What is Total Addressable Market (TAM)?
Definition: The total revenue opportunity available if a product achieved 100% market share, calculated by identifying every potential customer and multiplying by the average annual contract value.
TAM quantifies the size of your opportunity. If every company that could buy your product did buy it, how much revenue would you generate? It's a theoretical ceiling, not a forecast, but it anchors strategic decisions about which markets to pursue and how much to invest in go-to-market.
For GTM Engineers, TAM matters at the operational level. Your enrichment workflow needs to produce a list of companies that fit the ICP. The size of that list relative to your TAM determines whether you need to cast a wide net (large TAM, aggressive outbound) or focus narrowly (small TAM, account-based approach).
Calculating TAM: start with a market definition (e.g., "B2B SaaS companies with 50-500 employees in North America"). Count the companies (you can get this from Apollo, ZoomInfo, or LinkedIn Sales Navigator searches). Multiply by your average contract value. If there are 15,000 companies in your ICP and your ACV is $30K, your TAM is $450M.
Related metrics: SAM (Serviceable Addressable Market, the portion you can realistically reach) and SOM (Serviceable Obtainable Market, what you can win given competition). VCs care about TAM. GTM Engineers care about SAM and SOM because those numbers determine outbound volume, territory sizing, and pipeline targets.