​Depending on industry and business, project management can be a complex undertaking that requires a framework to accommodate many moving pieces. One commonly used technique, work breakdown structure (WBS), is situated within the planning portion of the project life cycle.

It seeks to break larger projects into smaller, more manageable segments and deliverables. The overarching project objective is placed at the top with a tree-like hierarchy, and its dependent components are arranged below. At the bottom of the chart, such dependencies are broken down and defined as specific tasks.

The WBS concept was initially developed at US agencies such as NASA and the Department of Defense (DOD) and utilized in shepherding the Polaris missile program and other ambitious projects to completion.

One foundation of WBS is the 100 percent rule, a requirement that every element needed to achieve the completed project (defined at the top of the tree) be accounted for. Additionally, adding up all tasks within each level within the hierarchy should account for 100 percent of the work that needs to be completed, all described at that level.

The tasks presented should encompass critical path items or project elements that must be undertaken in order. It also should include elements that can be delayed or accomplished in parallel to other work, with minimal impact on budget or timeline. To avoid duplication and unnecessary redundancies, each piece of work within the tree should be unique and not identical to any other.

Workers engaged in siloed work within larger projects benefit from a WBS visual representation guiding them, as they know exactly the desired result and where their efforts fit within the larger picture. In addition, breaking down a complex project into small components helps create greater efficiencies, as achievable milestones are laid out on the way to completion. Tracking progress is also simplified, as it's often possible to define just what percentage of work remains to be accomplished.

An example of a WBS tree structure is one in which a house's construction sits at the top of the hierarchy. This is broken down into three levels: 1. internal, 2. foundation, and 3. external, each arranged parallel to the others, with lower levels extending downward. The 2. foundation level has two major subcategories: 2.1 excavation and 2.2 steel erection. Within 2.1 excavation, another sub-hierarchy of defined tasks exists: 2.1.1 pour concrete and 2.1.2 cure and strip forms. Within the 2.2 steel erection levels, the subtasks are different: 2.2.1 steel columns, 2.2.2 beams, and 2.2.3 joists. Naturally, this structure or arranging tasks can be expanded infinitely, depending on the project's complexity.

Another example of a WBS tree guides the development of a new mobile app. Within the parent objective of "launching a new app," there are three primary level-two dependencies: design a user interface, create a database, and develop back-end logic, each broken down into further tasks and subtasks.

In today's technologically informed planning environment, project management software is often employed in laying out and executing work breakdown structures. WBS often uses Gantt charts (horizontal bar charts) to define hierarchies, enabling the accurate scheduling of work needed to execute specific project elements. As each task progresses, results are automatically collated as real-time progress is defined and measured. This culminates in projects that reach completion with peak efficiency, within the deadline, and with the minimum expenditure of time and money.