project-estimation
Estimate project scope, timeline, and resource requirements using multiple estimation techniques including bottom-up, top-down, and analogous estimation methods for accurate project planning.
Installation
Copy to your project
cp -r skills/project-estimation/ /your-project/.claude/skills/project-estimation/Project Estimation
Overview
Accurate project estimation determines realistic timelines, budgets, and resource allocation. Effective estimation combines historical data, expert judgment, and structured techniques to minimize surprises.
When to Use
- Defining project scope and deliverables
- Creating project budgets and timelines
- Allocating team resources
- Managing stakeholder expectations
- Assessing project feasibility
- Planning for contingencies
- Updating estimates during project execution
Instructions
1. Three-Point Estimation (PERT)
# Three-point estimation technique for uncertainty
class ThreePointEstimation:
@staticmethod
def calculate_pert_estimate(optimistic, most_likely, pessimistic):
"""
PERT formula: (O + 4M + P) / 6
Weighted toward most likely estimate
"""
pert = (optimistic + 4 * most_likely + pessimistic) / 6
return round(pert, 2)
@staticmethod
def calculate_standard_deviation(optimistic, pessimistic):
"""Standard deviation for risk analysis"""
sigma = (pessimistic - optimistic) / 6
return round(sigma, 2)
@staticmethod
def calculate_confidence_interval(pert_estimate, std_dev, confidence=0.95):
"""
Calculate confidence interval for estimate
95% confidence ≈ ±2 sigma
"""
z_score = 1.96 if confidence == 0.95 else 2.576
margin = z_score * std_dev
return {
'estimate': pert_estimate,
'lower_bound': round(pert_estimate - margin, 2),
'upper_bound': round(pert_estimate + margin, 2),
'range': f"{pert_estimate - margin:.1f} - {pert_estimate + margin:.1f}"
}
# Example
optimistic = 10 # best case
most_likely = 20 # expected
pessimistic = 40 # worst case
pert = ThreePointEstimation.calculate_pert_estimate(optimistic, most_likely, pessimistic)
std_dev = ThreePointEstimation.calculate_standard_deviation(optimistic, pessimistic)
confidence = ThreePointEstimation.calculate_confidence_interval(pert, std_dev)
print(f"PERT Estimate: {pert} days")
print(f"Standard Deviation: {std_dev}")
print(f"95% Confidence Range: {confidence['range']}")
2. Bottom-Up Estimation
// Bottom-up estimation from detailed task breakdown
class BottomUpEstimation {
constructor(project) {
this.project = project;
this.tasks = [];
this.workBreakdownStructure = {};
}
createWBS() {
// Work Breakdown Structure example
return {
level1: 'Full Project',
level2: ['Planning', 'Design', 'Development', 'Testing', 'Deployment'],
level3: {
'Development': [
'Backend API',
'Frontend UI',
'Database Schema',
'Integration'
],
'Testing': [
'Unit Testing',
'Integration Testing',
'UAT',
'Performance Testing'
]
}
};
}
estimateTasks(tasks) {
let totalEstimate = 0;
const estimates = [];
for (let task of tasks) {
const taskEstimate = this.estimateSingleTask(task);
estimates.push({
name: task.name,
effort: taskEstimate.effort,
resources: taskEstimate.resources,
risk: taskEstimate.risk,
duration: taskEstimate.duration
});
totalEstimate += taskEstimate.effort;
}
return {
totalEffortHours: totalEstimate,
totalWorkDays: totalEstimate / 8,
taskDetails: estimates,
criticalPath: this.identifyCriticalPath(estimates)
};
}
estimateSingleTask(task) {
// Base effort
let effort = task.complexity * task.scope;
// Adjust for team experience
const experienceFactor = task.teamExperience / 100; // 0.5 to 1.5
effort = effort * experienceFactor;
// Adjust for risk
const riskFactor = 1 + (task.riskLevel * 0.1);
effort = effort * riskFactor;
return {
effort: Math.ceil(effort),
resources: Math.ceil(effort / 8), // days
risk: task.riskLevel,
duration: Math.ceil(effort / (8 * task.teamSize))
};
}
identifyCriticalPath(estimates) {
// Return tasks with longest duration
return estimates
.sort((a, b) => b.duration - a.duration)
.slice(0, 5);
}
}
3. Analogous Estimation
Analogous Estimation Template:
Historical Project Comparison:
Current Project:
Type: E-commerce Payment System
Complexity: High
Scope: Medium
Team Size: 5 developers
Similar Historical Projects:
Project A (2 years ago):
