TAM, SAM, SOM explained with a worked example

What the three layers mean

• TAM — total addressable market. Everyone in the world who could conceivably buy this category of product, at a realistic price. It answers: if everything went perfectly, how big could this ever get?
• SAM — serviceable available market. The slice of TAM your actual product can serve: your geography, language, price point, and delivery model. An English-only web app does not serve the whole world on day one.
• SOM — serviceable obtainable market. The share of SAM you can realistically win in the first two to three years, given competition and your distribution. This is the number your early revenue plan should be built on.

Why investors ask for all three

TAM proves the ceiling is high enough to matter. SAM proves you have a focused wedge rather than a vague "everyone" market. SOM proves you have thought about how you actually get customers. A huge TAM with no credible SOM is a dream; a credible SOM inside a tiny TAM is a lifestyle business — fine, but know which one you are building.

A worked example: a meal-planning app for diabetics

Say you are building a subscription meal-planning app for people with type 2 diabetes, launching in the US in English, at $10 per month ($120 per year).

• TAM. Roughly 38 million Americans have diabetes, and the large majority are type 2. If 30 million type 2 patients each spent $120 a year on meal-planning help, the category ceiling is about $3.6 billion a year. Source every input: CDC diabetes statistics for the patient count, your own price for the spend.
• SAM. Narrow to who you can actually serve: US adults with type 2 diabetes who own a smartphone and already pay for at least one health or food app. If published survey data suggests that is 20 percent of patients, SAM is about 6 million people, or $720 million a year at your price.
• SOM. What can you win in three years? If the category leader has a few hundred thousand paying users and you plan to reach 30,000 subscribers through content and partnerships, SOM is 30,000 × $120 = $3.6 million a year. That is a real business plan, not a percentage plucked from the air.

Top-down and bottom-up must agree

The example above is top-down: start from published statistics and narrow. Always cross-check bottom-up: count the actual buyers you can reach (search volume for the problem, community sizes, app-store category downloads) and multiply by your price. If the two methods disagree by more than an order of magnitude, one assumption is wrong — find it before an investor does. Our market sizing guide covers both methods in detail.

The mistakes that sink TAM slides

• Quoting an industry report's total as your TAM. "The global wellness market is $5 trillion" is not your TAM unless you sell all of wellness.
• The 1 percent fallacy. "We only need 1 percent of China" skips the entire question of how you win anyone at all.
• Unsourced filters. Every narrowing step from TAM to SAM needs a source or a stated, testable assumption.
• Static thinking. A small market growing 40 percent a year can be a better bet than a huge stagnant one — check the trend, not just the size.

Do it the fast way

Marketproof's evaluation runs this sizing for you: it looks up published statistics, applies the narrowing filters with citations attached to every number, and flags when top-down and bottom-up estimates disagree. Run a free evaluation on your idea, work through the full idea validation checklist, or map the players you will compete with using the competitor analysis template.