Work Breakdown Structure

Once the project manager and the project sponsor officially accept the scope-defining documents—the completed SOW, the project charter, the requirements documentation, and the scope statement—the project manager can start to think about how the actual work of the project will be completed. These input documents provide project managers with the information they need to engage the planning process group and the security they need to believe that the scope is firm and likely to change in only manageable ways.

Project managers rely on the work breakdown structure (WBS) technique to plan the actual work for the project. The primary process of this tool is decomposition, or the process of starting with high-level goals or deliverables and then working backward to break those large objectives up into smaller and smaller tasks. These tasks are usually arranged in a visual table with high-level objectives at the top cascading down to small tasks at the bottom. For complex projects, the project manager may elect to create a WBS dictionary, which briefly clarifies all the items that are contained in the WBS to make the document accessible for people who are not immediately involved on the project.

Major Milestones

Milestones are significant events in a project’s life cycle. They can indicate the completion of a certain group of tasks or the meeting of a certain requirement for a project. When the wedding planner worked to gather requirements with the couple getting married, they established that finalizing plans for the venue, the guests, the catering service, and the entertainment were four major milestones. These requirements become the high-level milestones in the WBS chart (the green level). When a project team completes a milestone, the project manager should report the progress to the project sponsor. The completion of major milestones may signal that other actions should occur as well, such as the handover of a major deliverable.


To discover how projects are broken down into milestones and then further broken down into smaller tasks, consider the project of planning a wedding. The WBS chart in the figure below does not include all of the deliverables and milestones for planning a wedding; it only highlights some of the tasks associated with catering.

Major Deliverables

Deliverables are products or results that are handed over from one person to another and that will be evaluated based on how closely they meet the specifications that were outlined during the initiating process group. Project managers move backward from the major milestones to determine what the necessary deliverables are. For example, the milestone met when the catering plan is complete requires a contract with the pastry chef. This contract represents a deliverable that the project manager (the wedding coordinator) will submit to the client (the couple getting married). The major catering deliverables in the wedding WBS are listed directly below the catering milestone.

Major Tasks

Once project managers identify the major deliverables for a project, they decompose the deliverables into smaller tasks. Each extra level of decomposition represents a more specific documentation of the project. These are the activities that the project team must complete in order to prepare the deliverable. In the figure above,  the purple boxes indicate major tasks. In order to sign a contract with the pastry chef, the wedding planner and the couple getting married first must finalize the cake design. This task is a step toward completing the pastry chef contract deliverable.

Lowest Level Tasks

Complex projects often feature yet another level of decomposition. The scope of major tasks is relative to the size and complexity of a project, but they characteristically require more than one step to be completed. For this reason, project managers sometimes break down the major tasks into one or more additional levels of subordinate tasks. Each extra level of decomposition represents more specific documentation of the project. The lowest level tasks are sometimes called work packages. Work packages can be accurately measured in terms of how many resources they will require. Project managers can develop accurate estimates of time and cost for meeting each major task, deliverable, and milestone by making these calculations for all of the relevant work packages.

The Proper Break Down of Tasks

As with any planning tool, a WBS is only useful if it is applied thoughtfully and purposefully. One decision project managers must make is how many levels to include in their task breakdown. Failing to include enough levels of decomposition can mean the project manager will not have a clear understanding of how much time and how much money each deliverable will require. Alternatively, providing too many levels of decomposition can be disorienting to project managers who must efficiently track and monitor the progress of projects.

Project managers often enlist the help of consultants and experts to ensure that their WBS tables are realistic and accurate. The process of creating a WBS table forces project managers to consider the project at a granular level—this new perspective of the project starts to reveal more accurate information about the future cost of project tasks. This breakdown also serves the project manager as a useful tool for monitoring and controlling project processes. The scope-defining documents directly inform the WBS: if all of the tasks described on the WBS are executed correctly, the end deliverables should, in theory, match the initial scope definition.

