Estimation techniques including analogous, parametric, three-point, and expert judgment methods. Provides effort, cost, duration, and complexity estimates for projects, features, and tasks.
Apply estimation techniques (analogous, parametric, three-point, expert judgment) to forecast project effort, cost, and duration. Use when planning projects or features requiring systematic estimates with ranges and confidence levels.
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Systematically estimate effort, cost, duration, and complexity using proven estimation techniques. Supports analogous, parametric, three-point (PERT), and expert judgment methods for projects, features, and tasks.
Estimation is the process of forecasting the resources, time, and cost required to complete work. Good estimation balances:
| Concept | Definition | Use |
|---|---|---|
| Estimate | Best guess given current knowledge | Planning, forecasting |
| Commitment | Promise to deliver by date/cost | Contracts, deadlines |
| Target | Desired outcome to aim for | Goals, objectives |
Key principle: Estimates are ranges with uncertainty, not single-point guarantees.
Estimate based on similar past work:
| Step | Action |
|---|---|
| 1 | Identify similar completed project/feature |
| 2 | Retrieve actual effort/cost/duration |
| 3 | Adjust for differences (complexity, team, technology) |
| 4 | Apply adjustment factor |
Formula:
New Estimate = Historical Actual × Adjustment Factor
Example:
Similar project took 200 hours
New project is ~20% more complex
Estimate = 200 × 1.20 = 240 hours
When to Use: Early phases, limited detail, experienced teams with historical data
Accuracy: +/- 25-50% (improves with good historical data)
Estimate using statistical relationships:
| Element | Description |
|---|---|
| Unit of Work | Measurable element (screen, API, table) |
| Productivity Rate | Effort per unit from historical data |
| Quantity | Number of units to produce |
Formula:
Estimate = Quantity × Productivity Rate
Example:
10 API endpoints × 16 hours/endpoint = 160 hours
Common Productivity Metrics:
| Work Type | Metric | Typical Range |
|---|---|---|
| UI screens | Hours/screen | 8-40 hours |
| API endpoints | Hours/endpoint | 4-24 hours |
| Database tables | Hours/table | 4-16 hours |
| Test cases | Hours/test | 0.5-4 hours |
| Documentation pages | Hours/page | 2-8 hours |
When to Use: Repeatable work, good historical data, similar technology
Accuracy: +/- 15-25% (with calibrated rates)
Estimate using optimistic, most likely, and pessimistic values:
| Value | Symbol | Definition |
|---|---|---|
| Optimistic | O | Best case, everything goes right |
| Most Likely | M | Most probable outcome |
| Pessimistic | P | Worst case, problems occur |
PERT Formula (Weighted Average):
Expected = (O + 4M + P) / 6
Standard Deviation = (P - O) / 6
Example:
O = 5 days, M = 8 days, P = 17 days
Expected = (5 + 4×8 + 17) / 6 = 9 days
Std Dev = (17 - 5) / 6 = 2 days
Confidence Intervals:
| Confidence | Calculation | Example (E=9, SD=2) |
|---|---|---|
| 68% | E ± 1 SD | 7-11 days |
| 95% | E ± 2 SD | 5-13 days |
| 99.7% | E ± 3 SD | 3-15 days |
When to Use: Uncertain work, new technology, need to communicate risk
Accuracy: Provides explicit uncertainty range
Estimate using collective expert knowledge:
Wideband Delphi Process:
| Round | Activity |
|---|---|
| 1 | Experts estimate independently |
| 2 | Collect and share anonymous estimates |
| 3 | Discuss high/low outliers, share rationale |
| 4 | Re-estimate independently |
| 5 | Repeat until convergence (or average) |
Planning Poker (Agile):
| Step | Action |
|---|---|
| 1 | Present item to estimate |
| 2 | Discuss briefly (2-5 minutes) |
| 3 | Each team member selects card privately |
| 4 | Reveal simultaneously |
| 5 | Discuss outliers |
| 6 | Re-vote until consensus |
Common Scales:
| Scale Type | Values |
|---|---|
| Fibonacci | 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 |
| Modified Fibonacci | 0, 0.5, 1, 2, 3, 5, 8, 13, 20, 40, 100 |
| T-shirt | XS, S, M, L, XL, XXL |
| Powers of 2 | 1, 2, 4, 8, 16, 32, 64 |
When to Use: Complex work, multiple perspectives needed, team alignment
Estimate based on functional size (for larger systems):
| Component | Description | Weight Range |
|---|---|---|
| External Inputs | Data entering system | 3-6 |
| External Outputs | Data leaving system | 4-7 |
| External Inquiries | Read-only queries | 3-6 |
| Internal Files | Logical data stores | 7-15 |
| External Interfaces | Shared data | 5-10 |
Process:
When to Use: Large projects, formal contracts, industry benchmarking
Relative complexity/effort measure:
| Points | Relative Size | Example |
|---|---|---|
| 1 | Trivial | Fix typo, config change |
| 2 | Simple | Simple bug fix, minor feature |
| 3 | Moderate | Standard feature, moderate complexity |
| 5 | Complex | Multi-component feature |
| 8 | Very complex | Integration work, significant unknowns |
| 13 | Epic-sized | Consider breaking down |
| 21+ | Too large | Must decompose |
Baseline: Pick a well-understood story as reference (e.g., "this is a 3")
Velocity: Story points completed per iteration (used for forecasting)
Quick relative sizing for roadmap planning:
| Size | Effort Range | Duration Range |
|---|---|---|
| XS | 1-4 hours | < 1 day |
