Gantt Chart
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A Gantt chart is a type of
bar chart A bar chart or bar graph is a chart or graph that presents categorical data with rectangular bars with heights or lengths proportional to the values that they represent. The bars can be plotted vertically or horizontally. A vertical bar chart is ...
that illustrates a project schedule, named after its popularizer,
Henry Gantt Henry Laurence Gantt (; May 20, 1861 – November 23, 1919) was an American mechanical engineer and management consultant who is best known for his work in the development of scientific management. He created the Gantt chart in the 1910s. Gan ...
(1861–1919), who designed such a chart around the years 1910–1915. Modern Gantt charts also show the dependency relationships between activities and the current schedule status.


Definition

A Gantt chart is a type of bar chart that illustrates a project schedule. This chart lists the tasks to be performed on the vertical axis, and time intervals on the horizontal axis. The width of the horizontal bars in the graph shows the duration of each activity. Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a
project A project is any undertaking, carried out individually or collaboratively and possibly involving research or design, that is carefully planned to achieve a particular goal. An alternative view sees a project managerially as a sequence of even ...
. Terminal elements and summary elements constitute the
work breakdown structure A work-breakdown structure (WBS) in project management and systems engineering is a deliverable-oriented breakdown of a project into smaller components. A work breakdown structure is a key project deliverable that organizes the team's work into ...
of the project. Modern Gantt charts also show the dependency (i.e., precedence network) relationships between activities. Gantt charts can be used to show current schedule status using percent-complete shadings and a vertical "TODAY" line. Gantt charts are sometimes equated with bar charts. Gantt charts are usually created initially using an ''early start time approach'', where each task is scheduled to start immediately when its prerequisites are complete. This method maximizes the float time available for all tasks.


History

Although widely used in project planning in the present day, Gantt charts were considered revolutionary when introduced. The first known tool of this type was developed in 1896 by
Karol Adamiecki Karol Adamiecki ( Dąbrowa Górnicza, 18 March 1866 – 16 May 1933, Warsaw, Poland) was a Polish engineer, management researcher, economist, and professor. Life Karol Adamiecki was a prominent management researcher in Eastern and Central Eur ...
, who called it a ''harmonogram''. Adamiecki, however, published his chart only in Russian and Polish which limited both its adoption and recognition of his authorship. In 1912, published what could be considered Gantt charts while discussing a construction project. Charts of the type published by Schürch appear to have been in common use in Germany at the time; however, the prior development leading to Schürch's work is unclear. Unlike later Gantt charts, Schürch's charts did not display interdependencies, leaving them to be inferred by the reader. These were also static representations of a planned schedule. The chart is named after
Henry Gantt Henry Laurence Gantt (; May 20, 1861 – November 23, 1919) was an American mechanical engineer and management consultant who is best known for his work in the development of scientific management. He created the Gantt chart in the 1910s. Gan ...
(1861–1919), who designed his chart around the years 1910–1915. Gantt originally created his tool for systematic, routine operations. He designed this visualization tool to more easily measure
productivity Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production proces ...
levels of
employees Employment is a relationship between two parties regulating the provision of paid labour services. Usually based on a contract, one party, the employer, which might be a corporation, a not-for-profit organization, a co-operative, or any othe ...
and gauge which employees were under- or over-performing. Gantt also frequently included
graphics Graphics () are visual images or designs on some surface, such as a wall, canvas, screen, paper, or stone, to inform, illustrate, or entertain. In contemporary usage, it includes a pictorial representation of data, as in design and manufacture ...
and other visual indicators in his charts to track performance. One of the first major applications of Gantt charts was by the United States during
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, at the instigation of General William Crozier. The earliest Gantt charts were drawn on paper and therefore had to be redrawn entirely in order to adjust to schedule changes. For many years, project managers used pieces of paper or blocks for Gantt chart bars so they could be adjusted as needed. Gantt's collaborator
Walter Polakov Walter Nicholas Polakov (July 18, 1879 – December 20, 1948 ) was a Russian mechanical engineer, consulting engineer, and pioneer of scientific management. Biography Early years Walter Polakov was born in Luga, Russia, and attended High Sc ...
introduced Gantt charts to the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
in 1929 when he was working for the Supreme Soviet of the National Economy. They were used in developing the
First Five Year Plan The first five-year plan (russian: I пятилетний план, ) of the Union of Soviet Socialist Republics (USSR) was a list of economic goals, created by Communist Party General Secretary Joseph Stalin, based on his policy of socialism in ...
, supplying Russian translations to explain their use.Kelly, D. J. (2004)
Marxist Manager Amidst the Progressives: Walter N. Polakov and the Taylor Society
, ''Journal of Industrial History'', 6(2), November 2004, 61-75
In the 1980s, personal computers allowed widespread creation of complex and elaborate Gantt charts. The first desktop applications were intended mainly for project managers and project schedulers. With the advent of the Internet and increased collaboration over networks at the end of the 1990s, Gantt charts became a common feature of web-based applications, including collaborative groupware. By 2012, almost all Gantt charts were made by software which can easily adjust to schedule changes. In 1999, Gantt charts were identified as "one of the most widely used management tools for project scheduling and control".


