What Is a Resource Breakdown Structure?

A Resource Breakdown Structure (RBS) is a hierarchical representation of resources organized by category and type. In PMBOK 8, the RBS is a tool used in the Project Resource Management performance domain to provide a structured view of all resources — human, material, equipment, and financial — grouped logically for planning, tracking, and reporting. Like a WBS decomposes scope, the RBS decomposes resource consumption, enabling cost tracking by resource category and supporting resource optimization analysis. The RBS is particularly useful for identifying resource pools, spotting over-reliance on specific resource types, and aligning resource planning with organizational capacity management.

What's Inside This Resource Breakdown Structure Example

This Resource Breakdown Structure example covers Project Phoenix — MCG's $72,250 website launch, March 17 to June 13, 2025. The spreadsheet presents a three-level RBS:

• Level 1: Project Phoenix Resources (total)
• Level 2: Human Resources, Equipment & Software, Materials, External/Vendor
• Level 3 — Human Resources: Project Management (Alex Morgan), UX Design, Development, Content, Quality Assurance, Data Migration
• Level 3 — Equipment & Software: Development Workstations, Staging Server, QA Devices, Software Licenses (CMS, PM Tool, Design Software, Testing Tools)
• Level 3 — External/Vendor: BrightFrame (design vendor), Hosting Provider, Plugin Vendors

The RBS is accompanied by a cost allocation tab showing actual spend by Level 2 and Level 3 category: Human Resources ($48,200 / 73%), External/Vendor ($20,900 / 31%), Equipment & Software ($3,150 / 5%). These percentages are benchmarked against industry norms for web projects of similar scope.

How Alex Morgan Used This Resource Breakdown Structure

Alex Morgan built the RBS during planning as a companion to the WBS. While the WBS answered "what work will be done," the RBS answered "what resources will perform it." The two structures were cross-referenced in the Resource Requirements spreadsheet, ensuring every work package had a resource category assigned before cost estimating began.

The RBS proved most valuable for two analysis purposes:

• Vendor dependency analysis: The External/Vendor category at Level 2 aggregated all BrightFrame and hosting costs into a single view. When CR-001 (blog module) was evaluated, Alex used the RBS to quickly assess whether the new work required additional vendor engagement or could be handled internally. The answer was internal (Lead Developer), which informed the cost estimate for CR-001.
• Resource optimization: The RBS showed that 73% of project cost was human labor — typical for professional services. The breakdown by specialty (Development 32% of total, UX 14%, Content 10%) gave Riley Park a clear picture of where MCG's investment was going: primarily into technical delivery, which aligned with the project's strategic goal of launching a technically superior website.

Download and Customize

This Resource Breakdown Structure example is available as a free download. Use it as a reference to build your own RBS, or start with the blank template and customize it for your project's resource categories.

• Download the Resource Breakdown Structure Template — PMBOK 8 (blank, ready to use)
• Read the article: Resource Breakdown Structure in PMBOK 8 — Guide and Best Practices

Resource Breakdown Structure Example: Key Takeaways

The Resource Breakdown Structure is the financial lens on a project. Project Phoenix's RBS revealed that 73% of cost was human labor — which meant the primary cost risk was labor estimate accuracy, not vendor pricing or equipment costs. Knowing this, Alex invested the most estimating rigor in the labor estimates and built the contingency reserve primarily to cover labor overruns (like the content migration underestimate). The RBS made that risk concentration visible in a way that a flat cost spreadsheet would not. Build an RBS early; it will tell you where your project's financial risk lives before a single line of work begins.

Want to go deeper? The PMBOK Guide 8th Edition is the definitive reference for modern project management. Get your copy and use it alongside these examples to build a solid, practical understanding of every performance domain.