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What is a Gantt Chart

Also known as: Gantt, Gantt diagram

Definition

A Gantt chart is a schedule in which each task is a horizontal bar on a time scale, so you see what runs together, what waits and when the work ends.

Why it matters

A task list shows what has to be done.

Common mistakes

Building a detailed chart at the start and never updating it.

Related terms

Worked exampleIllustration

The flower shop website on six weeks

A six week website project for a flower shop, drawn as bars on a scale of weeks.

  1. Weeks 1 to 2

    Design of the five pages.

  2. Weeks 2 to 3

    The shop writes the texts, overlapping the design.

  3. Weeks 3 to 5

    Development, which starts after the design is approved.

  4. Week 6

    Testing.

  5. End of week 6

    Launch, a milestone drawn as a diamond, not a bar.

If testing takes one more week, the launch diamond moves one week, because nothing absorbs it. The bars show what runs together, the arrows show what waits.

Illustration

What runs together, and what waits

Six weeks: the texts overlap the design, development waits for the approved design, testing waits for development, and the launch diamond sits at the end of week 6.⁨Week⁩12345678⁨Texts (the shop)⁩⁨Design⁩⁨Development⁩⁨Testing⁩⁨Launch⁩⁨Run together⁩

Six weeks: the texts overlap the design, development waits for the approved design, testing waits for development, and the launch diamond sits at the end of week 6.

Each bar is a task on the weeks it takes. The gold band is where the texts run together with the design, the arrows show what cannot start until something else ends, and the diamond is the launch.

Definition

Each row of a Gantt chart is a task, and its bar runs from the task's start to its finish along a scale of days or weeks. Bars that sit over the same weeks run in parallel. A bar that starts where another ends follows it. A milestone takes no time, so it is drawn as a diamond, not a bar. Today's tools also draw the links between tasks as arrows, a line for today and a fill that shows how much of each bar is done, although the early charts drew no links. The chart is named after Henry Gantt, who designed it around 1910 to 1915. Karol Adamiecki had drawn a similar chart, which he called a harmonogram, around 1896, but he published it in Polish and Russian.

Why it matters

A Gantt chart shows when, and what that means for the finish: which tasks can overlap to save time, which ones wait for others, and how a slip in one bar moves the end date. For a small business owner it is the quickest way to see whether a promised date is realistic, and in a weekly meeting the today line shows at a glance which bars are behind.

Directly related: Project, Milestone, Critical Path.

Improvement tips

  • Draw a milestone, such as the launch, as a diamond with no length, and keep the bars for work that takes time.
  • Mark today with a vertical line and update the fill of each bar every week.
  • Group small tasks under a few phases, so the chart fits on one screen.
  • Show the links between tasks as arrows, so a slip in one bar shows which bars move with it.

Common mistakes

  • Drawing the launch as a bar with a length, so it looks like work.
  • Drawing every task one after another when some could overlap.
  • Adding so many small tasks that nobody can read the chart.

Related terms

Project ManagementBeginner

Project

A project is temporary work with a start and a finish that creates one unique result, such as a new website, within limits of scope, time and cost.

Project ManagementBeginner

Milestone

A milestone is a checkpoint in a schedule that takes no time: the moment a stage is done, such as design approved. A Gantt chart draws it as a diamond.

Project ManagementIntermediate

Critical Path

The critical path is the longest chain of dependent tasks in a project. It sets the finish date: a delay on it delays the project, a gain elsewhere does not.

Project ManagementIntermediate

Dependency

A task dependency in project management is a link where one task cannot start or finish until another does. It sets the order of work and carries delays.

Quick check

In a six week Gantt chart, testing takes one week longer and nothing runs alongside it. What happens to the launch diamond at the end?

Choose an answer

Frequently asked questions

Do I need a Gantt chart before starting my business?
Not for a simple start. It helps when the launch has several parts that depend on each other, such as premises, stock and a website, and you want to see whether the opening date holds.
When does a new business first benefit from using a Gantt chart?
When two or three tasks must overlap to meet a date, or when one supplier's delay would move everything. The chart shows both at a glance.
Can a beginner build a Gantt chart without project management software?
Yes. A spreadsheet with the weeks across the top and a coloured row per task is a Gantt chart. A whiteboard with strips of tape works too.
How does a Gantt chart help when I present a plan to others?
It shows the plan as dates, not promises: when each part starts, what runs in parallel and when the result is ready. Anyone can check whether the timing is realistic.
Why does a Gantt chart matter for a business already running?
A task list does not show how a delay moves the finish. The chart does, so you see which late task matters and which one has room.
What goes wrong when a business creates a Gantt chart but never updates it?
It shows a plan that is no longer true, and people make decisions from it. A chart is useful only while its bars and its today line match what is really happening.
How do I keep a Gantt chart updated without wasting time?
Ten minutes in the weekly meeting: each owner says how far their bar is, you move the fill and the today line, and you note any bar that moved.
My Gantt chart is too cluttered and hard to read. What should I do?
Group small tasks under a few phases and keep only the milestones that matter to the finish. Detailed task lists can live elsewhere.
What is a Gantt chart in simple words?
A calendar of the project in which every task is a horizontal bar. The length of the bar is how long the task takes, and its place on the scale is when it happens.
Is a Gantt chart hard to understand for a beginner?
No. Read it from left to right: bars over the same weeks run together, and a bar that starts where another ends waits for it.
Do I need expensive software to manage a Gantt chart?
No. A spreadsheet is enough for a small project. Dedicated tools add automatic arrows and updates, which helps only when there are many tasks.
Can a Gantt chart show me who is working on what?
Yes. Put the owner's name on each bar. It also shows overload: one person with three overlapping bars in the same week.

Sources: Wikipedia, articles "Gantt chart" and "Karol Adamiecki"

Last reviewed: 2026-09-24

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