What is a Gantt Chart?
Is Gantt Chart same as a Scheduling Bar Chart?
What is a Time Scaled Logic Diagram? Is it same as Gantt chart?
What is a Time Scaled Network Diagram? How is it different from Gantt Chart?
Project Schedule can be represented in many ways. In one of my previous articles, on Project Schedule Network Diagrams, I outlined 4 ways for drawing Project Schedule. I have written this article to describe Scheduling Bar Chart. Scheduling Bar Chart is simply called Bar Chart. Bar chart is one of the most popular ways to pictorially represent Project Schedule. The other 3 ways to draw Project Schedule are:
- Project Schedule Network Diagrams
- Milestone Charts
- Project Calendars
So, what is a Gantt Chart?
Bar Chart is popularly known as Gantt Chart. The name is attributed to Mr. Henry Gantt who extensively used them in his work. Some Project Managers believe that he was the creator of Bar chart and hence the name. While others believe that Bar Charts were used by Planners even before Mr. Henry Gantt. History of Bar Charts is an interesting topic but I will leave it for another day. In this article I will use “Bar Chart” to mean “Gantt Chart” for those who are more familiar with the latter term.
What is a Bar Chart?
A Bart Chart is a 2-dimensional chart. Schedule Activities or WBS Components are represented as Horizontal bars in a Bar Chart.
- Vertical Axis is used for listing Schedule Activities or WBS Components. Usually left side is used for listing.
- Horizontal Axis is used as a time scale. It shows Activity Start & Finish dates.
- The length of bar represents activity duration. The duration can be shown in any time unit e.g. hours, days, weeks, months etc.
- Different colored bars are used to show finished and unfinished work. Usually finished portion of an activity is shown in dark color. Usually unfinished portion of an activity is shown in White or light color.
- A summary Activity is also shown as a Bar. Usually, Summary Bars have different color and/or shape than regular Bars.
- A milestone is generally shown as small rhombus.
You can also look at Max Wideman’s Glossary for some other definitions of Bar Chart.
Example of a Bar Chart
What is a Time Scaled Logic Diagram?
A Time Scaled Logic Diagram is a form of Bar Chart in which Project Dependencies are shown by using arrows. Two related Activities are joined by a unidirectional Arrow. Arrow Tail represents the Predecessor. Arrow Head represents the Successor. These diagrams are also called Time Scaled Network Diagrams. These Diagrams are a cross between traditional Bar Charts and Network Diagrams.
All Bar Charts are popularly known as Gantt Charts. A Time Scaled Logic Diagram can be used to draw 4 types of logical relationships:
Project Dependencies – Definition, Purpose & Example
Different Types Project Dependencies
8 thoughts on “What is a Gantt Chart?”
I also like to show resources on my Gantt/Bar charts. You can make the name of the resource display at the end of the bar (at least you can in the software I use). This is useful but if you’ve got more than one person working on a task it can get messy.
Nice stuff. I will make sure to use the charts in my next project.
Hi, it’s a great website there. Thanks for this info
Elizabeth, you can use Resource initials instead of full resource names. This will be helpful only if team size is small and if your scheduling s/w support initials. MSP supports resource initials.
Gantt Charts should be supported by mathematical analysis to ensure that they reflect a doable schedule.
I also think that summary Gantt Charts are best and a good tool for reporting status to management.
Thanks Bill. I agree. Gantt chart is an excellent tool for presentation & reporting purposes.
Excellent article. Very different from what I have read so far. Many thanks.
Saying all bar charts are Gantt charts is like saying all vehicles are Porsche 911s.
“Bar Chart” describes many types of graphs. When you simply say “bar chart” (without a modifier such as Gantt), it means that all bars begin at the X-axis for vertical bars or at the Y-axis for horizontal bars, and it shows only the relative sizes of measurements.
Time-Scaled Logic Diagrams (TSLDs) and Gantt Charts are two specific types of bar charts. Both show precedence relationships. Gantt charts are accompanied by a summary table on the left and show one activity per line in staircase fashion. TSLDs lack the tables and therefore allow you to view related activities in a single row, thus compressing the view of the schedule. For example, activities involving Milling Machine #3 or the Security Engineer might align horizontally.