| S | 0.5-2 days | 1-2 days |
| M | 2-5 days | 3-5 days |
| L | 1-2 weeks | 1-2 weeks |
| XL | 2-4 weeks | 2-4 weeks |
| XXL | 1-3 months | Too big, decompose |
## Estimation Request
**Item:** [What's being estimated]
**Requester:** [Who needs the estimate]
**Purpose:** [Planning/budgeting/commitment]
**Deadline:** [When estimate is needed]
**Precision:** [ROM/Budget/Definitive]
### Scope Definition
- **In Scope:** [What's included]
- **Out of Scope:** [What's excluded]
- **Assumptions:** [Key assumptions]
- **Constraints:** [Known constraints]
| Situation | Recommended Technique |
|---|---|
| Early project phase | Analogous + T-shirt sizing |
| Detailed requirements | Parametric + Three-point |
| Agile backlog | Story points + Planning poker |
| New technology/domain | Expert judgment + Three-point |
| Contract/budget | Function points + Parametric |
Break down into estimable units (half-day to 2-week chunks)
Use selected technique(s) from above
## Contingency Calculation
| Risk Level | Contingency | When to Use |
|------------|-------------|-------------|
| Low | 10-15% | Well-understood, experienced team |
| Medium | 20-30% | Some unknowns, new team members |
| High | 40-50% | Significant unknowns, new technology |
| Very High | 75-100% | Research, innovation, first-of-kind |
## Estimate Summary
**Effort:** 160-200 hours (confidence: 80%)
**Duration:** 4-5 weeks (with 2 developers)
**Cost:** $24,000-$30,000
**Key Risks:**
- API integration complexity unknown
- Dependency on third-party availability
## Estimation Assumptions
1. Requirements are stable and complete
2. Team has 80% availability (20% overhead)
3. No major technology changes
4. Dependencies delivered on time
5. [Additional assumptions...]
**If assumptions change, estimate should be revisited.**
## Estimation Summary
**Item:** [Feature/Project name]
**Date:** [ISO date]
**Estimator:** estimation-analyst
**Technique:** [Technique used]
### Estimate
| Dimension | Low | Expected | High | Confidence |
|-----------|-----|----------|------|------------|
| Effort | 120h | 160h | 220h | 80% |
| Duration | 4w | 5w | 7w | 80% |
| Cost | $18K | $24K | $33K | 80% |
### Basis of Estimate
- **Historical Reference:** [Similar past work]
- **Productivity Rate:** [If parametric]
- **Expert Input:** [Who contributed]
### Assumptions
1. [Assumption 1]
2. [Assumption 2]
### Risks Affecting Estimate
| Risk | Impact on Estimate |
|------|-------------------|
| [Risk 1] | +20% if occurs |
| [Risk 2] | +15% if occurs |
### Recommendations
1. [Next steps for refining estimate]
2. [When to re-estimate]
estimation:
version: "1.0"
date: "2025-01-15"
item: "User Dashboard Feature"
estimator: "estimation-analyst"
technique: "three_point"
scope:
description: "Interactive user dashboard with analytics"
in_scope:
- "Dashboard UI components"
- "Data visualization"
- "User preferences"
out_of_scope:
- "Backend analytics engine"
- "Real-time updates"
assumptions:
- "API endpoints available"
- "Design mockups complete"
estimates:
effort:
optimistic: 120
most_likely: 160
pessimistic: 240
expected: 166
unit: "hours"
std_deviation: 20
duration:
optimistic: 3
most_likely: 4
pessimistic: 6
expected: 4.2
unit: "weeks"
cost:
expected: 24000
range_low: 18000
range_high: 36000
currency: "USD"
confidence: 0.80
contingency: 0.20
breakdown:
- component: "UI Components"
effort: 60
technique: "parametric"
rate: "15h/component"
quantity: 4
- component: "Data Integration"
effort: 40
technique: "analogous"
reference: "PROJ-123"
- component: "Testing"
effort: 40
technique: "percentage"
percentage: 0.25
risks:
- risk: "API complexity higher than expected"
probability: 0.3
impact_hours: 30
- risk: "Design changes during development"
probability: 0.2
impact_hours: 20
historical_comparison:
similar_item: "Admin Dashboard"
actual_effort: 180
adjustment_factor: 0.9
## Effort Breakdown
| Component | Technique | Estimate | Contingency | Total |
|-----------|-----------|----------|-------------|-------|
| UI Components | Parametric | 60h | 12h | 72h |
| Data Integration | Analogous | 40h | 10h | 50h |
| Testing | % of Dev | 40h | 8h | 48h |
| Documentation | Parametric | 16h | 4h | 20h |
| **Subtotal** | | **156h** | **34h** | **190h** |
| Management Overhead | 10% | | | 19h |
| **Total** | | | | **209h** |
Estimate accuracy improves as project progresses:
| Phase | Accuracy Range |
|---|---|
| Initial concept | 0.25x - 4x |
| Approved project | 0.5x - 2x |
| Requirements complete | 0.67x - 1.5x |
| Detailed design | 0.8x - 1.25x |
| Code complete | 0.9x - 1.1x |
Implication: Early estimates need wider ranges; refine as knowledge grows.
| Level | Accuracy | When Used |
|---|---|---|
| ROM (Rough Order of Magnitude) | -25% to +75% | Initial budgeting |
| Budget | -10% to +25% | Project approval |
| Definitive | -5% to +10% | Execution baseline |
| Pitfall | Prevention |
|---|---|
| Single-point estimates | Always provide ranges |
| Optimism bias | Use historical data, add contingency |
| Anchoring | Estimate before seeing others' estimates |
| Planning fallacy | Include realistic overhead and risks |
| Scope creep | Document assumptions, re-estimate on changes |
| Precision theater | Match precision to actual knowledge |
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