Metrics & Performance
Market Size Estimation
The process of quantifying the revenue opportunity for a product using TAM, SAM, and SOM frameworks.
Market size estimation quantifies the total revenue opportunity available to a product or service. The standard framework uses three nested circles: TAM (Total Addressable Market — entire market if you had 100% share), SAM (Serviceable Addressable Market — segment you can reach with your product), and SOM (Serviceable Obtainable Market — realistic near-term capture). Bottom-up analysis (unit economics × potential customers) is more credible than top-down (industry reports × assumed share).
In Practice
An HR tech startup estimates: TAM = all HR software spending ($40B), SAM = mid-market companies in North America ($8B), SOM = companies actively looking to replace legacy systems ($800M). Bottom-up: 50K target companies × $15K ACV = $750M SAM.
Why It Matters
Market size determines whether a venture-scale outcome is possible. VCs need to believe the market is large enough to produce a fund-returning exit from a single portfolio company.
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