A large market number can establish context. It cannot explain how your company will win customers. That requires a connection between the market you describe and the business you are actually building.
When that connection is missing, market sizing becomes a decorative slide. The useful question is not simply how much spending exists. It is which buyers you can serve, what they buy, and what has to happen before some of that spending becomes your revenue.
Give each market number a clear boundary
TAM, or total addressable market, describes the broader revenue opportunity for a defined product and customer need. SAM, or serviceable available market, narrows that opportunity to customers your offering and business model can serve. SOM, or serviceable obtainable market, estimates a realistic portion you could reach within a stated period.
The boundaries matter more than the acronyms. Geography, customer size, buying requirements, distribution, and product readiness can all reduce the market you can serve. Explain those limits instead of hiding them behind three increasingly smaller circles.
Build upward from identifiable customers
Consider an illustrative company selling scheduling software to independent clinics. It starts with a count of clinics in its target region, filters for the clinic types its product supports, and applies a stated annual price. Every input is a working assumption until supported by a reliable source or customer evidence.
The company should not use all healthcare technology spending as though it were available scheduling-software revenue. Nor should it combine a count of individual practitioners with a price charged per clinic. The customer unit, purchase unit, and revenue calculation need to agree.
A broader industry report can provide a reasonableness check, but it may define the market differently. Record that difference. Two attractive numbers do not validate each other when they measure different things.
Make the obtainable market fit your sales plan
“We only need one percent” skips the operating work. Estimate the customers you can plausibly reach through the channels you intend to use, the time a purchase takes, and the capacity available to sell, implement, and support the product.
For the clinic example, a limited implementation team might constrain early growth even when demand is strong. A longer buying process could delay revenue. Your obtainable-market estimate should acknowledge those constraints and state its time horizon.
Compare that estimate with your financial forecast. If the revenue plan requires more customers than your sales capacity can plausibly support, revise the assumptions or explain what investment changes that capacity. A market slide and a forecast should describe the same business.
Use a one-page market assumptions worksheet
Write down your target customer, geography, qualifying criteria, estimated customer count, expected annual revenue per customer, and planning period. Beside each input, record its source, date, and any limitation. Mark estimates clearly.
Next, list how customers will discover you, who authorizes the purchase, how long buying may take, and what onboarding requires. Identify the assumption that would most change your conclusion if it were wrong.
That last assumption is a research priority. Interview potential buyers, examine available market data, or test a channel before turning uncertainty into a confident percentage. Your goal is a market argument someone can follow and question productively.
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