it and extend it by pulling its right edge. There are four dependency types: finish to start, start to start, finish to finish and start to finish. Lag is set in working days, a negative value pulls the work earlier, and the system rejects any link that would create a loop. Weekends are not counted as working days, and working days can be set per project for teams that work Saturdays.
If a predecessor overruns or moves, its successors are pushed forward with their durations kept intact, and the screen tells you how many tasks moved. The critical path view switches on with one click: critical tasks turn red and every other task shows its float. Milestones appear as diamonds, and subtasks up to five levels deep are indented.
Scenario: an agency sets up the website project above using SmartPM's ready-made website template. The design task runs three days over because the client's sign-off is late. When the project manager extends the bar, development, content entry and go-live move forward together, while the content task, which has enough float, stays put. The team clicks "Request approval" on the design task it has marked as visible to the client; the client sees only the tasks shared with them and replies with Approve or Request changes.
If you are starting from nothing, AI-assisted features speed up the first draft. Upload a document such as a proposal or specification and its work items become cards with durations and dependencies; or describe the project and get suggested tasks, durations and milestones. See every feature on the SmartPM product page.
How can Digital Bridge help?
Digital Bridge treats project management as a way of working, not just a software licence. When we set up SmartPM, we plan which ready-made template to start from, roles (manager, member, viewer, client) and working days with you. If you use other Smart products too, you work with a single account under Smart360.
If an off-the-shelf tool does not fit your workflow, we build planning screens tailored to you through our custom web software service. For projects delivered by outside contractors, our guide to supervising software contractors will help you keep the schedule on track.
Next step: build your first Gantt plan
Take a current project and list its tasks, durations, dependencies and milestones today; that list is the skeleton of your Gantt chart. Rather than fixing the plan by hand after every slip, you can keep it live in SmartPM with automatic rescheduling and the critical path view.
To buy SmartPM, fill in the SmartPM sales form and our team will plan the right setup for your organisation with you. For questions, visit our contact page, or browse more guides on the software topic page. Our definition of a KPI is also useful when you start measuring progress.