TAM, SAM, and SOM

Warm-up: How big is your market?

2 warm-up questions

• If someone asked you 'how big is the market for online language tutoring?', how would you even begin to estimate it?
• First try: an investor leans forward and asks 'so — how big is your market?'. Answer for any startup idea you like. 30 seconds.

Reading: TAM, SAM, and SOM

Read a 359-word text about TAM, SAM, and SOM

TAM, SAM, and SOM When pitching to investors or planning your growth strategy, you need to articulate the size of your market opportunity. TAM, SAM, and SOM are three nested metrics that help you communicate how big your opportunity is, how much you can realistically address, and what you're actually targeting in the near term. Total Addressable Market (TAM) TAM represents the total revenue opportunity if you achieved 100% market share in your category. It's the entire universe of potential customers who could benefit from your solution. For a project management tool, TAM might include every business in the world that needs to manage projects—hundreds of billions in potential revenue. TAM is always the largest number and represents the theoretical maximum. Serviceable Addressable Market (SAM) SAM is the portion of TAM that your product can actually serve. It accounts for geographic limitations, product capabilities, and go-to-market constraints. If you only operate in North America and only serve B2B companies, your SAM is much smaller than your TAM. SAM is still optimistic, but it's grounded in the reality of what your business model can reach. Serviceable Obtainable Market (SOM) SOM is what you can realistically capture in the next 1-3 years given your resources, competition, and growth rate. If your SAM is $10 billion, your SOM might be $50 million—the slice you think you can actually win. SOM should be ambitious but achievable, backed by your go-to-market strategy, sales capacity, and growth trajectory. Calculating Market Size There are two main approaches: top-down and bottom-up. Top-down starts with industry research reports ("The project management software market is $5B"). Bottom-up builds from your customer profile ("There are 500,000 companies in our target segment, each spending $10,000/year"). Investors prefer bottom-up because it shows you understand your customer and unit economics. Why Investors Care Venture capitalists need TAM to be large enough to justify their investment. They're looking for markets of at least $1 billion (often $10 billion+) because they need portfolio companies that can grow to $100M+ in revenue. If your TAM is only $100M, there's not enough room for a venture-scale outcome. Understanding and articulating your market size is essential for fundraising.

Vocabulary: Market Size Vocabulary

8 items

Framework: The Market Sizing Framework

The Market Sizing Framework, 5 steps

The Market Sizing Framework: A structured approach to calculating and presenting market size to investors. Start with the total opportunity and narrow down to what you can realistically capture. Investors use this to assess whether the opportunity is large enough.

Reading: A model market-sizing walkthrough

Read a 340-word text about A model market-sizing walkthrough

A model market-sizing walkthrough One complete answer to 'how big is your market?', performed for a startup selling scheduling software to dental clinics. Every number connects to the next — that's what makes it credible. The moves in bold: TAM, SAM, SOM bottom-up, growth driver, capture strategy. The walkthrough "Let me size it from the top down to what we'll actually win. The total addressable market: practice-management software for healthcare clinics is roughly $12 billion globally, per the latest IDC estimate, growing about 11% a year as clinics digitise. Our serviceable addressable market is the slice our product can genuinely serve today: dental clinics in Europe. Bottom-up, that's about 180,000 clinics; the mid-size ones we target — three or more chairs — number around 90,000, and they spend on average €4,000 a year on scheduling and patient-communication tools. That's a €360 million SAM — counted, not quoted from a report. Our serviceable obtainable market — what we can realistically capture in three years — is about €18 million, or 5% of SAM. And we can decompose that: €18 million at our €3,600 average contract value is 5,000 clinics. Our current sales motion closes about 40 clinics a month and is improving — so 5,000 in three years is ambitious but arithmetic, not poetry. Why the timing works: two of the three legacy vendors in this space still sell on-premise software, and clinics replace systems on a seven-to-ten-year cycle that's peaking now. And how we capture it: clinics talk to each other regionally — our first 200 customers came from three cities, referral-led. We expand city by city, which keeps CAC low and density high. So: $12 billion TAM, €360 million SAM, €18 million three-year SOM — and a sales motion that's already producing its share of it." Why investors trust this Each layer shrinks for a stated reason (geography, segment, sales capacity). The SOM is bottom-up twice over — customers × price, then deals-per-month × time. An investor can check every multiplication — and being checkable is the whole game.

Practice: Practice: Market Size Concepts

Gap-fill exercise, 6 items

• ____ represents the total revenue opportunity if you captured the entire market.
• ____ is the portion of the market you can actually serve given your product and go-to-market strategy.
• ____ is what you can realistically capture in the next 1-3 years.
• The ____ approach calculates market size by counting target customers and multiplying by price.
• Investors look for ____ outcomes where startups can reach $100M+ in revenue.
• Our current ____ is 2%, meaning we serve 2% of our target market.

Practice: Classify the market-sizing statement

Matching exercise, 6 items

• The global market for our category is $12B, per IDC
• European dental clinics our product can serve: €360M
• 5% of SAM in three years: €18M
• 90,000 clinics × €4,000 average spend
• 'Analysts value the space at $5B'
• Referral-led, city-by-city expansion

Dialogue: Role Play: Presenting Market Sizing to Investors

Role-play: You're presenting your market sizing analysis during a pitch meeting with investors who want to understand the scale of your opportunity. (4 lines)

• investor: Let's talk about market size. Walk me through your TAM, SAM, and SOM analysis. How big is this opportunity really?
• investor: Those are interesting numbers, but I've seen a lot of founders inflate their TAM. How did you build these estimates? Are they top-down or bottom-up?
• investor: I like the bottom-up approach. But $160 million SOM in three to five years is ambitious for a company at your stage. What's your path to capturing that share?
• investor: What about competition? If this market is $12 billion, there must be incumbents. How do you size the market with competitors already in it?

Discussion: Your mission: size your market

3 discussion questions

• Mission: answer 'how big is your market?' for YOUR startup (real or invented) in 90 seconds: a top-down TAM with a source style ('per industry reports'), a SAM filtered by stated criteria, and a bottom-up SOM — customers × price, cross-checked against your sales capacity. Success = three nested numbers that shrink for stated reasons, at least two multiplications an investor could check, and a one-line capture strategy. (Tutor: play the investor and recompute one multiplication out loud — make sure it survives.)
• Second take: the investor pushes — 'your TAM is too small for venture scale.' Respond honestly: either defend the expansion path that grows the TAM, or make the case for why the business is great at this size.
• Compare with your first-try answer. How many layers did your first answer have — and which multiplication was missing?