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Pros and Cons of PERT and Gantt Charts

written by: Gary Picariello • edited by: Michele McDonough • updated: 6/13/2010

When it comes to project scheduling, both the PERT chart and the Gantt chart are common tools used by many project managers. But what are the pros and cons of each?

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    Weighing the Pros and Cons

    Like any management tool, the PERT (Project Evaluation Review Technique) and Gantt (named after Henry Gantt) charts are only as helpful as the user makes them. In the world of project management, the PERT and GANTT charts often get played up as THE premier “flow chart” for project success, and while that may be true to an extent, there are pros and cons to each one. The sooner you get a handle on what the PERT and Gantt charts have to offer the better off you’ll be.

    For starters, both charts help the manager plan and coordinate all the steps necessary for project completion – from schedule preparation to allotment of resources. Both the PERT and Gantt charts give you the benefit of monitoring task and goal completion. Likewise – and perhaps most important – both charts help managers plan all tasks that need to be completed in addition to providing a snapshot of areas that need improving.

    But is either the Gantt or PERT chart right for you and your project? Here are some tips to help you make your decision:

    Why you need the Gantt chart:

    • Gantt charts are more ideal for small projects than large.
    • The Gantt chart provides optimum opportunity to present each stage of your project. It has everything from listing goals to resource allotment.
    • The Gantt chart can be used in status reporting to show how much of the plan has been completed by displaying the progress of an activity. In the same or a parallel bar, or using color, many executives prefer this presentation format.

    Conversely, Gantt charts may toss a wrench in your operations:

    • Before the chart can even be drawn up, you need to have your project estimates worked out.
    • The Gantt chart doesn’t really allow for the correlation and/or dependency between jobs.
    • Start/stop dates per task are easier to plug in then are multiple start dates.
    • If you want to make changes to your schedule, you need to redraw the chart! Who has time for that? And you can’t map out multiple scheduling options within the same chart. However, when using a program like Microsoft Project, Gantt charts are updated dynamically as the project schedule changes.

    For more samples and information on how to construct a Gantt chart in various software applications, please see Gantt Chart Examples and Tutorials.

    PERT has the following advantages:

    A PERT chart explicitly defines and makes visible dependencies (precedence relationships) between the WBS elements. PERT encourages the identification of the project’s critical path. PERT encourages the identification of early and late start, and slack for each activity.

    On the other hand…

    When using a PERT chart, the relationship between the task at hand and the time allotted for said task may not be as immediately obvious -- as say -- with a Gantt chart. For this reason, above all, the PERT chart can be a real pain in the neck for someone who is not familiar with the PERT chart. PERT charts also tend to underestimate actual risks inherent to your project. Not a good thing when you’re juggling contract worth hundreds of thousands of dollars or more.

    There you have it: the good, the bad and the ugly of the Gantt and PERT charts. If used in tandem with the other tenets of project management you could find yourself on the fast-track to project completion. But if you think either chart is a panacea to cure your troubles you could be looking at a rocky road to success.