TAM, SAM, SOM
Three concentric circles of market opportunity. Total Addressable Market (TAM) is everyone who could buy, Serviceable Addressable Market (SAM) is everyone you could reach, and Serviceable Obtainable Market (SOM) is what you can realistically capture.
TAM, SAM, SOM: From Fantasy to Reality
TAM is the dream. SAM is the opportunity. SOM is the plan. Every pitch deck has a TAM slide showing billions of dollars. Investors care more about your SOM — the slice you can realistically capture in the next 3-5 years. If your TAM is $10B but your SOM is $20M, your market size slide needs more work.
The Three Layers
TAM (Total Addressable Market): If every potential buyer on Earth purchased your product, how much revenue would that generate?
SAM (Serviceable Addressable Market): Of that total, which portion can you actually serve given your product, pricing, geography, and go-to-market?
SOM (Serviceable Obtainable Market): Of your SAM, what can you realistically capture given competition, sales capacity, and brand awareness?
The Bottom-Up Approach
Count potential customers, not market dollars. How many companies match your ICP? What percentage can you reach? What is your expected win rate? Multiply by your ACV. This produces a SOM grounded in reality rather than industry analyst projections.
When TAM Expands
The best SaaS companies expand their TAM over time by adding products, entering new segments, or moving upmarket. Snowflake started in data warehousing (smaller TAM) and expanded into data sharing, data science, and applications (much larger TAM). Your initial TAM is not your permanent ceiling.
Frequently Asked Questions
How do you calculate TAM for B2B SaaS?
Two approaches: top-down (industry reports and total market value) and bottom-up (number of potential customers x your ACV). Bottom-up is more credible because it is grounded in your actual pricing and target market. If there are 50,000 companies that fit your ICP and your average ACV is $20K, your TAM is $1B.
What is a good TAM for a VC-backed SaaS company?
VCs typically want to see a TAM of $1B+ to believe the company can reach $100M+ ARR. But TAM alone does not matter — what matters is your credible path to capturing a meaningful share. A $500M TAM where you have a clear path to 10% share is more compelling than a $10B TAM where your path is unclear.
