TAM · SAM · SOM
Total Addressable Market / Serviceable Available Market / Serviceable Obtainable Market
What is TAM?
- A framework for sizing a market in three narrowing steps
- TAM (total) → SAM (serviceable) → SOM (obtainable)
- Present both an upper bound (potential) and a lower bound (target)
Adopting TAM, SAM, and SOM changes the conversation in the room. A claim like 'this market is big' becomes the question 'By what criteria, and where did you draw the line?' The real payoff of this framework is not a bigger number but moving the assumptions behind the number out of the spreadsheet so they can be checked. Business units, finance, and investors who used to quote different sizes for the same market end up with a shared question: how much does the number move if one assumption changes?
There are two main ways to size a market. Top-down starts from total spending in industry statistics or trade-association data and cuts it down with industry, size, and region filters. Bottom-up builds up by multiplying the number of target companies by average contract value and purchase frequency. If the two results differ by more than 2x, one of the assumptions is wrong, and you must find out which. Units must also be consistent. Define TAM as annual spending (KRW per year), not a number of companies, and attach a reference year to SOM, such as "as of year 3," so cumulative and single-year figures don't get mixed.
In B2B, the filters that narrow SAM are your ICP. These include employee count, equipment and system compatibility, the purchasing decision-making unit, and the regions your engineers can cover. If you attach one line of supporting evidence to each filter, you won't have to dig through source material again when you defend the number later. The market-share assumption behind SOM should also be explained through your own capacity, such as '3 competitors and the number of inquiries 4 sales reps can handle per year'.
The most common misstep in practice is turning SOM into a sales target. SOM is a realistic upper-bound estimate; if you pass it straight down as a team KPI, then when the market assumptions miss, accountability falls on sales alone. The "what if we just win 1%" calculation is risky, too. If you can't explain whose business that 1% would come from, you'll fall apart on the first question in an investment review. Teams also often leave a market-size analysis untouched for two to three years, and keep burning headcount and budget without noticing that SAM itself has shrunk because of new competitors or regulatory change.
John KimInstructor John Kim, author of “B2B Marketing Design” and CEO of Nanum Consulting
Kwangdong MinExpert in business models, revenue models, and market research| Category | TAM | SAM | SOM |
|---|---|---|---|
| Meaning | Total Addressable Market | Serviceable market | Obtainable Market |
| Scope | Theoretical maximum | Reachable | Realistically capturable |
| Criteria | The entire product category | Target segments and channels | Competition, capability, share |
The TAM·SAM·SOM breakdown has become the standard framework in venture investing and startup business planning for estimating market opportunity step by step. Its core purpose is to guard against inflated claims about theoretical maximum market size and to push people to also present the share they can realistically secure.
Consider a hypothetical case. Company A builds predictive-maintenance SaaS for manufacturing equipment, with 41 employees and KRW 5.8 billion (≈ US$4,339,400) in revenue last year. While preparing for a Series B, three VCs in a row pushed back on its market-size slide, which said only "Korea manufacturing IT market: KRW 12 trillion (≈ US$8,978,003,900)." The CEO decided to rebuild the market sizing from scratch within eight weeks.
- Manager Kim of the strategy planning team changed the TAM basis from 'the entire manufacturing IT market, KRW 12 trillion (≈ US$8,978,003,900)' to 'annual equipment maintenance spending at manufacturing sites with 50 or more employees' and re-estimated it at KRW 840 billion (≈ US$628,460,300).
- At the SAM stage, the head of sales drew a hard line: "A factory where our engineers can't connect the protocol isn't our market." That narrowed 12,000 target sites to 4,100 in machining and assembly, worth KRW 230 billion (≈ US$172,078,400) a year.
- SOM was validated bottom-up: 4 salespeople × 12 deals per year × average contract value of KRW 48 million (≈ US$35,900) = about KRW 2.3 billion (≈ US$1,720,800). That came within 8% of the top-down 1% market-share assumption, so both figures went into the deck.
- The CFO asked, 'Then what is the basis for next year's KRW 3 billion (≈ US$2,244,500) target?' The team built a separate scenario assuming two more sales hires and two partner channels, and adjusted the target to KRW 2.6 billion (≈ US$1,945,200).
- A second look at SAM density showed auto-parts manufacturers spend 1.7 times more per site than food manufacturers, so the entry order was changed. Six months later, six of the nine new contracts came from auto parts.
- Market-size Q&A time in investor meetings fell from an average of 25 minutes to 7, and Company A closed its Series B round eight weeks later.