Serviceable Obtainable Market

What Serviceable Obtainable Market means in practice

SOM is the only one of the three market figures that should influence your actual plan. TAM tells you whether the category is big enough to bother with; SAM tells you what your model can reach; SOM tells you what you can realistically win with the resources you have, against the competitors already there.

It is grounded in capacity rather than ambition. If your channel can generate 40 qualified conversations a month and you close a quarter of them, your first-year customer count is arithmetic, not aspiration. Working forward from real channel throughput produces a number you can staff and budget against.

SOM is where honest founders and optimistic ones visibly diverge. Assuming a few percent of SAM "because the market is huge" is a red flag to anyone who has tried to acquire customers. Deriving SOM from channel capacity and conversion rates you can point to is the credible alternative.

How it is calculated

Worked example

Year-one target for the accounting-compliance product, from a £7.1m SAM.

• One working channel: partnership webinars, producing ~35 qualified conversations per month.
• Observed close rate on qualified conversations: 20% → 7 new customers per month.
• Allowing for ramp-up, roughly 60 customers in year one.
• SOM = 60 × £3,600 = £216,000 of annual recurring revenue.

Takeaway: £216k is about 3% of SAM — and because it was derived from channel capacity rather than assumed as a percentage, it doubles as a staffing and budget plan.

Common mistakes

• Picking a round percentage of SAM and presenting it as SOM. It is the least credible number in any plan.
• Ignoring competitors who already hold the customers you are counting.
• Assuming channel throughput scales linearly with spend — most channels saturate.
• Setting SOM over a vague horizon. Without a stated period the figure means nothing.

Related tool: TAM/SAM/SOM calculator.

Related terms

• Serviceable Addressable Market — Serviceable addressable market (SAM) is the portion of total addressable market you could actually sell to given your business model, geography, language, regulation and target segment — TAM minus everyone you structurally cannot serve.
• Total Addressable Market — Total addressable market (TAM) is the total annual revenue available if a product achieved 100% market share of everyone who could conceivably buy it — the theoretical ceiling, not a realistic target.
• Customer Acquisition Cost — Customer acquisition cost (CAC) is the total sales and marketing spend required to win one new paying customer, calculated by dividing all acquisition costs in a period by the number of customers acquired in that period.

Last reviewed 8 August 2026