For consultants sizing a client's market
TAM SAM SOM Calculator With Sourced Figures
Your client's TAM, SAM and SOM: the market sized top-down and bottom-up, with every figure traced to its source or flagged to check.
Free to start. No card needed.
How to calculate TAM, SAM and SOM by hand
TAM, SAM and SOM are nested yearly revenue figures for the whole market, the part your client can serve, and the share it can realistically win. Build them bottom-up first: count the buyers and multiply by what one pays a year. Count the unit that actually buys. The Census Bureau's County Business Patterns counts establishments, each a single physical location1, so a 40-store chain is 40 establishments but may be one buyer. For firm counts, the Bureau publishes Statistics of U.S. Businesses2.
Take an invented client launching nurse-scheduling software at $36,000 a year per hospital. The American Hospital Association (AHA) counts 5,121 community hospitals3 in its 2024 survey, so TAM is 5,121 × $36,000, about $184 million. It can serve only the 1,797 rural ones for now, so SAM is about $65 million. Build SOM from capacity, not a share of SAM. Two salespeople closing 12 hospitals a year each win 72 in three years, a SOM of $2.6 million a year before churn.
Then check top-down, narrowing a published total by region, segment and product. Say the client's board pack sizes hospital workforce software at $1.2 billion, and you estimate nurse scheduling at a quarter: $300 million. At $36,000 a year, that implies 8,333 buyers, more than the 6,100 hospitals the AHA counts in the whole US. Y Combinator's Michael Seibel prefers bottom-up because it helps you avoid this common top-down pitfall: not narrowing down the customer enough4. Explain the gap rather than averaging, then vary each assumption to see which moves SOM most.
How it works
How River calculates TAM, SAM and SOM
Start with a few lines on what the client sells, to whom, where and at what price. Or drop up to 10 files, such as a pitch deck, business plan or your notes. River reads all of it before it researches anything. Then it looks up the public figures the sizing needs, such as buyer counts from a statistics office or trade association. It opens each page and copies the figure exactly, with its year and what it covers.
A calculator that multiplies the numbers you type is only as good as your guesses, so River shows where each figure came from. Public figures are linked, figures from your material are marked "from your notes" with the file and page, and anything unsourced is marked "(estimate, to check)" with its reasoning. It never fills a gap with a statistic it can't show you. Where it can open a published total, it sizes the market top-down as well as bottom-up and explains the gap.
Use it when a client asks how big an opportunity is: a new segment, a new region, a product launch or a plan going to investors. If that question sits inside a bigger strategy problem, break it down first with the issue tree template, and test the client's position with the SWOT analysis generator. Once the sizing is done, River can write the market slide, and the action title generator can sharpen its headline.
How it works
From a client brief to TAM, SAM and SOM
Paste or drop
Paste what the client sells, to whom and where, or drop the pitch deck or business plan.
River finds the figures
It reads everything first, then looks up public counts and totals and opens every source it cites.
Get your sizing
Top-down and bottom-up tables, SAM and SOM logic and a sanity check land in a doc in your free workspace.
Test the assumptions
Change a figure and ask River to rerun the numbers, or turn the sizing into a market slide.
| Layer | Calculation | Size | Source |
|---|---|---|---|
| TAM | 5,121 community hospitals × $36,000 | $184.4M | AHA Fast Facts 2026 · your notes |
| SAM | 1,797 rural hospitals × $36,000 | $64.7M | AHA Fast Facts 2026 |
| SOM, year 3 | 72 hospitals × $36,000 | $2.6M | Your notes: 2 sellers × 12 a year |
| Top-down check | $1.2B × 25% for nurse scheduling | $300M | Your notes · 25% is an estimate |
Top-down lands at 1.6 times the bottom-up TAM. Price per hospital moves the answer most.
What you'll get
TAM, SAM and SOM built two ways, with every figure sourced or flagged
- Top-down and bottom-up sizing tables side by side, with the gap explained
- Every assumption with its source: a public link, your notes, or marked to check
- SAM and SOM logic, and the three assumptions that move the answer most
Before and after
Your client's brief in. A market size you can defend.
