Gantt Charts

A Gantt chart is a type of bar chart, developed by Henry Gantt, that illustrates a project schedule. Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project. Terminal elements and summary elements comprise the work breakdown structure of the project. Gantt charts have become a common technique for representing the phases and activities of a project work breakdown structure (WBS), so they can be understood by a wide audience all over the world.

A work breakdown structure (WBS), in project management and systems engineering, is a deliverable oriented decomposition of a project into smaller components. It defines and groups a project’s discrete work elements in a way that helps organize and define the total work scope of the project.

To make a Gantt Chart:

  1. Identify a project with very specific outcomes.
  2. Divide into tasks that will need to be completed in order to finish the project. Some tasks can be done concurrently while others cannot be done until their predecessor task is complete.
  3. Estimate how long it’s going to take: each task has three time estimates: the optimistic time estimate (O), the most likely or normal time estimate (M), and the pessimistic time estimate (P). The expected time (TE) is computed using the formula (O + 4M + P) ÷ 6.
  4. Chart individual tasks by time.

Work breakdown schedule design principles:

  • 100% rule: the WBS contains 100% of the work included in the project’s scope; that is, everything required to complete the project.
    • Everything included within the WBS must add up to 100% of the work — it cannot include more (or less) than the entirety of the project
  • Mutually exclusive elements: there cannot be any overlap between different elements of the WBS. This could result in duplicated work or other problematic ambiguities
  • Plan outcomes, not actions: elements should be defined by their intended outcome, not the action it will take to achieve that outcome. This refusal to be prescriptive of methods allows for greater ingenuity and creative thinking.
  • Level of detail: there are a few rules of thumb used to determine the appropriate duration of activity necessary to one objective
    • “80 hour rule” – no single activity or group of activities necessary to one deliverable should take more than 80 hours
    • No activity or series of activities should be longer than a single reporting period. If reporting monthly, than nothing should take more than a month.
    • “Apply common sense” is a good rule too



WiP1 Notes. (March 2012)

O’Donnell, Jonathan. “How to make a simple Gantt ChartThe Research Whisperer. 13 September 2011

Wikipedia, “Gantt Chart“, “Work Breakdown Structure”

2 Responses to “Gantt Charts”
  1. dem says:

    So I know during the first WIP, I was the only one who seemed to think that Gantt charts were the bee’s knees. I still say, I want a Gantt chart for my life.

    But seriously, I do wonder whether this, even more than the generic flowchart, is what we want to set up for the running of the show itself — not the creation phase, but the, “we can’t go on to the next scene until so and so says such and such and the thingamajig is moved stage right” phase?

    I did a bunch of looking around at software options for Gantt charts, and one of most highly reviewed is also online, collaboration-ready, and free 🙂 Not to mention iPad-friendly! —

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  1. […] Gantt, an associate of Taylor’s, developed the Gantt chart, a bar graph that measures planned and completed work along each stage of production. Based on time […]

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