A Work Breakdown Structure decomposes total project scope into progressively smaller, manageable components. It is the most important planning document most PMs underuse.
- A WBS defines deliverables, not activities
- The 100% rule: include all deliverables and nothing outside scope
- A good WBS surfaces scope gaps before planning begins
Structure and decomposition
Level 1 is the project; Level 2 is major deliverable groupings; Levels 3+ are progressively smaller. Decompose to the level where you can estimate and track reliably.
Deliverables vs activities
A WBS element is a noun (deliverable), not a verb (activity). "Requirements document" is a WBS element; "write requirements" is a schedule activity.
The 100% rule
The WBS must include 100% of project scope and nothing more. This makes scope omissions visible before planning begins.
The WBS dictionary
Extends each element with a description, owner, acceptance criteria, and estimate, transforming the structure into a governance document.
Frequently asked questions
Complex projects benefit greatly; simple projects can use a work package list. The principle applies universally.
Decompose until you can reliably estimate, assign, and track each element.
Microsoft Project, Miro, or an indented Word/Excel document all work.
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