TAM, SAM and SOM: how to calculate your total addressable market
Updated By the SalesOne research team9 min read
The short answer
TAM, SAM and SOM size a market in three steps. TAM (total addressable market) is all the demand for what you sell; SAM (serviceable addressable market) is the part you can serve; SOM (serviceable obtainable market) is the part you can realistically win soon. In B2B, count each in accounts first, then multiply by revenue per account.
What are TAM, SAM and SOM?
TAM, SAM and SOM are three nested sizes of a market: everything you could sell, what you can serve, and what you can win in the next year or two.
| Measure | The question it answers | How to count it in B2B |
|---|---|---|
| TAM: total addressable market | If every company that could use this bought it, how big is the market? | Every company with the problem you solve, in every market, times revenue per account |
| SAM: serviceable addressable market | How much of that can we actually serve today? | The companies in the regions, sizes and industries your offer and team can serve |
| SOM: serviceable obtainable market | How much can we realistically win soon? | The share of SAM your sales capacity and win rate can reach in one to two years |
Investors read TAM as ambition and SOM as credibility. A sales team needs the opposite order: SOM tells you how many accounts to work this year, and SAM tells you how long the list lasts.
How do you calculate total addressable market?
Calculate TAM bottom-up when you can: count the companies that fit, then multiply by what one of them pays you a year. Top-down estimates from industry reports are a cross-check, not a plan.
| Method | How it works | Use it when | Weakness |
|---|---|---|---|
| Bottom-up | Count companies that fit your profile, multiply by annual revenue per account | You sell to identifiable companies, as in most B2B | Needs a clear profile and a reliable count |
| Top-down | Take an industry report’s market size and apply a share | You need a quick outside check | The report’s market rarely matches your offer |
| Value-based | Estimate what the problem costs each customer and what share of that they would pay | Your offer creates a new category | Rests on assumptions you must test |
The bottom-up formula is simple: TAM = number of companies that fit × average annual revenue per company. Its value comes from the count, because every company in it can later become a row on your target account list.
How do you calculate TAM bottom-up, step by step?
Define the account in rules, count the companies that meet them from an official or reliable source, narrow to what you can serve, then multiply by revenue per account.
- Write your ideal customer profile as checkable rules: industry codes, size band, ownership and location.
- Count the companies that match. In the US, the Census Bureau’s County Business Patterns publishes the number of establishments with paid employees by industry and employment size each year; other countries publish similar business statistics. Remember that establishments are sites, not companies; the Census Bureau’s Statistics of US Businesses counts firms as well as establishments, by enterprise size.
- Apply the rules a statistic cannot: ownership, what the company actually makes, and exclusions such as subsidiaries that buy through a parent. Our guide to firmographics covers which fields to use.
- Multiply the remaining count by your average annual revenue per account. That is your SAM if the rules match what you serve today.
- Estimate SOM from capacity: accounts your team can work in a year × the share that become customers.
What does a TAM, SAM and SOM calculation look like?
Here is a bottom-up example for an engineering firm that sells plant-layout studies to metal manufacturers. Every number is fictional and only shows the method.
| Step | Accounts | Revenue per account a year | Market |
|---|---|---|---|
| TAM: metal manufacturers in the countries it could ever serve | 12,000 | $40,000 | $480 million |
| SAM: 100 to 1,000 employees, privately owned, within a day’s travel | 1,500 | $40,000 | $60 million |
| Accounts in SAM with a dated reason to act this year, such as a new plant or new operations leader | 300 | $40,000 | $12 million |
| SOM: what a team of three can work and win in a year (300 accounts × 8%) | 24 | $40,000 | $0.96 million |
The third row is the one most market sizing skips. Not every company in the SAM is ready to buy this year. Counting the ones with a dated reason, such as an expansion or a new leader, turns a market size into a work plan; that is the idea behind signal-based selling.
What is a realistic SOM?
A realistic SOM is set by sales capacity, not by a percentage of the market: the accounts your team can work well in a year, multiplied by the share that become customers.
| If | Your SOM is limited by | To grow it |
|---|---|---|
| Your SAM has more accounts than the team can work | Sales capacity | Focus on accounts with a dated reason now, or add capacity |
| The team runs out of accounts before the year ends | The size of your SAM | Widen the profile carefully, or add a new segment |
| Many accounts are worked but few become customers | Win rate | Improve timing and reach more of each buying group |
What mistakes make a TAM useless?
A TAM is useless when it cannot be turned into a list of companies: a top-down figure, a count of the wrong unit, or a market nobody on the team can actually sell to.
- Quoting an industry report’s market size as your TAM.
- Counting sites as companies, which double-counts multi-site firms.
- Sizing in dollars only, with no count of accounts behind it.
- Including segments you cannot serve today in SAM.
- Treating the whole SAM as ready to buy this year.
- Never updating it. Companies open, close, merge and change owners every year.
How do you turn a TAM into a target account list?
Turn the SAM count into named companies, check each against your profile with a source, and keep the ones with a dated reason to act now at the top of the list.
A bottom-up TAM is already most of the way to a list. Name the companies behind the count, record why each is kept or turned down, and look for the events that make the problem you solve urgent. Our guide on how to build a target account list walks through it, and account qualification covers the keep-or-reject decision.
How does SalesOne work from your market size?
SalesOne is AI account research and qualification for B2B teams. You set the profile once in the ICP step; S1 agents then search the market for companies that fit, record each buying signal with its source and date, and keep or reject every company with a reason.
In SalesOne’s production research runs in October 2026, 249 of 1,051 companies checked were kept; about three in four were turned down, each with its reason. That is the third row of the example above, done for your own market.