TAM SAM SOM

TAM (total addressable market) is the total revenue opportunity if every potential customer in the world bought your product. SAM (serviceable addressable market) is the portion of TAM you can realistically reach given your product, geography, and channels. SOM (serviceable obtainable market) is the share of SAM you can capture, usually framed over 3 to 5 years. Investors use the three figures together to size the opportunity and to test whether a founder thinks rigorously about market.

There are two ways to calculate these numbers and only one of them earns trust. Top-down sizing starts from a published industry figure ("the global CRM market is $90 billion, we will capture 1 percent") and is almost always how founders inflate TAM in pitch decks. Investors discount it on sight. Bottom-up sizing starts from the unit economics: number of target customers in your SAM, times average annual contract value, equals SAM revenue. A bottom-up SAM forces you to name your customer, your pricing, and your reachable channel, which is what makes the math defensible. The convention is to express all three as revenue per year, in the same currency, with the year (and any growth rate) stated. A widely cited rule of thumb in venture: a credible Series A typically requires a SAM in the billions and a SOM in the hundreds of millions over five years, with the assumptions written down.

Ryan's Take

Founders pad TAM because they think bigger numbers raise bigger rounds. Investors read the deck for 30 seconds and clock the move. A $1 trillion TAM tells me you Googled "global software market" and stopped thinking. A $400 million bottom-up SAM with a credible path to $50 million in SOM tells me you actually know who your customer is and what they pay. Smaller, defensible numbers beat huge, hand-wavy ones every time. Build the math from the customer up.

What founders get wrong: Reaching for the biggest possible TAM and reverse-engineering SAM and SOM to fit. The correct order is bottom-up: define your customer, your pricing, and your reachable market, then size up.

FAQ

What does TAM SAM SOM stand for?
TAM is total addressable market (the entire global opportunity), SAM is serviceable addressable market (the portion you can realistically reach), and SOM is serviceable obtainable market (the share you expect to capture, usually over 3 to 5 years).

How do you calculate TAM SAM SOM?
Bottom-up: start with the number of target customers in your reachable market, multiply by average annual contract value, and that is your SAM revenue. SOM is the share of SAM you expect to capture. TAM extends the same logic globally.

What is the difference between top-down and bottom-up market sizing?
Top-down starts from a published industry total and applies a small percentage ("we capture 1 percent of $90B"). Bottom-up starts from the customer ("X customers at Y price equals Z revenue"). Investors trust bottom-up.

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