Reading time: about 7 min PERT charts: Utilized before a project begins to plan and determine the duration of each task Gantt charts: Used while a project is happening to break projects into smaller tasks and highlight scheduling constraints Only 29% of projects are completed on time. And it’s no surprise why. With every project involving hundreds of moving parts, that’s a lot of information and deadlines to plan and track—leaving many managers struggling to stay on top of things. Yet, being able to clearly scope out your projects is critical to managing resources and ensuring projects are delivered on time and on budget. That’s where project management tools like PERT charts and Gantt charts can help. PERT charts and Gantt charts help teams visualize, plan, and manage complex projects This post outlines the differences between PERT and Gantt charts including when it's appropriate to use each chart and how you can make your own. What is a PERT chart?PERT stands for Program Evaluation and Review Technique. A PERT chart illustrates a project as a network diagram—visualizing the logical and sequential relationship between project tasks. The U.S. Navy created this tool in the 1950s to simplify planning and scheduling complex projects as they developed the Polaris missile (and time was of the essence—this was during the Cold War, after all). Project managers use PERT charts to gauge the minimum time necessary to complete the project, analyze task connections, and assess project risk. PERT is most useful in large-scale projects where time is the major factor rather than cost as the technique provides estimates based on optimistic, pessimistic, and expected timelines. PERT charts make it easy to visualize and organize complex projects illustrating the dependencies between each step in the project. Click to modify this PERT chart example
PERT charts are best utilized by project managers at the beginning of a project to ensure that it is accurately scoped. By averaging three timeline estimates (optimistic, pessimistic, and most likely) the PERT approach factors in uncertainties to predict realistic deadlines.
Keep in mind: PERT charts are about big-picture planning. While they can be used during the project's implementation to track progress, PERT charts are not flexible enough for teams to adapt them to small changes when team members are confronted with roadblocks. How to draw a PERT chartYou can design your PERT chart in a few different ways. The traditional PERT chart (also known as an activity-on-arrow diagram) contains two main elements:
Follow these steps to put your PERT chart together:
Once you draw your PERT chart, you'll want to use that information to determine a realistic timeframe for your project. This process is called the critical path method. The critical path is the longest sequence of tasks that need to be done in order to finish the project. If any of these critical tasks are delayed, the entire project will be set back. Find the longest path based on the time estimations you have entered. Remember that you’re not looking for the path with the most activities—you’re looking for the path with the activities that will take the longest. Add together the time it takes for each activity together and you’ll know how long the entire project should take. Now refer to your PERT chart to ensure that you finish your project by the deadline or to adjust the times as circumstances change. See a more detailed tutorial on how to create and use PERT charts for project management. Learn more
Created by Henry Gantt during WWI, Gantt charts visualize a project’s schedule from start to finish. Similar to a PERT chart, Gantt charts display tasks over time to ensure the project is completed on time. Project managers use Gantt charts to identify task dependencies, increase efficiencies, and improve time management. Gantt charts make it simple to break down projects into manageable steps that can adjust to the project as needed. Click to edit and share this Gantt chart template
Gantt charts are most useful to project managers during the project to make sure that each task is accomplished. Use Gantt charts to keep the project on track, communicate expectations and critical deadlines, and identify potential bottlenecks, resource overloads, or delays. Keep in mind: While Gantt charts are valuable management tools, they also require a lot of upfront work and an accurate scope to be effective. Find out more about using Gantt charts for project management. Learn more
Gantt charts are visually similar to a bar graph. Tasks are displayed vertically, and the timeline runs horizontally along the top of the chart. Each task is represented by a horizontal block and the length of the block indicates how long a task will take. Use the following steps to start your own Gantt chart.
Many people who ask “What is a PERT chart?” will immediately follow up with a second question: “How is it different from a Gantt chart?” Both are visual tools for project management, but you should consider some key differences between Gantt charts and PERT charts before you decide which will work better for your project. Like PERT charts, Gantt charts break projects into smaller tasks and highlight scheduling constraints. However, project managers use Gantt charts while a project is happening—they schedule tasks by date and show how much work has been completed. Every activity is represented with a bar that stretches from the start date to the end date of that activity. Use a Gantt chart if you need to:
PERT charts are generally used before a project begins to plan and determine the duration of each task—so they don’t have to show the actual dates of your project. They also do a better job of showing whether certain tasks need to be completed in order or whether they can be completed simultaneously. Use a PERT chart if you need to:
Both PERT charts and Gantt charts simplify the project management process to increase efficiencies and see the entire project. Whether you decide to use a PERT chart to plan your project or a Gantt chart to track and manage progress, consider using both strategically to organize and implement your project. Start your projects right and keep them moving forward—sign up for a free Lucidchart account. Sign up free |