TAM, SAM, and SOM for medical devices
Three numbers show up in almost every device pitch deck. This guide explains what each one means, how to build them, and what an investor will ask when they look closely.
What TAM, SAM, and SOM mean
TAM, SAM, and SOM describe three nested slices of a market. Each one is smaller than the last, and each answers a different question.
TAM, the total addressable market, is the revenue available if every possible buyer of your type of product bought it. It answers how big the category is.
SAM, the serviceable addressable market, is the part of the TAM your product can actually serve given its indication, the care settings it fits, the geographies you will sell in, and whether the buyers can pay for it. It answers how much of the category is reachable by this product.
SOM, the serviceable obtainable market, is the share of the SAM you can realistically win in a stated period, given your sales capacity, competition, and adoption speed. It answers what you can plausibly capture.
The SOM is the number that should connect to your revenue plan. The TAM and SAM give it context.
Top-down and bottom-up sizing
Top-down sizing starts from a large published figure, such as total spending in a device category, and narrows it with percentages. It is fast, and it is easy to challenge, because the percentages are often guesses and the starting figure may be defined differently from your product.
Bottom-up sizing starts from units. You count the buyers or patients, estimate how many units each would use, and multiply by a price. Every input can be traced to a source or labeled as an assumption, which is why investors tend to trust it more.
Most careful work uses both. Build bottom-up first, then run a top-down check. If the two land within a reasonable range of each other, the estimate is more credible. If they are far apart, find out why before anyone else does. Our guide on how to size a market for a new device walks through the bottom-up steps in order.
How to define serviceable segments for a device
The step between TAM and SAM is where most of the judgment sits. For a medical device, these are the usual filters.
- Indication. The condition or use the product is intended for, and the patient group within it. A narrower intended use means a smaller SAM, and it should match how the product will actually be described.
- Care setting. Hospitals, outpatient clinics, physician offices, home care, and long-term care buy differently and have different budgets and decision makers.
- Geography. A market you cannot yet sell into does not belong in the SAM. Regulatory status by country is usually the deciding factor, and regulatory professionals should confirm it.
- Reimbursement and payer access. If a product depends on being paid for by an insurer or a health system, buyers without a payment route may not be serviceable, at least for now. Coverage and payment rules differ by market and change over time.
- Channel and buyer access. Some segments are reached through distributors, group purchasing, or direct sales, and your plan may cover only some of them.
Write down each filter and the source behind it. A SAM defined by named filters is much easier to defend than a single percentage.
A simple hypothetical example
These numbers are hypothetical and chosen only to make the arithmetic easy to follow. They do not describe any real product or market.
Imagine a device used in outpatient clinics in one country. Suppose there are 20,000 such clinics, each would buy 5 units, and the unit price is $2,000.
| Layer | Assumption | Result |
|---|---|---|
| TAM | 20,000 clinics x 5 units x $2,000 | $200 million |
| SAM | 40% of clinics fit the indication and have a payment route, so 8,000 clinics x 5 x $2,000 | $80 million |
| SOM | 5% of those 8,000 clinics by year five, so 400 clinics x 5 x $2,000 | $4 million |
Each row has an input someone can check. The 40% would need a source, such as a count of clinics offering the relevant service. The 5% would need support from a sales plan, for example how many clinics a sales team can reach and convert in a year. If those inputs change, the output changes in a way anyone can follow.
Common mistakes
A circular TAM defines the market by the product. If the TAM is the number of units you hope to sell, multiplied by your price, it says nothing about the market. Start from buyers or patients who exist independently of your plan.
Using total category spending as the SOM is another frequent error. A figure like "the market is $5 billion" describes the TAM at best. The SOM is what you can win with your team, funding, and timeline.
Other problems appear often enough to list.
- Applying a round percentage, such as "we only need 1%," with no link to how sales happen.
- Counting patients when the buyer is a facility, or the reverse, so the unit and the price do not match.
- Mixing device revenue with the revenue of the whole care pathway.
- Ignoring price erosion, discounts, and channel margins, so revenue per unit is overstated.
- Using a source whose category definition differs from your product, without saying so.
What to document so the sizing holds up
Investors rarely accept a market size on trust. They ask where each input came from and what happens if it is wrong. Keeping the following in one place makes those conversations short.
- The unit of count and why it matches the buyer.
- A source and date for every input, or a clear label that it is an assumption.
- The filters that take you from TAM to SAM, each with its reasoning.
- The sales and adoption logic behind the SOM.
- A top-down cross-check, and an explanation of any gap.
- A sensitivity range showing which two or three inputs move the answer most.
This is the structure we use in market sizing for startups, and the Growth package on our services page includes TAM, SAM, and SOM with documented sources and assumptions. Our independent samples show how this looks in a finished report. Sizing is research and analysis, not investment advice, and the decisions that follow from it are yours. To talk through your own case, book a discovery call.
Common questions
Is SOM the same as a revenue forecast?
Should TAM be global or limited to one country?
Do investors expect both top-down and bottom-up sizing?
Does reimbursement belong in the SAM?
Related
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