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project-sizing-guide

Generates software effort estimates using PERT, T-shirt sizing, and Function Point Analysis.

4.6k|462|Updated Jun 21, 2025
Search Tags:#effort estimation#work breakdown structure#pert#t-shirt sizing#Sprint Planning#Project management#function point analysis
One-click install
npx skills add https://github.com/zebbern/claude-code-guide --skill project-sizing-guide
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: project-sizing-guide
Source: https://github.com/zebbern/claude-code-guide/tree/main/skills/project-sizing-guide
Command: npx skills add https://github.com/zebbern/claude-code-guide --skill project-sizing-guide

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes scripts (resource) components.

What problem does it solve?

Estimating how long a software feature or project will take is notoriously unreliable when done by gut feeling. This Skill produces structured, defensible effort estimates with confidence intervals, so teams can plan sprints, budget projects, and prepare external quotes on a quantitative basis.

Core Features & Use Cases

  • Three-Point Estimation (PERT): Computes expected effort, standard deviation, and 68%/90%/95%/99.7% confidence intervals from optimistic, most-likely, and pessimistic values per work package.
  • T-shirt Sizing: Maps XS–XXL sizes to person-day ranges and converts them into three-point estimates for finer-grained planning.
  • Function Point Analysis (FPA): Counts ILF, EIF, EI, EO, and EQ components with complexity weights, then converts function points to person-hours using technology-stack benchmarks plus risk buffers.
  • Use Case: A product manager asks how long a payment module will take. The Skill breaks the work into a WBS, applies PERT via the bundled calculator script, and returns a report with total expected effort, confidence intervals, and risk alerts.

Quick Start

Ask the agent to estimate the effort for your feature description using the project-sizing-guide, for example by providing a task list with optimistic, most-likely, and pessimistic person-day values.

Frequently Asked Questions about project-sizing-guide

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I estimate software project effort with three-point estimation?▼

Three-point estimation assigns optimistic (O), most-likely (M), and pessimistic (P) values to each work package, then computes expected effort as (O + 4M + P) / 6 and standard deviation as (P - O) / 6. The included calculator script aggregates these across tasks and outputs confidence intervals.

What is the difference between PERT, T-shirt sizing, and Function Point Analysis?▼

T-shirt sizing gives quick order-of-magnitude estimates for early feasibility studies. PERT provides per-task expected values with confidence intervals suited to sprint planning. FPA is the most rigorous method, counting function components for contract bidding and large-project RFPs.

How do I convert T-shirt sizes to person-days?▼

Each size maps to a person-day range: XS is 0.25-0.5, S is 0.5-2, M is 2-5, L is 5-15, XL is 15-40, and XXL is 40+. The calculator script converts sizes into O/M/P values and runs PERT aggregation automatically.

How many person-hours per function point should I use in FPA?▼

Industry benchmarks range from 4-8 hours per function point for low-code stacks, 8-12 for Python/JavaScript web development, 10-15 for Java/C# enterprise work, and 15-25 for embedded C/C++. Add a 15-30% management and risk buffer on top.

When should I not use Function Point Analysis?▼

FPA is excessive for early-stage feasibility checks where little detail is known; T-shirt sizing fits better there. It also requires enough requirement clarity to identify ILF, EIF, EI, EO, and EQ components, so vague requirements should be clarified first.

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