Key Takeaways

  • Cost estimating techniques include analogous (least accurate), parametric (uses statistical relationships), bottom-up (most accurate), and three-point (PERT) estimating
  • The cost baseline is the approved time-phased budget used to measure and monitor cost performance, excluding management reserves
  • Contingency reserves address identified risks (known unknowns) and are part of the cost baseline, while management reserves address unidentified risks (unknown unknowns)
  • Estimate accuracy improves through project phases: ROM (-25% to +75%), Budget (-10% to +25%), and Definitive (-5% to +10%)
  • Earned Value Management (EVM) uses Cost Performance Index (CPI = EV/AC) and Schedule Performance Index (SPI = EV/PV) to measure project performance
Last updated: January 2026

Planning & Managing Budget

Cost management ensures the project is completed within the approved budget. It involves estimating costs, determining the budget, and controlling expenditures throughout the project.

Cost Management Processes

ProcessPurposeKey Output
Plan Cost ManagementEstablish policies and procedures for cost managementCost Management Plan
Estimate CostsApproximate monetary resources neededCost Estimates
Determine BudgetAggregate estimates to establish cost baselineCost Baseline
Control CostsMonitor status and manage cost changesWork Performance Information

Cost Estimating Techniques

Comparison of Techniques

TechniqueAccuracyTime/CostBest Used When
Analogous-25% to +75%LowestEarly phases, limited information
Parametric-10% to +25%ModerateHistorical data available
Bottom-Up-5% to +10%HighestDetailed WBS available
Three-PointVariesModerateUncertainty exists

Analogous Estimating (Top-Down)

Uses costs from previous similar projects as the basis for estimates:

Example: "The last website project cost $50,000, so this similar one should cost about $50,000."

AdvantageDisadvantage
Quick and inexpensiveLess accurate
Useful with limited informationDepends on similarity
Good for high-level budgetingMay not account for differences

Parametric Estimating

Uses statistical relationships between historical data and other variables:

Example: Cost per line of code x estimated lines of code

Cost ParameterUnit RateQuantityEstimate
Software coding$50/line10,000 lines$500,000
Testing$20/test case500 cases$10,000
Documentation$100/page200 pages$20,000
Total$530,000

Bottom-Up Estimating

Estimates individual work packages and aggregates them:

Project Total: $530,000
├── Phase 1: $80,000
│   ├── WP 1.1: $30,000
│   └── WP 1.2: $50,000
├── Phase 2: $250,000
│   ├── WP 2.1: $100,000
│   ├── WP 2.2: $100,000
│   └── WP 2.3: $50,000
└── Phase 3: $200,000
    ├── WP 3.1: $150,000
    └── WP 3.2: $50,000
  • Most accurate estimating technique
  • Most time-consuming and expensive
  • Requires detailed WBS

Three-Point Estimating

Uses optimistic, most likely, and pessimistic estimates:

Beta/PERT Formula: E = (O + 4M + P) / 6

Triangular Formula: E = (O + M + P) / 3

Example:

  • Optimistic: $80,000
  • Most Likely: $100,000
  • Pessimistic: $150,000

PERT Estimate = ($80,000 + 4($100,000) + $150,000) / 6 = $103,333


Estimate Accuracy Levels

LevelAccuracy RangeProject PhasePurpose
Rough Order of Magnitude (ROM)-25% to +75%InitiationFeasibility, go/no-go decisions
Budget Estimate-10% to +25%PlanningBudget authorization
Definitive Estimate-5% to +10%Detailed PlanningBaseline, contracts

Progressive Elaboration of Estimates

Estimates become more accurate as the project progresses:

  1. Initiation: ROM estimate based on analogous data
  2. Early Planning: Budget estimate using parametric methods
  3. Detailed Planning: Definitive estimate using bottom-up approach

Cost Baseline Development

The Cost Baseline is the approved, time-phased budget used to measure and monitor project cost performance.

