What is a work breakdown structure (WBS)?

Work breakdown structure is a method in project management for deconstructing complex projects into manageable and trackable tasks.

Also referred to as WBS, the goal of work breakdown structure is to make large, multi-step projects easier to manage. It does this by breaking the projects down into smaller tasks and processes. These individual tasks can then be addressed and completed simultaneously by different teams or team members, allowing for a faster, more efficient project turnaround.

A work breakdown structure takes the form of a detailed diagram, identifying and breaking down the deliverables and associated activities necessary for completion. The primary, final deliverable is situated at the top of the diagram, with sub tasks organised below it. WBS is often used in conjunction with a Gantt chart and IT project management software to improve the planning and execution of otherwise-daunting projects.

Work breakdown structure is generally divided into three distinct types: deliverable-based WBS, phase-based WBS and responsibility-based WBS.


This approach identifies the connections between the project’s scope and its deliverables. It decomposes the scope into smaller, more manageable deliverables—usually something specific that must be produced, supplied, or obtained by executing project tasks to satisfy project requirements.


The phase-based WBS breaks the project down into five distinct stages: initiation, planning, execution, control and close. Within each of these stages are unique deliverables.


A responsibility-based breakdown defines the structure of the project based on the teams, individuals and organisation units that will be working on the project. While the second level of the structure will identify who is responsible to complete the tasks, the subsequent levels follow a similar format to other WBS types, identifying deliverables that must be completed to move the overall project forward.

Less-common WBS types

Additionally, there are several less-common approaches to WBS. These include the following:

  • Verb-oriented
    Uses actions to define deliverables.
  • Noun-oriented
    Uses components to define deliverables.
  • Time-phased
    Breaks projects into separate time-periods or phases.

As previously stated, the WBS takes the form of a diagram with the final deliverable at the top and all sub items arranged below it. These sub items are usually divided into four distinct levels or tiers. This allows teams to more easily visualise the steps needed to complete the project. The four levels of a work breakdown structure are top level, controls account, work packages and activities.


At the top of the diagram sits the final deliverable. The top level can also be the project title.

Controls account

The second level consists of the different main project phases. These are the secondary deliverables that must be completed to ensure a successful project.

Work packages

The work packages sit under the controls-account level, identifying the necessary tasks that go into the secondary deliverables.


This principal also addresses risk and uncertainty using milestones. The whole The final level consists of the activities that facilitate the work packages.

Essentially, every level is supported by the level that follows it. In a traditional breakdown diagram, this results in a branching chart that flows downwards from the final deliverable, taking into account all of the essential tasks, activities and deliverables that need to be performed to complete the project.

Although the aforementioned approach may be the most widely used of WBS diagrams, it is not the only option. There are several different variations of the classic WBS diagram, including the following:

Tree diagram

As described above, the tree-diagram WBS represents the workflow as branching elements leading down from the primary project deliverable. Each level is made up of tasks that support the level above it. This is the most-common approach to WBS diagramming.


Although not as detailed as some other options, the WBS list may be the simplest and easiest option for organisations who just need a quick outline of deliverables and subtasks. It consists of little more than a list identifying and breaking down important tasks.


All of the information presented in the tree diagram can be just as easily represented and organised using a spreadsheet. The spreadsheet approach uses columns and rows to detail the various levels, tasks and deliverables. Spreadsheets are often dynamic, shared documents that can be updated in real time to account for any changes to the project.

Gantt chart

Using project management software, organisations can create detailed Gantt charts capable of linking relevant information, applying discrepancies, setting milestones and more. These charts are similar to spreadsheets in that they allow for dynamic updating, but they also function as a timeline for the project itself.

Regardless of the format the diagram takes, creating a work breakdown structure consists of five steps.

Define objectives

Determine the scope and objectives of the project, and who will be involved in it. Describe the overall project and what it is designed to accomplish.
Graphic of how to create a work breakdown structure

Break down phases

Determine what steps, tasks, activities and deliverables will guide the project towards completion. Organise these elements into a series of phases.

Identify deliverables

Identify the specific deliverables associated with each phase. List them out, and identify the conditions by which each deliverable will be successfully completed.

Break down deliverables

Further break down the deliverables from the previous step into their own constituent tasks and subtasks. List these tasks sequentially.

Assign tasks

Once all relevant tasks have been identified and organised according to phase, assign them to the teams and individuals who will be responsible for delivering on them. Authorise the teams to act on the project, and provide any resources and tools they might need.

WBS exists to make complex, multi-step projects more manageable. But often, simply trying to break down these projects can itself be a complex and difficult process. WBS software is a type of tool designed to streamline and automate various aspects of WBS.

A well-designed WBS should use visualisation techniques to clearly describe the various elements that make up a project, and detail how those elements support one another in achieving a desired goal. With that in mind, here are several best practices to create a work breakdown structure.

Include 100% of the work

The WBS shouldn’t omit any tasks, no matter how small. At each level, the deliverable should consist of the total sum of the work detailed in the level below it.

Focus on coherency

The point of WBS is to make complex projects easy to understand. The WBS should be easy for all participants to understand without need for detailed explanation.

Don’t duplicate tasks

Don’t bother making separate tasks for work that is already addressed in a different task. Keep tasks mutually exclusive.

Make tasks manageable

Tasks should be broken down far enough that they can be completed by an individual within a reasonable amount of time.

Use no more than five levels

Although it’s important to account for all of the tasks that go into a project, don’t go too deep. Creating too many layers of subtasks can make the project feel confusing and overwhelming. Five levels or fewer should be enough to simplify even the most-complex projects.

Ensure measurability

Individual tasks should be trackable, consisting of concrete deliverables and supported by milestones and completion dates. This allows for measurability, and makes it possible to improve WBS effectiveness.

Be willing to adapt

The WBS should provide an accurate representation of the scope of the project. If the project itself changes, or if it becomes apparent that the WBS is lacking in any way, managers need to be willing to revise the structure at any given level.

ServiceNow IT business management (ITBM) gives organisations the power to easily plan, prioritise and track tasks associated with business objectives. Built on the Now Platform, ITBM incorporates real-time updates, offers a single data model, is fully mobile compatible, and supports PPM, APM and Agile solutions. In other words, ITBM is an essential resource for creating effective work breakdown structures.

Learn more about WBS in ITBM, and turn even your most complex projects into manageable, streamlined processes.

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