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2.2.1.1

Concept · under Integrated planning, delivery approach and scope

The work breakdown structure on the PMP® exam

A work breakdown structure (WBS) divides the total project scope into deliverables, then into smaller pieces down to work packages, the level where cost and duration are estimated and the work is managed. It lists what the project produces; people and tasks are recorded elsewhere. With the scope statement and the WBS dictionary, it makes up the scope baseline.

Exam
PMP
Domain
Process
Domain weight
41%
Packages
9
Updated
Oct 13, 2026

01A WBS, numbered the way this binder is

Example: an office relocation decomposed to work packages

CodeElementLevel
1Office relocationProject
1.1New site readyDeliverable
1.1.1Floor plan approvedWork package
1.1.2Network cabling installedWork package
1.1.3Furniture in placeWork package
1.2Staff movedDeliverable
1.2.1Move schedule agreedWork package
1.2.2Equipment packed and transportedWork package
1.3Old site handed backDeliverable
1.3.1Lease exit inspection passedWork package
1.4Project managementDeliverable
1.4.1Status reports issuedWork package

Every element names a result you could inspect. Project management gets a branch of its own because it is work the project performs, and the 100% rule counts it.

02The 100% rule and how far to break things down

The WBS contains all of the project's work and nothing outside it. Each parent equals the sum of its children, so nothing is missing at any level and nothing is counted twice. Work that is not in the WBS is out of scope, which makes the WBS the reference point whenever someone proposes a change through integrated change control. Building it is part of scope planning, covered in integrated planning, delivery approach and scope.

Work packages and control accounts

Decompose until a piece can be estimated, given one owner and checked as done. Above the work packages, a control account is a management point where scope, budget and actual cost are compared for earned value; one control account can hold several work packages. Scheduling tools that label their task outline “WBS” blur a line worth keeping sharp: the WBS stops at work packages named as outcomes, and verbs like “pull cable” are activities in the schedule.

Resources are estimated against work packages too, which is where the resource side of planning starts: resources, procurement and contracts.

03Four breakdown structures with similar initials

WBS, OBS and the two kinds of RBS

PointWBSOBSResource RBSRisk RBS
Breaks downProject scope, into deliverablesThe performing organization, into unitsResources, by category and typeSources of risk, by category
Lowest levelWork packageTeam or roleA specific skill, machine or materialA specific risk source
Used forScope baseline, estimates, control accountsShowing which unit owns which work packagesPlanning and acquiring resourcesIdentifying risks systematically

Resource and risk breakdown structures are both abbreviated RBS. Read the stem for what is being broken down before you match the acronym.

04What the WBS dictionary adds

The chart carries names and codes. The WBS dictionary carries the detail behind each element: a description of the work, the responsible organization, assumptions and constraints, milestones, a cost estimate, quality requirements, acceptance criteria and technical references.

Think of it as the spec sheet that turns “1.1.2 Network cabling installed” into something a team can price, build and hand over.

05Break it down

The set leans on structure: what a WBS holds, how deep it goes, and which breakdown is which.

Work packages 9

  1. WP 01Two deliverables share overlapping components in a draft WBS. Which restructuring enforces the 100% rule without double-counting?

    Debrief answer to open the notes

    1. AMoving shared elements outside the WBS breaks the 100% rule, because the WBS must contain all project work.
    2. BCorrect: placing the shared elements under one parent includes them exactly once, so all work is covered without double-counting.
    3. CDuplicating elements under both parents counts the same work twice and violates the 100% rule.
    4. DOmitting shared elements leaves work out of the WBS, which also breaks the 100% rule.
  2. WP 02A large deliverable must be decomposed to align with sprint cadence and one accounting period. Which boundary choice is most appropriate?

    Debrief answer to open the notes

    1. ACorrect: sizing work packages to one sprint or one reporting period makes them estimable and measurable at the cadence the project reports on.
    2. BDecomposing as far as possible creates overhead and blurs the WBS with the activity list.
    3. COne large package is too big to estimate, track, or measure within a sprint or reporting period.
    4. DContract milestones can be too coarse to align with sprint cadence and accounting periods.
  3. WP 03A regulated subcomponent requires objective acceptance testing. Which minimal WBS dictionary entries best support audit and formal acceptance?