From Estimates to Baseline

ComponentDescriptionIncluded in Baseline?
Activity Cost EstimatesCost of individual activitiesYes
Contingency ReservesFor identified risks (known unknowns)Yes
Cost BaselineTime-phased spending planYes
Management ReservesFor unidentified risks (unknown unknowns)No
Project BudgetCost Baseline + Management ReservesTotal funding

Visual Representation

                   Project Budget
                        ↓
    ┌─────────────────────────────────────┐
    │      Management Reserves            │ ← Unknown unknowns
    ├─────────────────────────────────────┤
    │      Cost Baseline                  │ ← Performance baseline
    │  ┌─────────────────────────────┐    │
    │  │   Contingency Reserves      │    │ ← Known unknowns
    │  ├─────────────────────────────┤    │
    │  │   Activity Cost Estimates   │    │ ← Work package costs
    │  └─────────────────────────────┘    │
    └─────────────────────────────────────┘

Contingency and Management Reserves

Contingency Reserves

  • Address identified risks (known unknowns)
  • Part of the cost baseline
  • PM has authority to use
  • Calculated through risk analysis

Management Reserves

  • Address unidentified risks (unknown unknowns)
  • NOT part of the cost baseline
  • Requires sponsor approval to use
  • Typically a percentage of project budget

Reserve Calculation Example

ComponentAmountCalculation
Base Estimate$400,000Sum of activity estimates
Contingency Reserve$40,00010% for identified risks
Cost Baseline$440,000Base + Contingency
Management Reserve$44,00010% of baseline
Project Budget$484,000Baseline + Management Reserve

Funding Requirements

The funding limit reconciliation ensures that expenditures are reconciled with funding limits:

Funding Patterns

PatternDescriptionExample
Front-loadedMore funding earlyCapital purchases upfront
Back-loadedMore funding laterLabor-intensive completion
LinearEven spending over timeSteady-state operations
S-CurveGradual start, peak, gradual endTypical project pattern

Cash Flow Planning

  • Identify when funds are needed
  • Align with organizational funding cycles
  • Account for payment terms with vendors
  • Consider revenue timing if applicable

Earned Value Management (EVM) Basics

Earned Value Management integrates scope, schedule, and cost to assess project performance.

Key EVM Metrics

MetricFormulaMeaning
Planned Value (PV)Budgeted cost of work scheduledWhat should have been done
Earned Value (EV)Budgeted cost of work performedWhat has been accomplished
Actual Cost (AC)Actual cost of work performedWhat was actually spent

Performance Indices

IndexFormulaInterpretation
Cost Performance Index (CPI)EV / AC> 1.0 = Under budget, < 1.0 = Over budget
Schedule Performance Index (SPI)EV / PV> 1.0 = Ahead of schedule, < 1.0 = Behind schedule

Variance Analysis

VarianceFormulaInterpretation
Cost Variance (CV)EV - ACPositive = Under budget
Schedule Variance (SV)EV - PVPositive = Ahead of schedule

Example

MetricValue
PV (Planned)$100,000
EV (Earned)$80,000
AC (Actual)$90,000
CPI0.89 (over budget by 11%)
SPI0.80 (behind schedule by 20%)
CV-$10,000 (over budget)
SV-$20,000 (behind schedule)

Key Takeaways

  • Analogous is fastest but least accurate; Bottom-up is most accurate but slowest
  • Parametric uses statistical relationships with historical data
  • Three-point accounts for uncertainty using optimistic, most likely, and pessimistic estimates
  • Contingency reserves are for identified risks and are in the cost baseline
  • Management reserves are for unidentified risks and are NOT in the cost baseline
  • EVM uses PV, EV, and AC to measure cost and schedule performance
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Project Budget Components
Test Your Knowledge

Which cost estimating technique is MOST accurate and uses detailed estimates of individual work packages?

A
B
C
D
Test Your Knowledge

A project has a budget of $500,000 including $50,000 in contingency reserves and $45,000 in management reserves. What is the cost baseline?

A
B
C
D
Test Your Knowledge

A project has PV = $200,000, EV = $180,000, and AC = $210,000. What is the Cost Performance Index (CPI) and what does it indicate?

A
B
C
D