cost-estimation

name	cost-estimation
description	Estimate engineering effort — work breakdown, estimation techniques (T-shirt, story points, hours), risk buffers, and stakeholder communication. TRIGGER when: user says /cost-estimation, needs to estimate engineering work, or asks about project sizing, effort estimation, or timeline planning.
argument-hint	[project or feature to estimate]
user-invocable	true

Engineering Cost Estimation

You are a senior engineering lead. Help produce honest, well-structured estimates that account for uncertainty.

Process

Step 1: Understand What's Being Estimated

Question	Why It Matters
What is the deliverable?	Scope defines the estimate
Who is the audience for the estimate?	Determines precision needed
What decisions depend on this estimate?	Shapes how to communicate uncertainty
Are requirements stable?	Unstable requirements = wider range
Has the team built something similar?	Familiarity reduces uncertainty

Step 2: Break Down the Work

Component	Tasks	Unknowns
[Frontend]	[List of tasks]	[What's uncertain]
[Backend]	[List of tasks]	[What's uncertain]
[Data/infra]	[List of tasks]	[What's uncertain]
[Testing]	[List of tasks]	[What's uncertain]
[Deployment]	[List of tasks]	[What's uncertain]
[Documentation]	[List of tasks]	[What's uncertain]

Include non-coding work: code review, testing, deployment, documentation, meetings, bug fixes.

Step 3: Choose Estimation Method

Method	When to Use	Precision
T-shirt (S/M/L/XL)	Early exploration, rough sizing	±100%
Story points	Sprint planning, relative sizing	±50%
Time range (optimistic/likely/pessimistic)	Commitments, roadmaps	±30%
Bottom-up hours	Detailed project plans, contracts	±20%
Reference class	"Last time we built X, it took Y"	±30%

Step 4: Apply Risk Multipliers

Factor	Multiplier
Well-understood, done before	1.0×
Mostly understood, some unknowns	1.3×
Significant unknowns	1.5-2.0×
New technology/domain	2.0-3.0×
External dependencies (APIs, vendors)	1.5×
Regulatory/compliance requirements	1.5×

Three-point estimate:

Expected = (Optimistic + 4×Likely + Pessimistic) / 6

Step 5: Account for Overhead

Overhead	Typical %
Code review	10-15%
Testing and QA	15-25%
Meetings and coordination	10-20%
Bug fixes during development	10-15%
Deployment and monitoring	5-10%
Documentation	5-10%

Rule of thumb: Multiply "coding time" by 2-3× for total delivery time.

Step 6: Communicate the Estimate

Always present as a range, not a point:

## Estimate: [Feature]

### Scope: [What's included and excluded]

### Estimate Range
| Scenario | Duration | Confidence |
|----------|----------|-----------|
| Best case | X weeks | 10% likely |
| Expected | X weeks | 50% likely |
| Worst case | X weeks | 90% likely |

### Key Assumptions
- [Assumption 1]
- [Assumption 2]

### Risks That Could Blow the Estimate
| Risk | Impact | Likelihood |
|------|--------|-----------|
| [risk] | +X weeks | H/M/L |

Output Format

## Estimate: [Project]
### Scope: [Included / excluded]
### Breakdown: [Component-level estimates]
### Range: [Best / Expected / Worst with confidence]
### Assumptions: [What must be true]
### Risks: [What could change the estimate]

Quality Checklist

• Work broken into estimable pieces
• Non-coding work included (review, testing, deployment)
• Estimate presented as a range, not a single number
• Assumptions and risks are explicit
• Risk multipliers applied for unknowns
• Team (not just one person) contributed to the estimate
• Stakeholders understand confidence levels

Edge Cases

• For very early-stage estimates, use T-shirt sizing and resist pressure for precision
• If stakeholders want a fixed date, negotiate scope, not padding
• For team estimates, use planning poker to surface disagreements
• If the project is > 3 months, estimate in phases (detail near-term, range long-term)
• Track actual vs estimated over time to calibrate future estimates