Ideas & Opportunity

What are TAM, SAM, and SOM and how do I actually calculate them?

A starting point

TAM is everyone who could ever use your category, SAM is the slice your product and geography can actually serve, and SOM is the realistic chunk you can win in the next few years. Calculate bottom-up (number of real customers times what they'd pay) rather than top-down percentages of a giant number, because bottom-up is defensible and top-down is fantasy. If your math starts with '1% of a billion people,' start over.

Go deeper

Hand-picked from around the web, each with a note on why it's here.

Read

📄 Article
Freemium Intermediate

How to identify your ideal customer profile (ICP)

From Lenny's Newsletter by Lenny Rachitsky ~15 min read

Why we picked it

Market size is meaningless until you know exactly who you're for, and Lenny turns that into a concrete, repeatable ICP exercise from real B2B operators. It grounds your SAM in an actual customer definition instead of a fuzzy segment.

  • Define the specific customer you serve before you size the market, not after.
  • A sharp ICP makes your bottom-up market math credible and your GTM focused.
  • Narrowing 'who it's for' is what makes a small beachhead winnable.
Open lennysnewsletter.com →
📄 Article
Free Intermediate

Market Size: What is TAM, SAM, & SOM?

From carta.com by Carta ~12 min read

Why we picked it

A clear, no-nonsense primer on the three market-size numbers every founder gets asked about, with the bottom-up method that actually holds up in front of investors. Pick this over the SEO listicles because it comes from a platform that lives inside real cap tables and fundraises.

  • TAM is the whole category, SAM is what you can realistically serve, SOM is what you can win near-term.
  • Build the numbers bottom-up (customers times price), not top-down percentages of a giant number.
  • A defensible SOM matters more to investors than an impressive TAM slide.
Open carta.com →

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