# Project Sizing Guide

Software project effort estimation assistant.

- Repository: https://github.com/zebbern/claude-code-guide (4691 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: yes, review before use

## Install

Claude Code: `npx skills add zebbern/claude-code-guide --skill project-sizing-guide -g -a claude-code -y`
Codex: `npx skills add zebbern/claude-code-guide --skill project-sizing-guide -g -a codex -y`
Cursor: `npx skills add zebbern/claude-code-guide --skill project-sizing-guide -g -a cursor -y`
Gemini CLI: `npx skills add zebbern/claude-code-guide --skill project-sizing-guide -g -a gemini-cli -y`

## Description

Software project effort estimation assistant. Outputs three-point estimates (optimistic/most-likely/pessimistic values with confidence intervals), T-shirt sizes, or Function Point Analysis (FPA) counts. Triggered when users ask 'how long will this feature take,' need to assess project workload, perform PERT estimation, T-shirt sizing, FPA, sprint planning, or quote-based effort breakdowns.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Project Sizing Guide, Software Project Effort Estimation

Helps teams produce scientifically grounded effort estimates for software projects, based on three major methodologies: Three-Point Estimation (PERT), T-shirt Sizing, and Function Point Analysis (FPA). Outputs optimistic, most-likely, and pessimistic values along with risk intervals.

## Quick Start

1. **User provides a requirements description** → Agent identifies functional modules and breaks them into a Work Breakdown Structure (WBS)
2. **Select an estimation method** → Choose the best-fit approach based on project stage and available information
3. **Estimate each item** → Assign O/M/P (Optimistic / Most Likely / Pessimistic) values to every work package
4. **Aggregate and report** → Generate an estimation report with risk analysis and confidence intervals

A calculation helper is available:
```bash
python3 scripts/estimate_calculator.py --method pert --tasks '[{"name":"User Login","O":2,"M":3,"P":8}]'
```

---

## Method Selection Guide

| Scenario | Recommended Method | Rationale |
|----------|-------------------|-----------|
| Early feasibility study, rough budgeting | T-shirt Sizing | Little information available; quickly align on order of magnitude |
| Sprint planning, iteration estimation | Three-Point Estimation (PERT) | Good granularity with confidence intervals |
| Contract bidding, large-project RFPs | Function Point Analysis (FPA) | Most rigorous; industry-comparable |
| Team has historical data | PERT + historical calibration | Combines empirical correction with data |

---

## Method 1: Three-Point Estimation (PERT)

### Core Formulas

The rest: https://github.com/zebbern/claude-code-guide/blob/HEAD/skills/project-sizing-guide/SKILL.md