WBS

What is WBS?

WBS (Work Breakdown Structure) is a hierarchical decomposition of an entire project into smaller and smaller elements — from the project goal (level 0) through major phases or deliverables (level 1), sub-projects (level 2), down to individual work packages (level 3 and beyond) that are sufficiently small for a realistic estimate of time and cost.

The key rule of WBS is the “100% rule” — the sum of the scope of all packages at any level must exactly correspond to the scope of the parent package, with no gaps or overlaps. WBS is most commonly seen in larger construction and IT projects — in public procurement it is often a mandatory appendix to a tender.

Example WBS for an ERP implementation:

• 1.0 Analysis
  • 1.1 Department workshops
  • 1.2 Functional requirements document
• 2.0 Configuration
  • 2.1 Accounting
  • 2.2 Warehouse
• 3.0 Data migration
• 4.0 Testing and training

When it is used

WBS is the starting point of every serious project — from it a Gantt chart, budget, and responsibility matrix (RACI) can be built. Without WBS a project typically loses control of scope (scope creep).

See the Planning module, the Quotes module, and the construction industry page.

Related terms

• Gantt — the time plan built over the WBS. See /en/glossary/gantt.
• Kanban — operational management of tasks defined in the WBS. See /en/glossary/kanban.
• S&OP — the planning cycle that uses WBS for each project. See /en/glossary/s-and-op.

In Modulario

The Planning module in Modulario supports multi-level WBS hierarchies directly — each package has its owner, estimated time, assigned resources, and costs that aggregate up to the Quote.

Modulario allows WBS to be exported to Excel or PDF for public tender appendices, imported from MS Project, and synchronised with the Quote — a change to a cost estimate in the project budget is immediately reflected in the final price for the client.

Properly sized WBS packages follow the 8/80 rule — a package must take at least 8 hours of work and no more than 80 hours. Smaller packages are operationally unmanageable; larger ones do not provide sufficient visibility.