Estimate Activity Resources

Estimate Activity Resources

Introduction: Why This Matters

A schedule is only as realistic as the resources behind it. The Estimate Activity Resources process determines the type and quantity of resources needed for each activity, including people, equipment, materials, and facilities. Accurate resource estimates support credible duration estimates, realistic cost models, and an executable schedule.

On the PMP exam, this process is frequently tested through scenarios that check whether you understand the difference between estimating how many resources are required in Planning and acquiring those resources later in Executing. In practice, weak resource estimation leads to overallocated teams, idle equipment, and cascading schedule delays (Project Management Institute, 2021).

Purpose and Objectives

Primary Purpose: Determine the resources and quantities required to perform each activity.

Key Objectives:

• Identify the types of resources required, such as roles, skill sets, equipment models, and material categories.
• Quantify the amounts and levels of resources, such as number of people by role, machine hours, or material volumes.
• Reflect availability constraints using resource calendars and organizational policies.
• Produce a defensible basis of estimates that ties assumptions and methods to the numbers.
• Create the Resource Breakdown Structure and resource requirements that feed duration, cost, and schedule development.

Overview

Estimate Activity Resources converts the activity list and WBS into specific resource types and quantities, producing structured requirements that drive durations, costs, and the schedule.

• Inputs: Resource management plan, scope baseline, activity list and attributes, cost estimates, resource calendars, risk register, enterprise environmental factors, and organizational process assets.
• Tools and Techniques: Expert judgment, bottom up, analogous and parametric estimating, data analysis, project management information systems, and workshops.
• Outputs: Resource requirements, basis of estimates, Resource Breakdown Structure, and project document updates.

Inputs, Tools and Techniques, Outputs (ITTOs)

Inputs

• Resource management plan
• Scope baseline, including WBS and WBS dictionary
• Activity list and activity attributes
• Cost estimates and basis of estimates
• Resource calendars
• Risk register
• Enterprise environmental factors
• Organizational process assets

Tools and Techniques

• Expert judgment from functional managers, SMEs, and vendors.
• Bottom up estimating at the work package or activity level.
• Analogous estimating based on similar past efforts.
• Parametric estimating using productivity rates and unit costs.
• Data analysis, including alternatives analysis and make or buy considerations.
• Project Management Information System for modeling resource needs and availability.
• Meetings and workshops with team leads and suppliers.

Outputs

• Resource requirements by activity and aggregated where needed.
• Basis of estimates documenting methods, assumptions, and ranges.
• Resource Breakdown Structure (RBS) categorized by resource type.
• Project document updates such as activity attributes, risk register, and cost estimates.

Characteristics

• Detail driven: Built at the activity level, then rolled up to control accounts and project view.
• Calendar aware: Uses resource calendars and constraints to keep estimates realistic.
• Technique rich: Combines bottom up, parametric, and analogous approaches for defensible numbers.
• Highly integrative: Directly feeds duration, cost, schedule, and risk analysis.

What You Produce and How You Use It

Resource Requirements

A structured list of the people, equipment, and materials required for each activity, including quantities and timing. Common fields include:

• Activity ID and name.
• Role or skill, equipment model, or material type.
• Quantity or effort required.
• Needed dates or time windows.
• Special constraints or certifications.

Basis of Estimates

The narrative that explains how you arrived at the numbers. It should cite historical data, productivity assumptions, vendor quotes, and risk considerations. This protects credibility when estimates are challenged and supports future change discussions.

Resource Breakdown Structure

A hierarchical chart of resource categories. Example top levels: People, Equipment, Materials, Facilities, Services. The RBS helps stakeholders see where resource demand will concentrate across the project.

Practical Example: Campus Fiber Upgrade

Context: A university is replacing copper cabling with fiber across ten buildings.

Selected activities and estimates:

• Pull fiber trunk lines
  • Resources: 2 fiber technicians, 1 lift, 1 cable puller.
  • Quantity: 2 technicians for 15 days, lift for 120 hours, puller for 120 hours.
  • Basis: Historical productivity of 150 meters per crew per day and 1 lift per crew.
• Terminate and test fiber
  • Resources: 2 fusion splicers, 1 test kit, 2 technicians.
  • Quantity: 2 splicers for 8 days, 2 technicians for 8 days.
  • Basis: Vendor data with 24 terminations per day per splicer and 15 percent contingency.
• Closet build outs
  • Resources: Carpenter crew, racks, cooling units.
  • Quantity: 1 crew for 5 days per building, 10 racks, 10 mini split units.
  • Basis: Facilities standards and past build outs for similar buildings.

Outcome: The team aggregates resource requirements by week, identifies a clash for the single available lift in weeks 3 and 4, and flags the need to resequence activities or rent a second lift. The resource plan then feeds duration refinement, cost updates, and schedule development.

Techniques in Action

Bottom up estimating

Start with each activity’s resource needs, then roll up to control accounts and the project level. This is most accurate when the WBS and activity definitions are clear.

Parametric estimating

Apply known productivity rates. Examples include:

• Twenty story points per developer per sprint.
• Two hours per 100 meters of cable.
• Five inspection minutes per manufactured unit.

Analogous estimating

Use historical ratios from similar projects when detail is limited. Validate with SMEs and adjust for complexity and context.

Alternatives analysis

Compare different mixes of resources. Examples:

• Two senior developers for 5 weeks versus three intermediate developers for 6 weeks.
• Lease versus buy specialized equipment.

Common Pitfalls

Equating effort with duration

• Mistake: Assuming 80 hours of effort equals two calendar weeks.
• Fix: Consider resource availability and parallelization. Duration depends on how many qualified resources can work concurrently.

Ignoring resource calendars

• Mistake: Estimating without accounting for holidays, maintenance windows, or part time staff.
• Fix: Use up to date calendars and confirm with functional managers.

Under specifying skill levels and certifications

• Mistake: “Two engineers” with no indication of skills or licenses.
• Fix: Specify roles, skills, and any required certifications or clearances in the resource requirements.

Single point estimating

• Mistake: One number with no documented range or basis.
• Fix: Use three point or parametric ranges and always capture the basis of estimates.

Optimism bias and learning curve blindness

• Mistake: Assuming immediate full productivity.
• Fix: Include ramp up time and training where appropriate.

Quick Recap Table

Key Takeaways

• Estimate Activity Resources determines the types and quantities of resources per activity and aggregates them appropriately.
• Outputs such as resource requirements, basis of estimates, and the Resource Breakdown Structure directly inform durations, costs, and the schedule.
• Always ground estimates in calendars, productivity rates, and risk responses to avoid optimism bias.
• On the PMP exam, keep clear the separation between estimating resources in Planning and acquiring resources in Executing.

Next Step

With resource quantities defined, the next Planning process is Plan Communications Management, which specifies how information will be created, tailored, and distributed so that stakeholders remain aligned and engaged throughout the project.

Bibliography

Project Management Institute. (2021). A Guide to the Project Management Body of Knowledge (PMBOK® Guide) (7th ed.). Project Management Institute.