5th Edition PMBOK Guide–Chapter 6: Process 6.4 Estimate Activity Resources

1.  Introduction

Once the activities have been identified in process 6.2 Define Activities, it is necessary to find out what resources will be needed to perform them.  That is where this process 6.4 Estimate Activity Resources comes in.

It is not only the amount of resources, but the schedule of when they are available that are both needed to find out how long a particular activity will take.

2.  Inputs, Tools & Techniques, and Outputs

Here is a brief recap from the 5th Edition PMBOK® Guide of the inputs, tools & techniques, and outputs necessary for this process.  A lot of the inputs comes from the process 6.2 Define Activities, but some come from processes from other knowledge area management processes, such as Cost, Procurement, Human Resources, and even Risk Management.

For the tools & techniques, the ubiquitous “Expert Judgment” is used when it comes to estimating resources.  For rough estimates based on previous projects or industry-wide information there are tools, but the most accurate technique is that of Bottom-Up Estimating.  It is the most accurate, but also takes the most amount of time to do.


1. Schedule Management Plan Identifies the level of accuracy and the units of measure for the resources to be used.
2. Activity List Includes all scheduled activities on the project that will need resources.  This is an output of process 6.2 Define Activities
3. Activity Attributes Provides data to be used in estimating the resources required for each activity.  This is an output of process 6.2 Define Activities.
4. Resource Calendars Identifies the working days and shifts when resources are available.  Input from Human Resources and Procurements Management.
5. Risk Register Risk events may impact resource availability.  Input from Risk Management.
6. Activity Cost Estimates Cost of resources may impact resource selection.  Input from Cost Management.
6. EEFs Resource location, availability, skills.
7. OPAs
  • Project files (historical information on previous projects)
  • Policies, procedures and guidelines regarding staffing, equipment and supplies rental
1. Expert Judgment Any person with expertise in resource planning and estimating can help assess resource inputs.
2. Alternative Analysis Many schedule activities have different alternatives methods of accomplishment in terms of resources.
3. Published Estimating Data Unit costs of resources and production rates for an industry may be obtained from professional organizations.
4. Bottom-Up Estimating Aggregates the cost or duration of the project by aggregating the cost or duration of the individual work packages.
5. Project Management Information System (PMIS) Used to help plan, organize, and manage resources.
1. Activity Resource Requirements Identifies the type and quantity of resources needed for each activity in a work package.
2. Resource Breakdown Structure Hierarchical representation of resources by category and type, typical categories being:  labor, material, equipment, supplies.
3. Project Documents Updates
  • Activity list
  • Activity attributes
  • Resource calendars


Once the outputs of the Activity Resource Requirements and Resource Breakdown Structure are complete, these then become inputs in the next process, that of 6.5 Estimate Activity Durations, which is the subject of the next post.

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