TAM vs SAM vs ICP

These three terms get used almost interchangeably in casual conversation, but they answer different questions and sit at different zoom levels.

Term	Question it answers	Typical use
TAM (Total Addressable Market)	How many companies could theoretically ever buy this category of product?	Investor decks, market-sizing exercises
SAM (Serviceable Addressable Market)	Of that, how many can we actually reach and sell to given our go-to-market, geography, and language?	Planning which segments/regions to actually go after
ICP (Ideal Customer Profile)	Of the companies we can reach, which specific ones are the best fit and most likely to buy?	Building the actual target account list a rep works from

Why this matters more than it sounds

TAM is a sizing exercise, useful for a fundraise, mostly useless for a rep deciding who to call Tuesday morning. The mistake small teams make is skipping straight from TAM ("the whole market is worth billions") to a cold list, without the ICP step that actually narrows things to companies worth the effort.

A back-of-envelope TAM estimate for a small team

1. Pick the industry codes that match your ICP (e.g. specific NACE/SIC codes, not "software" broadly).
2. Estimate how many registered companies exist in those codes, within your target geography and size band. Business registries or a quick search of a company database usually gets you close enough.
3. That number is roughly your SAM. Your ICP is the subset of it you'd actually prioritize calling first.

For a walk-through with real numbers, see How Many Companies Actually Fit Your ICP?