Basis of Estimates

The compiled backup that explains how project estimates were developed, including the assumptions and constraints considered, the methods and level of detail used, the estimate ranges, and the expected confidence or accuracy.

Key Points

  • Documents how estimates were derived, including data sources and techniques.
  • Lists key assumptions and constraints that influence the numbers.
  • States the level of detail and estimating approach (e.g., bottom-up, parametric, three-point).
  • Defines estimate ranges and the confidence or accuracy level communicated to stakeholders.

Example

On a building project, the project manager prepares a basis of estimates file that notes: steel prices assumed stable within +/-10% for six months; site access restricted to weekends (constraint); bottom-up estimates for structural work using vendor quotes; three-point estimates for landscaping; an accuracy of -5% to +15% with 70% confidence; and all source data and calculation steps.

PMP Example Question

Which document captures the assumptions, constraints, methods, ranges, and confidence levels used to create the project's estimates?

  1. Basis of Estimates
  2. Cost Baseline
  3. Risk Register
  4. WBS Dictionary

Correct Answer: A — Basis of Estimates

Explanation: The basis of estimates is the supporting documentation that explains how estimates were developed, including assumptions, constraints, methods, ranges, and confidence levels.

Project Management with AI: From Initiation to Closing

Build a practical project management process from initiation to closing with our Project Management: From Initiation to Closing with AI course. Learn how to move from informal project coordination to a structured, repeatable approach using PMBOK-aligned workflows, real examples, and professional templates.

This hands-on course follows a complete project lifecycle. You will learn how to write a project charter, define scope, build a work breakdown structure, develop a schedule, estimate costs, manage risks, engage stakeholders, execute the work, monitor performance, and close the project properly.

You will also learn how to use AI tools to accelerate project management work. The course includes reusable prompts, downloadable templates, assignments, and worked examples that show how project documents connect from one stage to the next.

The course is designed for professionals, team leads, coordinators, analysts, and new project managers who need practical skills they can apply at work. Enroll now and build the confidence to manage projects with structure, clarity, and control.

Explore the Course


Advance your Lean Six Sigma expertise!

HK School of Management helps you take Lean Six Sigma to the next level without the overwhelm. Master advanced statistical tools, Excel-based analysis, and real-world improvement techniques to solve complex problems with confidence. Practical skills, tools, and guidance you can apply right away. Covered by Udemy's 30-day refund policy.

Learn More