SOM (serviceable obtainable market) is the revenue you can plausibly win in the next planning horizon — the bottom of the TAM / SAM / SOM stack investors expect in pitch decks.

How it works

Start with TAM — total demand if you owned the category. Narrow to SAM — segments you can serve with current product and geography. SOM applies execution constraints: sales headcount, win rates, churn, and competitive share caps.

Example: a vertical SaaS vendor might show $20B TAM, $2B SAM in mid-market manufacturing, and $40M SOM over three years based on 200 target accounts at $200K ACV with realistic conversion.

Bottom-up SOM — accounts × price × attach rate — beats top-down percentages of giant TAM numbers in diligence.

Why it matters

• Founders: SOM grounds hiring and fundraising asks. Hitting SOM builds credibility for SAM expansion stories.
• Investors: They stress-test whether SOM supports venture returns at entry valuation — a huge TAM with tiny SOM can still be a great seed bet if expansion path is clear.

Common mistake

Labeling entire SAM as SOM without a sales and marketing plan — investors treat it as hand-waving.

Related ideas

• TAM
• Bottom-up TAM
• Beachhead market