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Gantt Chart

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A Gantt chart is a visual project management tool first developed and used by Henry Gantt during World War I. Gantt charts, also known as bar charts, time lines, or milestone charts are one of the most popular and useable ways to present project information.

The parts of a Gantt chart.

A Gantt chart lists tasks or phases of a project from top to bottom and has time running from left to right. Each task has a start date and duration (or end date). Planned tasks are usually drawn as open bars, which are filled in as the work is done. Alternatively separate filled in bars can be drawn below the open bars to more clearly show how the tasks are proceeding in relation to their planned schedule. Additionally, a Gantt chart may show the resources required for a particular task as well as project milestones and/or task interdependencies.

Advantages and disadvantages.

Some of the advantages of Gantt charts are that they are simple and visual. It is relatively easy to explain a Gantt chart even to those who have never seen one before. Because of this simplicity, Gantt charts are used in both large and small projects. However, large or complex projects may demand more sophisticated methods in addition to Gantt charts. Another problem with Gantt charts is that it may be difficult to determine how a complex series of tasks interrelate. It does not show the delay on some elements. It does not give a clear indication of interdependence of the various activities. It does not gives the planner what activities must be completed on schedule to ensure the project completed as planned. Also does not gives the planner how much an activity may be delay without influencing the start of another activities.

Other project management systems.

In response to the limitations of Gantt charts, two other scheduling control systems were developed in the 1950’s. These systems are known as Critical Path Methods (CPM) and Program Evaluation and Review Techniques (PERT). Both provide better control and scheduling for complex projects by more clearly showing the relationships between tasks. CPM and PERT are sometimes combined into what are known as PERT/CPM networks. Even when PERT and/or CPM are employed, Gantt charts are still used to define overall scheduling priorities and to show project status.

How to create a Gantt chart.

Creation of a Gantt chart can be broken down into several steps. First identify the tasks or phases of a project. Although this may be done at a number of levels of detail, keep in mind that tasks should be characterized by specialization, dependence on prior task completion, and necessity for subsequent tasks. In developing a list of tasks for a complex project use a top down approach starting with the major phases or parts of the work and then moving on to smaller subtasks. Second, plan the start dates for each task. Some tasks may be able to be executed concurrently while others will depend on the completion of prior tasks and therefore must be executed sequentially.

Many tasks may vie for resources and for that reason may not be able to run concurrently. Third, estimate the duration of each task again consider the resources assigned to the task. If one person works on three tasks concurrently the time required to complete any one of the tasks will be longer that if the tasks were run consecutively but the total time to complete the three tasks may be greater, the same, or less. Fourth create the Gantt chart. Gantt charts can be drawn by hand, in a drawing program or with one of the may project management software packages available.

Activity on arrow & Activity on node


Functional management is a term used to describe the traditional day-to-day management role. Project management is about managing the unique tasks termed as projects. Projects are often described as being short-term tasks aimed at bringing about change. The essential features of a project will include (a) A specified objective, (b) Target start and finish dates, (c) Some form of funding/allocated resource.

Examples of Projects.

The associated research and development of a new product.

The initial launch of a new product.

Major business purchases such as new factories, machines, computers, etc.

Why have project planning?

To make people within the organisation aware that a change is about to happen

To reduce uncertainty in the implementation stage.

To develop a method for monitoring the change.

Critical Path Method (CPM).

The critical path method was first developed at Dupont during the 1950’s. CPM analysis consists of using a lot of diagrams to look at the activity, time needed and result. We advise you to read a CPM based book in conjunction with reading this section to see how the diagrams develop. We shall now briefly discuss CPM logic.

There are 2 basic areas of CPM:

A. Activity on arrow.

B. Activity on node.

A. Activity on arrow. Basically the diagrams are constructed using arrows. An activity is used describe a task that needs to be completed or is waiting to be completed. An event is the start/completion of a activity/series of activities.

Normal activities are show as straight lines with arrows attached. Dummy activities are described as being something that needs to occur but which does not take up any resources, these are shown as:

The general convention of the diagrams (a) time goes from the left to right, (b) the arrow length has no meaning (c) the logic is that as one activity emerges from another activity it gets a higher number.

A. Activity on node. Essentially the same as the Activity on Arrow method except instead of using circles in the diagrams, we use nodes (rectangles). The essential problem with the Activity on Node method is that there exist several standards of use.

The activity in the Activity on Node method is the same as the Activity on Arrow method. An activity can be described as the work entailed in a project; the nodes are numbered from left to right. The nodes contain an activity, a description and the duration time. Dependencies are shown as the relationships between activities.

CPM is a good method of analyzing tasks for a project, but before using the models please read further texts on the matter.


If your business is about to embark on the implementation of a major strategy/investment program, it is vital that a team be selected adequately to manage the project. The team needs to consist of the most suitable people required on the project. The team needs to be nurtured by senior management and allowed to make decisions that are the may not seem suitable to senior management but are for the good of the business. CPM is a good method of analyzing tasks, there are however several methods for analyzing both tasks and major capital expenditure, be sure to read further books on the subject.

Earliest and latest event time.

The early event time for a given node is defined as the earliest time an activity beginning from this node can start. The early event times for different activities form what is called the forward pass, which is the first step in establishing the critical path for the network. As agreed, the network flows from left to right. The forward pass keeps on adding the durations of the different activities until the end of the network (last activity) is reached, hence determining the earliest completion date for the whole network. We always assume that the project will start at the beginning of day zero (0), which would be the early event time (early start) for the first node (and all the activities starting from this node). The early event time for the immediate successor is equal to the early event time of the predecessor + the duration of that predecessor, as shown in the figure below.

When more than one activity enter a node (2 or more predecessors), the finish time of the later one is considered as the early start time for the successor.

The late event time (late start or late finish) is calculated through a reverse process to the forward pass, which is called the backward pass. Anything added in the forward pass will be subtracted in the backward pass. The late finish time is defined as the latest time an activity entering the node can finish, whereas the late start time is defined as the latest time an activity leaving the node can start.

It is to be noticed that the durations (which were added during the forward pass) were subtracted in the backward pass. The process of comparing the forward pass to the backward pass will result in determining the critical activities, therefore the critical path. For an activity to be critical, the early event times have to be equal to the late event times (i.e. the early start = the late start, and the early finish = the late finish). Such an activity or activities are called critical since any delay in any of them will cause a delay to the whole project. The difference between the late start (LS) and the early start (ES), or between the late finish (LF) and the early finish (EF) is called to total float. Total float (TF) = LS – ES = LF – EF = LF- (ES + duration) The physical meaning of the total float is the amount of time by which an activity can be delayed without causing a delay to the whole project. By definition, the critical activities will have zero total float, as their ES = LS and EF = LF.

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