Type: E-commerce Shipping System
Complexity: High
Scope: Medium
Team Size: 5 developers
Actual Duration: 16 weeks
Actual Cost: $180,000
Lessons: Underestimated integration work
Project B (1 year ago):
Type: Payment Gateway Integration
Complexity: High
Scope: Small
Team Size: 3 developers
Actual Duration: 8 weeks
Actual Cost: $95,000
Lessons: Security review added 2 weeks
Adjustments:
- Current project 20% larger than Project B
- Similar complexity and team composition
- Estimated Duration: 10-12 weeks
- Estimated Cost: $120,000-$140,000
Confidence Level: 75% (medium, due to some differences)
4. Resource Estimation
// Resource allocation and estimation
class ResourceEstimation {
calculateResourceNeeds(projectDuration, tasks) {
const resourceMap = {
'Senior Developer': 0,
'Mid-Level Developer': 0,
'Junior Developer': 0,
'QA Engineer': 0,
'DevOps Engineer': 0,
'Project Manager': 0
};
let totalEffort = 0;
for (let task of tasks) {
resourceMap[task.requiredRole] += task.effortHours;
totalEffort += task.effortHours;
}
// Calculate FTE (Full Time Equivalent) needed
const fteMap = {};
for (let role in resourceMap) {
fteMap[role] = (resourceMap[role] / (projectDuration * 8 * 5)).toFixed(2);
}
return {
effortByRole: resourceMap,
fte: fteMap,
totalEffortHours: totalEffort,
totalWorkDays: totalEffort / 8,
costEstimate: this.calculateCost(fteMap)
};
}
calculateCost(fteMap) {
const dailyRates = {
'Senior Developer': 1200,
'Mid-Level Developer': 900,
'Junior Developer': 600,
'QA Engineer': 700,
'DevOps Engineer': 950,
'Project Manager': 800
};
let totalCost = 0;
const costByRole = {};
for (let role in fteMap) {
const fteDays = fteMap[role] * 250; // 250 working days/year
costByRole[role] = fteDays * dailyRates[role];
totalCost += costByRole[role];
}
return {
byRole: costByRole,
total: totalCost,
currency: 'USD'
};
}
}
5. Estimation Templates
## Project Estimation Summary
Project Name: [Project Name]
Date: [Date]
Estimator: [Name]
### Scope Summary
- Deliverables: [List key deliverables]
- Exclusions: [What's NOT included]
- Assumptions: [Key assumptions]
### Effort Estimation
| Phase | Effort (Days) | Resources | Notes |
|-------|---------------|-----------|-------|
| Planning | 5 | 1 PM | Requirement gathering |
| Design | 10 | 2 Architects | UI/UX & Technical |
| Development | 40 | 4 Devs | 5 features total |
| Testing | 15 | 2 QA | Manual + Automation |
| Deployment | 5 | 1 DevOps | Staging & Production |
| **Total** | **75 Days** | **Avg 3.0 FTE** | |
### Schedule Estimate
- Start Date: [Date]
- Duration: 15 weeks
- End Date: [Date]
- Critical Path: Development & Testing phases
### Risk & Contingency
- Risk Buffer: 20% (15 days)
- Optimistic: 12 weeks
- Most Likely: 15 weeks
- Pessimistic: 18 weeks
### Cost Estimate
- Labor: $125,000
- Infrastructure: $15,000
- Tools/Licenses: $5,000
- **Total**: $145,000
### Confidence Level
- Estimation Confidence: 80% (Medium-High)
- Key Uncertainties: Third-party integrations
Best Practices
✅ DO
- Use multiple estimation techniques and compare results
- Include contingency buffers (15-25% for new projects)
- Base estimates on historical data from similar projects
- Break down large efforts into smaller components
- Get input from team members doing the actual work
- Document assumptions and exclusions clearly
- Review and adjust estimates regularly
- Track actual vs. estimated metrics for improvement
- Include non-development tasks (planning, testing, deployment)
- Account for learning curve on unfamiliar technologies
❌ DON’T
- Estimate without clear scope definition
- Use unrealistic best-case scenarios
- Ignore historical project data
- Estimate under pressure to hit arbitrary targets
- Forget to include non-coding activities
- Use estimates as performance metrics for individuals
- Change estimates mid-project without clear reason
- Estimate without team input
- Ignore risks and contingencies
- Use one technique exclusively
Estimation Tips
- Add 20-30% buffer for unknown unknowns
- Review estimates weekly and adjust as needed
- Track estimation accuracy to improve future estimates
- Use estimation to identify scope issues early
- Communicate confidence level with stakeholders