Define the Estimate's Purpose
Establish why the cost estimate is needed and how it will be used. This foundational step determines the estimate's scope, level of detail, and the decision it will support — whether for budgeting, milestone review, contract negotiation, or source selection. A clearly defined purpose ensures every subsequent step aligns with the decision-maker's needs.
Develop the Estimating Plan
Create a comprehensive plan that outlines the approach, schedule, and resources needed to complete the cost estimate. The estimating plan serves as the project management roadmap for the estimating effort itself, ensuring adequate time, expertise, and data sources are identified before work begins.
Define Program Characteristics
Document the technical and programmatic characteristics that drive cost. This step translates system requirements, performance parameters, and technical specifications into cost-relevant attributes. Understanding what the program will do and how it will be built is essential for selecting appropriate cost estimating relationships.
Determine the Estimating Structure (WBS)
Establish the Work Breakdown Structure (WBS) that will serve as the framework for organizing and presenting the estimate. The WBS provides a hierarchical decomposition of the total program into manageable, estimable elements. A well-constructed WBS ensures completeness, prevents double-counting, and enables cross-program comparisons.
Identify Ground Rules and Assumptions
Document the ground rules, assumptions, and constraints that define the boundaries and conditions under which the estimate is valid. Ground rules are facts or directives (e.g., base year dollars, inflation rates), while assumptions fill knowledge gaps when facts are unavailable. Clear documentation of both is essential for estimate transparency and credibility.
Obtain Data
Collect, validate, and normalize the data needed to develop the cost estimate. Data is the foundation of any credible estimate — the quality of the estimate can never exceed the quality of the data. This step involves identifying historical cost data, technical data, and programmatic data from multiple sources and assessing their relevance and reliability.
Develop the Point Estimate
Apply the selected estimating methodologies to the collected data to produce a single point estimate for each WBS element. This step involves building cost estimating relationships (CERs), applying learning curves, developing labor-hour estimates, and aggregating bottom-up engineering estimates. The point estimate represents the most likely cost before risk and uncertainty adjustments.
Conduct Sensitivity Analysis
Test how changes in key assumptions and input parameters affect the total cost estimate. Sensitivity analysis identifies which variables have the greatest impact on cost, helping decision-makers understand where estimation uncertainty is concentrated and which assumptions most need validation or risk mitigation.
Conduct Risk and Uncertainty Analysis
Quantify the range of possible costs by modeling the combined effect of uncertainties across all cost elements. Unlike sensitivity analysis (which varies one factor at a time), risk analysis uses Monte Carlo simulation or similar techniques to produce a probability distribution of total program cost, enabling the selection of a confidence level for budgeting.
Document the Estimate
Create comprehensive documentation that allows an independent reviewer to understand, replicate, and evaluate the estimate. Documentation is not an afterthought — it is a GAO best practice that transforms an estimate from a personal opinion into an auditable, defensible analysis. Complete documentation is required for estimates to pass GAO and IG scrutiny.
Present Estimate for Management Approval
Brief the cost estimate to program leadership and stakeholders for review and approval. The presentation should clearly communicate the bottom-line cost, the confidence level, key drivers and risks, and the comparison to independent estimates. This is where the estimating team's credibility is established and where budgetary decisions are informed.
Update the Estimate to Reflect Actual Costs
Continuously update the cost estimate as the program progresses by incorporating actual cost data, schedule changes, and technical refinements. An estimate is a living document that should be refreshed at each major milestone, significant program change, or annually at minimum. Comparing estimates to actuals feeds lessons learned back into future estimating.
About the GAO Cost Estimating Guide
The GAO Cost Estimating and Assessment Guide (GAO-20-195G) establishes best practices for developing and managing cost estimates for federal capital programs. Originally published in 2009 and updated in 2020, the guide defines a 12-step process that produces cost estimates meeting four characteristics: comprehensive, well-documented, accurate, and credible.
For government contractors, understanding this process is essential because agency cost estimates directly influence budget decisions, contract pricing, and program affordability assessments. Contractors who align their own cost proposals with GAO best practices produce more defensible estimates, experience fewer DCAA audit findings, and negotiate more effectively with contracting officers.