Example

In the following tables there are seven tasks, labeled ''a'' through ''g''. Some tasks can be done concurrently (''a'' and ''b'') while others cannot be done until their predecessor task is complete (''c'' and ''d'' cannot begin until ''a'' is complete). Additionally, 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 estimated using the beta probability distribution for the time estimates, using the formula (''O'' + 4''M'' + ''P'') ÷ 6. Once this step is complete, one can draw a Gantt chart or a network diagram.


Progress Gantt charts

In a progress Gantt chart, tasks are shaded in proportion to the degree of their completion: a task that is 60% complete would be 60% shaded, starting from the left. A vertical line is drawn at the time index when the progress Gantt chart is created, and this line can then be compared with shaded tasks. If everything is on schedule, all task portions left of the line will be shaded, and all task portions right of the line will not be shaded. This provides a visual representation of how the project and its tasks are ahead or behind schedule.


Linked Gantt charts

Linked Gantt charts contain lines indicating the dependencies between tasks. However, linked Gantt charts quickly become cluttered in all but the simplest cases.
Critical path network diagram The program evaluation and review technique (PERT) is a statistical tool used in project management, which was designed to analyze and represent the tasks involved in completing a given project. First developed by the United States Navy in 1 ...
s are superior to visually communicate the relationships between tasks. Nevertheless, Gantt charts are often preferred over network diagrams because Gantt charts are easily interpreted without training, whereas critical path diagrams require training to interpret. Gantt chart software typically provides mechanisms to link task dependencies, although this data may or may not be visually represented. Gantt charts and network diagrams are often used for the same project, both being generated from the same data by a software application.


See also

* Critical path method *
Event chain methodology Event chain methodology is a network analysis technique that is focused on identifying and managing events and relationship between them (event chains) that affect project schedules. It is an uncertainty modeling schedule technique. Event chain m ...
*
Float (project management) In project management, float or slack is the amount of time that a task in a project network can be delayed without causing a delay to: * subsequent tasks ("''free float''") * project completion date ("''total float''"). ''Total float'' is assoc ...
*
List of project management software The following is a comparison of project management software. General information Features Monetary features See also * Kanban (development) * Project management software * Project planning * Comparison of scrum software * Compari ...
, which includes specific Gantt chart software. *
Program evaluation and review technique The program evaluation and review technique (PERT) is a statistical tool used in project management, which was designed to analyze and represent the tasks involved in completing a given project. First developed by the United States Navy in ...
(PERT) *
Event chain diagram Event chain diagrams are visualizations that show the relationships between events and tasks and how the events affect each other. Event chain diagrams are introduced as a part of event chain methodology. Event chain methodology is an uncertainty ...


Citations


References

* * * ; republished as * * * * * * () * * Adapted from Adapted from an even earlier 2006 presentation. *


Further reading

* * * * * * * * * *


External links

{{Wiktionary
Long-running discussion
regarding limitations of the Gantt chart format, and alternatives, on
Edward Tufte Edward Rolf Tufte (; born March 14, 1942), sometimes known as "ET",. is an American statistician and professor emeritus of political science, statistics, and computer science at Yale University. He is noted for his writings on information design ...
's website Diagrams Planning Project management techniques Technical drawing Schedule (project management) Charts