Calculate TAM/SAM/SOM for startup market sizing

This skill generates a comprehensive market opportunity analysis for a startup, including Total Addressable Market (TAM), Serviceable Available Market (SAM) and Serviceable Obtainable Market (SOM) calculations, using both bottom-up and top-down methodologies. It works as an interactive market sizing command that defines the target market, gathers data, calculates TAM bottom-up, validates it top-down, narrows to SAM, estimates a realistic 3 to 5 year SOM and presents the findings in a formatted report. It references a companion market-sizing-analysis skill for frameworks, industry templates and data source recommendations.

The steps:

• Gather context by asking for the product or service and the problem it solves, the target customers (industry, size, geography), the business model and pricing, the company stage (pre-launch, seed or Series A) and the initial geography.
• Bottom-up TAM by business type. For B2B and SaaS, define customer segments, estimate the number of companies in each, determine average contract value and sum segment size times ACV. For consumer and marketplace, estimate addressable users and multiply by average revenue per user and frequency. For transactions and e-commerce, estimate gross merchandise volume and multiply by the take rate or margin.
• Gather market data with web search, citing every source with URL and publication date and documenting assumptions. Recommended sources are government data such as Census and BLS, industry reports such as Gartner, Forrester and Statista, public company filings, trade associations and academic research.
• Top-down validation: find the total category size, apply geographic and segment filters and compare to the bottom-up TAM, which should be within 30 percent. If the variance is larger, investigate and explain it.
• SAM: narrow TAM with realistic filters for geography, product capability, market readiness and addressable switching.

SAM = TAM × Geographic % × Product Fit % × Market Readiness %

• SOM: a conservative approach is recommended, at 2 to 3 percent of SAM in year 3 and 4 to 6 percent in year 5, considering competitive intensity, available resources, go-to-market effectiveness and differentiation strength.
• Report: a nine-section markdown report covering an executive summary, market definition, bottom-up analysis, top-down validation, SAM calculation, SOM projection with customer counts and revenue, market growth (CAGR and drivers), validation and sanity checks such as public company comparisons, and an investment thesis with positives, risks and next steps. The skill offers to save it as market-opportunity-analysis-YYYY-MM-DD.md and confirms the location.

Use it when working on market opportunity analysis for a startup or needing guidance, best practices or checklists for market sizing. Do not use it when the task is unrelated to market opportunity analysis or needs a different domain or tool. Its output is not a substitute for expert review. Thorough sizing typically takes 30 to 60 minutes, quality depends on data availability so limitations should be explained, and results should be updated annually. If required inputs, permissions or success criteria are missing, it stops and asks for clarification.

Inputs are the answers to the context questions. For example, an analysis of AI-powered email marketing for e-commerce companies with $1M or more in annual revenue in North America and a subscription of $50 to $500 a month. The output is the sized market with sources and assumptions, and the saved report. Best practices are to start bottom-up as the most credible approach, always triangulate with top-down, cite sources, document every assumption, be conservative on SOM, compare to public company benchmarks and explain data gaps. Avoid relying only on top-down, cherry-picking optimistic data, claiming more than 10 percent SOM without strong justification, mixing methodologies inappropriately, ignoring competition or skipping validation.

It uses web search and the file-writing tool, and pairs with /financial-projections, which uses SOM to build a revenue model, and /business-case, which includes the market sizing. Detailed examples are in a resources/implementation-playbook.md file.

Founders, startup analysts and investors who need a defensible, sourced TAM, SAM and SOM estimate and a venture-scale opportunity assessment.