HKSM

A top-down technique that uses results from similar past work to estimate cost, duration, or resources for current work. It is fast and low cost but less accurate than parametric or bottom-up methods and relies on expert judgment and comparability.

Definition

See the definition above.

Key Points

• Top-down estimates based on data from similar past projects or components.
• Fast and inexpensive; useful early when limited information is available.
• Lower accuracy than parametric or bottom-up; present as a range with confidence.
• Relies on expert judgment and quality of historical records.
• Adjust for differences in scope, size, complexity, location, technology, and team capability.
• Works for high-level cost, duration, or resource forecasts at project, phase, or feature level.

When to Use

• During initiation or early planning when detailed scope is not yet defined.
• When time or budget for estimating is limited and a quick forecast is needed.
• For feasibility studies, business cases, and Rough Order of Magnitude estimates.
• When comparable internal projects or trusted industry benchmarks exist.
• To cross-check other estimating methods as a sanity check.

How to Estimate

• Identify one or more past projects or components that are truly comparable.
• Validate similarity in scope, complexity, constraints, technology, team skills, and context.
• Normalize historical data for scale, productivity, location, inflation, and timing differences.
• Apply adjustment factors (e.g., +/− percentage) to derive the new cost, duration, or resource estimate.
• Express results as a range with a confidence level and document the basis of estimate.
• Review with subject matter experts, capture assumptions, and update reserves as needed.

Inputs Needed

• High-level scope, objectives, and key constraints.
• Historical data from similar projects (costs, durations, resource usage, productivity).
• Expert judgment from experienced team members or SMEs.
• Organizational process assets such as estimating databases and lessons learned.
• Market rates, inflation indices, and location factors.
• High-level WBS, milestone list, or roadmap.

Outputs Produced

• High-level cost, duration, or resource estimate (single-point or range).
• Confidence level and stated accuracy range with documented assumptions.
• Basis of estimate describing sources, analogs, and adjustment factors.
• Recommended contingency or management reserve at a high level.
• Updates to the assumptions log and risk register.
• Inputs for budget, schedule, and resource plans.

Assumptions

• The selected analog projects are sufficiently similar to the current work.
• Historical data is accurate, complete, and recent enough to be relevant.
• Team capability and productivity are comparable or can be reasonably adjusted for.
• External factors (market rates, regulations, environment) are stable or adjustments are applied.
• No significant unknowns will fundamentally change scope or approach.

Example

A past project delivered a similar product in 10 months at a cost of 800,000. The new effort appears about 15% more complex and current market rates are roughly 5% higher. Adjusting the analog: duration ≈ 10 × 1.15 = 11.5 months; cost ≈ 800,000 × 1.05 × 1.15 ≈ 966,000. Present the estimate as a range, for example 0.8–1.2 million and 10–13 months, with a stated confidence level and documented assumptions and factors.

Pitfalls

• Using non-comparable projects or ignoring key context differences.
• Anchoring on a single analog without cross-checking multiple sources.
• Failing to adjust for scale, complexity, productivity, or inflation.
• Reporting a single precise number without range, confidence, or assumptions.
• Relying on outdated or incomplete historical data.
• Not validating the estimate with experts or actual performance data later.

PMP Example Question

A sponsor asks for a quick, high-level cost forecast during initiation. Detailed requirements are not yet available, but the organization has records from several similar past projects. What should the project manager do?

1. Perform detailed bottom-up estimating after decomposing the work.
2. Use analogous estimating with expert judgment and document assumptions.
3. Apply three-point estimating to each activity in the WBS.
4. Wait until planning is complete and then run a full parametric model.

Correct Answer: B — Use analogous estimating with expert judgment and document assumptions.

Explanation: Analogous estimating provides a quick top-down estimate early in the project using historical data. It suits situations with limited detail, while bottom-up, activity-level, or parametric methods require more information.