Nurse-scheduling software for US hospitals, $36,000 a year per hospital. Launching with rural hospitals only, no customers yet. Two salespeople, each expected to close about 12 hospitals a year. The board pack says hospital workforce software is a $1.2 billion market, with no source.
Bottom-up. TAM: 5,121 community hospitals × $36,000 = $184.4M. Count: AHA Fast Facts 2026, linked. Price: from your notes. SAM: 1,797 rural community hospitals × $36,000 = $64.7M. Count: same source. SOM by year 3: 2 sellers × 12 hospitals × 3 years = 72 hospitals, or $2.6M a year, with no churn (estimate, to check). That is 4% of SAM. Top-down check. $1.2B hospital workforce software (from your notes, no source given) × 25% for nurse scheduling (estimate, to check) = $300M. Sanity check: top-down is 1.6 times the bottom-up TAM. $300M ÷ $36,000 implies 8,333 hospitals, more than the 6,100 AHA counts in the whole US. The 25% may be too high, or the total may cover more than US hospitals or assume a higher price per hospital. Moves SOM most: price per hospital, then hospitals closed per seller a year.
Each figure carries its source, so you know which ones to confirm before the client sees them.
What lands in your doc
What's in your market sizing
- Top-down and bottom-up sizing tables, with the calculation written out in every row
- SAM built one exclusion at a time, and SOM built year by year from the client's capacity
- An assumptions table that links each public figure, marks figures from your notes and flags estimates
- A sanity check that sets the two methods side by side and explains why they differ
- The three assumptions that move SOM most, each recalculated at a plausible low and high value
- A closing list of short questions for the client, covering the facts and estimates to check
Questions consultants ask
Common questions
What is TAM, SAM and SOM?
TAM, SAM and SOM stand for total addressable market, serviceable available market and serviceable obtainable market. TAM is the yearly revenue if every possible buyer bought the offer. SAM is the part the business can reach with its product, channels and geography. SOM is the share it can realistically win in a stated period, such as three years.
How do you calculate TAM, SAM and SOM?
Multiply the number of possible buyers by what one pays a year to get TAM. Keep only the buyers the business can serve today to get SAM. Build SOM from capacity: the customers its salespeople or partners can win and keep in a stated period, times the price. Then compare the result with a published total for the category and find out why the two differ.
What is the difference between top-down and bottom-up market sizing?
Top-down starts from a published total for the category and narrows it, while bottom-up counts buyers and multiplies by what each pays. Top-down inherits whatever the total chose to measure. In 2014, Uber investor Bill Gurley argued that sizing Uber from the historical taxi and limousine market5 assumed the future would look like the past. River builds both when it can open a published total, and explains the gap.
What is a realistic SOM?
One the business can explain from its own capacity. Start with today's customers, add those its sellers or partners can win each year, subtract likely churn, and multiply by the price. A round share of SAM, such as "we only need 1%", is a hope, not evidence. River shows SOM as a figure and as a share of SAM, with the year-by-year working.
How do I calculate TAM, SAM and SOM with River?
Type what the client sells, to whom and where in the box at the top of this page. Or drop up to 10 files, such as a pitch deck, business plan or notes, as Word, PDF, PowerPoint, Excel, CSV or text. River looks up the public figures and writes the sizing into a doc in your free River workspace, where you can edit it or ask for changes.
Is my client's business plan private?
Files you drop are kept in your own River workspace and shared only if you choose to. River's privacy policy says it doesn't use your documents to train AI models. The AI services that do the work receive only what they need, under data protection agreements that stop them training on it. If the plan is confidential, check your client agreement before you upload it.
Is the TAM SAM SOM calculator free?
Yes, it is free to start, with no card needed. Your market sizing opens in a River workspace, where you can edit it, share it with your team or ask River to change it. Paid plans add more AI use and access to the most advanced models.
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