---
ref_id: PR11
ref_type: Process
ref_name: "Estimate Activity Durations"
version: "1.0.0"
status: Active
pmbok8_source: "PMBOK8 Guide §2.3.2.2"
companion_ref_shortcode: PG-APG-5.9
related_skills:
  - SKL-03-06
related_artifacts:
  - A15
file_path: "reference/processes/PR11-estimate-activity-durations.md"
---
# PR11 — Estimate Activity Durations

## Classification
- **Performance Domain:** Schedule
- **Process Group:** Planning
- **PMBOK 8 Reference:** Section 2.3.2.2 (Develop Schedule — Step 3)
- **Process Groups Practice Guide Reference:** Section 5.9

---

## Purpose
Estimate Activity Durations is the process of estimating the number of work periods needed to complete individual activities with estimated resources. The key benefit is that it provides the amount of time each activity will take to complete.

---

## Inputs
- Project management plan (schedule management plan, scope baseline)
- Project documents: activity attributes, activity list, assumption log, lessons learned register, milestone list, project team assignments, resource breakdown structure, resource calendars, resource requirements, risk register
- Enterprise environmental factors
- Organizational process assets

---

## Tools & Techniques
- Expert judgment
- Analogous estimating
- Parametric estimating
- Three-point estimating (PERT)
- Bottom-up estimating
- Data analysis (alternatives analysis, reserve analysis)
- Decision making (voting)
- Meetings

---

## Outputs
- Duration estimates
- Basis of estimates
- Project documents updates (activity attributes, assumption log, lessons learned register)

---

## Key Concepts
- Duration estimates use scope of work, resource types/skill levels, estimated resource quantities, and resource calendars as primary inputs.
- Estimation considers: law of diminishing returns, number of resources, advances in technology, documentation, level of decomposition, and cognitive bias (planning fallacy, Parkinson's Law, Student Syndrome).
- Three-point estimating formula (triangular distribution): **tE = (tO + tM + tP) / 3**
- Duration estimates do not include leads or lags.
- Estimates are progressively elaborated throughout the project.

---

## Adaptive Considerations
- In adaptive approaches, effort/duration is estimated using story points, T-shirt sizing, or planning poker.
- Velocity data from previous iterations informs future duration estimates.

---

## Source Traceability
- PMBOK 8: Section 2.3.2.2 (Steps for Developing the Schedule — Step 3)
- Process Groups Practice Guide: Section 5.9

---

## Cross-References

| Related Item | Type | Relationship |
|---|---|---|
| A15 | Artifact | Primary artifact produced or updated by this process |
| SKL-03-06 | Skill | Skill that executes this process |

## Practitioner Notes

Practitioners executing this process should seek answers to the following questions:
1. Are estimates based on validated activity attributes and a current resource calendar?
2. Have analogous, parametric, and three-point methods been considered and documented?
3. Are cognitive biases (Parkinson's Law, Student Syndrome, planning fallacy) explicitly mitigated?
4. Is the basis of estimates documented for future audit and replanning?
5. Have adaptive velocity or story-point data been incorporated where applicable?

## Change Log

| Version | Date | Description | Author |
|---|---|---|---|
| 1.0.1 | 2026-06-03 | Added Cross-References, Practitioner Notes, and Change Log sections (F-12 Batch 4) | PMO Director |
