Total Addressable Market (TAM) describes the potential demand within a defined market. Express it as a count of eligible buyers and, when estimating its financial size, the revenue opportunity for a stated period. It is an opportunity estimate, not a forecast of what your company will win.
State what you are counting
The iBD Our Market Worksheet begins with explicit market boundaries and a supported account count. Identify the primary customer group within that population. Other suitable groups need not match every ideal-profile condition. Identify the offer, geography, customer criteria, source and as-of date. Use a consistent unit: companies, locations and individual buyers are different counts.
To estimate annual revenue opportunity, multiply the eligible buyer count by supported annual spending on the relevant offer. Do not use those buyers’ total company revenues as if they were spending that amount with you. Avoid counting the same buyer repeatedly when segments overlap.
In a hypothetical market, 2,000 eligible companies each spending $10,000 a year on the relevant service represent a $20 million annual opportunity. Serving 100 such customers for a full year at that annual spending level would produce $1 million revenue on those assumptions. Winning them partway through the year requires a timing adjustment in the forecast.
Separate the broad market from the part you can pursue
External market-size discussions distinguish three scopes, as summarized in Amazon’s market-sizing guide:
- TAM: the full opportunity within the stated category and boundaries.
- Serviceable available market (SAM): the part your offering and reach can serve.
- Serviceable obtainable market (SOM): the portion you can reasonably expect to win within a stated period and plan.
The iBD worksheet uses “TAM” for its defined, filtered customer market. Record those boundaries so it can be compared honestly with a broader industry estimate. A large category statistic does not establish your addressable customer count or attainable revenue.
Sub-market tiering
Optional tiering groups the defined market by fit, such as ideal, strong and opportunistic. Use as many meaningful groups as the decision needs; three tiers are not a completion requirement. Write the filters and engagement rule for each group. Counts must reconcile without overlap. This customer-fit tiering is separate from the three approaches used to build the annual budget.
The tiers help prioritize work; they do not prove that every ideal customer will buy or that every lower-fit customer will lose money. Test fit against buying evidence, delivery requirements and economics.
Use sources, then test the commercial assumptions
Keep the source and date behind the count, and identify estimated inputs. Public business statistics, industry sources and customer research can support the work. AI can organize the research, but a cited answer still needs its underlying source checked. The U.S. Small Business Administration’s market-research guidance distinguishes demand, market size and competitive conditions.
Carry the chosen market, pricing and penetration assumptions into the Strategic Plan and financial forecast. Market size alone does not establish the cash flow or wealth required by the Owner’s Scorecard.
Put the idea to work
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