Major Subcomponents of a Work-Breakdown Structure (WBS)

The number of activities within a project varies for each project.  The level of detail with which the project manager wants to monitor and control the project impacts the number of activities.  A work-breakdown structure (WBS) details the activities in a project by dividing the project into major subcomponents.  The major subcomponents are broken down into more detailed components and so on.

WBS Presented

The work breakdown structure (WBS) can be presented in a number of formats:

  • numbered list
  • outline list
  • Gantt chart

Dependencies among tasks are not typically shown on a Gantt chart, but they can be inferred by the way the tasks are ordered. If the dependencies want to be viewed in a detail, a network diagram is the most effective format.

The next step in the project planning is to identify the time required and other resources for each activity.

Determining Effort and Duration

Once the work breakdown structure is completed with the activities and their sequence, it is time to assign effort and resources to calculate dates. The project manager doesn’t create the schedule in isolation; he or she needs to make sure that the schedule is created with input from the people who have the best information.

After the tasks and dependencies are correct, the project manager and his or her team can assign efforts and duration to tasks. Effort refers to the total amount of time (hours) that it will take to complete the activity. Duration refers to the total number of elapsed days the task will span. Duration and effort are related by the availability of resources—how much time a resource is able to work on the activity. For example, a task that will require 40 hours of effort is assigned to someone who can work on it 20 hours per week, or 4 hours per day. This task will have duration of 10 days (40 hours divided by 4 hours per day). If resource availability is greater, the duration can be shorter. This example is of an effort-driven task; the effort remains constant, and the duration and availability change. Tasks can also be duration-driven or resource-driven. Generally, the project manager will determine which overall approach works for his or her project, and then he or she will identify the exceptions.

There are no shortcuts to determining effort and duration—it must be done task by task for the entire project. Leveraging information from similar projects and their plans, as well as tapping the intellectual capital of the team, are techniques that can make this step less tedious.

It is very tempting to assign duration and an effort to each task to create a schedule that hits certain dates. However, that will result in a schedule that is resource-driven, which may not be applicable to your environment. In other words, you are creating a schedule that is not realistic from the very beginning.

Duration: The overall amount of time given to accomplish a task –usually measured in days.

Units: How much of their total available time a resource gives to a task – usually measured in percentage.

Work: The amount of time that it takes to do actually do the task –

Usually measured in hours.

Assigning People to Tasks

After the project manager has assigned an effort and/or duration to the tasks, it is time to assign resources to the tasks. The best place to start is not with the people but with the necessary skills. While this may not seem realistic, it is a critical step. The project manager needs to have a good understanding of the skills that are needed on the project to complete the work. Once that understanding exists, then the project manager can assign the tasks to specific people. Now the project manager is able to look at the skills available to the project and determine which skills are missing or underdeveloped. This now gives a sense of the risks the project faces due to skills gaps. The project manager is then able to create action plans that may have additional schedule or cost implications. For example, it may be possible to provide training to the team members, increase or decrease task efforts and/or durations, see if a “trade” can be made with another project, etc., or perhaps a customer has the missing skill set and can take a larger role on the project.

In the work breakdown structure, the project manager defines a list of all deliverables that the project requires. The key to developing a work breakdown structure is to have a strategic and logical thinker on the team. It does not have to be the project manager, but it does have to be someone on the team who can think broadly and specifically and who is good at organizing information.

The work breakdown structure is easily misunderstood. The most common mistake is including activities in the plan when all it requires are nouns. The goal is not to outline what people are doing but what team members are delivering. Thus, in the creation of an alumni magazine, work breakdown structure would likely proceed with the members of the group gathering together around a blackboard and itemizing the specific things they need to include. With one person leading and others listing deliverables, the meeting manager would write down and organize at the same time the different deliverables.


Lynda. (2011). What is a work breakdown structure? [Video]. Retrieved from the YouTube Web site:

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