    Debrief answer to open the notes

    1. ACorrect: acceptance criteria, a responsible party, test references, and assumptions are what an auditor needs to trace formal acceptance.
    2. BA high-level description without criteria gives nothing objective to accept against.
    3. CAn owner and a start date do not support testing or acceptance.
    4. DBudget codes and skill levels support cost and staffing, not formal acceptance.
  4. WP 04For repeatable, novel, and regulated deliverables, which decomposition approach is best?

    Debrief answer to open the notes

    1. ACorrect: decomposition depth should follow risk and complexity, with repeatable work kept lighter and novel or regulated work broken down further.
    2. BPerson-level tasks are schedule detail, not WBS decomposition.
    3. CA flat list loses the deliverable hierarchy the WBS exists to provide.
    4. DRegulated items especially need the WBS dictionary to document acceptance.
  5. WP 05You are managing an IT infrastructure deployment project. One of the deliverables is the server configuration for the new data center, and it is ready for review. Where should the completion criteria for this configuration be documented?

    Debrief answer to open the notes

    1. ARequirements documentation states what is needed but is not where each deliverable's completion criteria are recorded.
    2. BCorrect: the WBS dictionary records each element's details, including acceptance criteria that define when it is complete.
    3. CThe schedule holds dates and sequence, not completion criteria.
    4. DThe charter authorizes the project at a high level and does not define deliverable-level criteria.
  6. WP 06On a two-year network upgrade, the first year's sites are fully surveyed, but the second year's sites will be chosen only after the first-year traffic results are in. The sponsor asks for the whole WBS to be broken down to work packages now, so that every site can be estimated. What should the project manager do?

    Debrief answer to open the notes

    1. AWork packages built on invented sites give estimates nobody can trust and guarantee rework; decomposing what is not yet known is false precision.
    2. BThe 100% rule requires the WBS to hold all of the project's work, including the part not yet defined in detail.
    3. CCorrect: this is rolling wave planning. Near-term work is decomposed to work packages, and later work stays as planning packages until it can be.
    4. DHolding back known detail for year one delays estimates and control accounts for work that could be planned today.
  7. WP 07A contract requires a mandated deliverable decomposition. How should the project manager integrate it into the WBS while preserving the 100% rule?

    Debrief answer to open the notes

    1. ADecomposing only to the contract's level may leave work packages too coarse for internal control.
    2. BCorrect: reorganizing the affected branch keeps all work counted once, and re-approval updates the scope baseline formally.
    3. CA flat list under the project level breaks the hierarchy and risks double-counting.
    4. DIgnoring a contractual requirement creates compliance problems and disputes.
  8. WP 08A project manager is identifying all the work packages needed to complete project deliverables. Which project management tool is being used?

    Debrief answer to open the notes

    1. AA Gantt chart displays scheduled activities over time but does not identify the work packages.
    2. BA network diagram shows dependencies between activities, not the decomposition of deliverables.
    3. CA resource breakdown structure organizes resources by category, not the work to be done.
    4. DCorrect: the WBS decomposes deliverables into work packages, so identifying all of them is building the WBS.
  9. WP 09During resource planning for a hospital wing fit-out, the project manager wants one chart that rolls up every crane, electrician crew and pallet of drywall into labor, equipment and material branches, so that resource estimates can be checked branch by branch. Which structure fits this need?

    Debrief answer to open the notes

    1. AAn OBS arranges the performing organization's departments and units and shows which of them own which work packages.
    2. BCorrect: an RBS rolls the project's resources up into branches such as labor, equipment and materials, which is what the estimate check needs.
    3. CA WBS decomposes the project's deliverables and work, not the resources needed to do it.
    4. DA risk breakdown structure groups sources of risk; it shares the RBS abbreviation but is a different tool.

Open a row to answer. Keys: 1–4 or A–D answer, N opens the next row.