When Someone Asks About Market Size, Answer With Three Numbers

Tell an investor "the market is worth ₩100 trillion" — roughly $75 billion — and the follow-up question is always the same: "So how much of that can you actually capture?"

The fact that a ₩100 trillion market exists and the fact that your business can actually make money in it are two entirely different things. TAM, SAM, and SOM is the framework that makes that difference visible, piece by piece.

It's a concept every founder, product manager, and business planner needs to know — and one people mix up surprisingly often. Here's the simple version.

A Fishing Analogy Makes It Click

Think about how many fish there are in the sea.

TAM is every fish in the ocean. How many tuna are swimming in the Pacific. It's the total market that theoretically exists — the full size of demand out there, whether or not you can catch any of it.

SAM is the fish in the waters your boat can reach. You don't count the whole Pacific — only the fish within your boat's range, and only the kinds your nets can catch. It's the slice of the market your product can actually reach.

SOM is the fish you'll actually haul in today. Given the size of your boat, the number of crew, your fuel, and the competing boats around you, it's what you can realistically bring home. It's the revenue you can capture with the capabilities you have right now.

Keeping the Three Straight

TAM (Total Addressable Market) — the total market

TAM is the total market size assuming every potential customer who has the problem your product solves actually buys your product. No constraints of geography, competition, or capability — it's the theoretical maximum.

If you're building an online English-learning service, TAM is everyone in the world who wants to learn English. That could be billions of people. It isn't realistic, but it shows you where the ceiling of the market sits.

TAM matters because if this number is too small, even flawless execution won't add up to a meaningful business. Investors look at TAM to answer one question: is this market big enough to be worth investing in?

SAM (Serviceable Addressable Market) — the market you can serve

SAM is the portion of TAM your product can actually reach — the market that remains after filtering by geography, language, price point, distribution channels, and the nature of your product.

Take that same online English-learning service: if it runs in Korean and supports only Korean payment systems, SAM narrows to "adults in Korea who want to learn English online." A fraction of TAM.

SAM is the realistic arena for your business. It shows how big the market you can actually compete in is.

SOM (Serviceable Obtainable Market) — the market you can win

SOM is the share of SAM you can actually capture in the near term — usually one to three years. It's a number that realistically reflects your current marketing budget, sales headcount, brand awareness, and competitive landscape.

Even if Korea's online English-education market (your SAM) is worth ₩500 billion (about $370 million), capturing a 2% share in year one puts your SOM at ₩10 billion (about $7.4 million). That becomes the actual revenue target in your business plan.

SOM is the most grounded of the three numbers, and it's the one investors scrutinize hardest. You need a convincing answer to "why do you believe you can take 2%?"

Thinking It Through With a Real Example

Say you're launching a subscription service for pet health food.

TAM. The global pet food market — roughly ₩150 trillion, or about $110 billion. Kibble, treats, health food, supplements, all of it. You will never swallow this market whole, but the market itself is plenty big.

SAM. Korea's premium dog health-food market. From all pet food, keep only the health-food category; within that, only dogs; within that, only the premium price tier. Call it roughly ₩300 billion (about $220 million).

SOM. The customers you can win in year one: the Seoul–Gyeonggi metro area, small-dog owners, on a monthly subscription model. Factoring in your marketing budget and logistics capacity, that's 5,000 monthly subscribers and about ₩3 billion (about $2.2 million) in annual revenue. That's a realistic first-year target.

Same business, but the numbers narrow from ₩150 trillion to ₩300 billion to ₩3 billion. Showing all three together is how you convey the size of the market (the opportunity) and the realism of your execution (the plan) at the same time.

Three Common Mistakes

First: inflating TAM and stopping there. "The AI market is worth ₩1,000 trillion" (about $740 billion) sounds impressive, but it means nothing if you can't answer what your product's SAM and SOM are. Investors care less about the size of your TAM than about the logic that narrows it down to your SOM.

Second: confusing SAM with SOM. "The Korean market is ₩500 billion, so our revenue target is ₩500 billion" doesn't hold up. SAM is the entire serviceable market, competitors included; SOM is the slice of it you can actually take. No business plan assumes 100% market share.

Third: setting SOM too conservatively. Swing the other way and shrink SOM too far, and you can no longer make the case for why anyone should invest. SOM should be realistic but ambitious. What matters isn't the size of the number — it's presenting a concrete path to reaching it: the channels, the strategy, the resources.

There Are Two Ways to Run the Numbers

Top-Down

Start from big market data and narrow down. Pull the total market size (TAM) from industry reports, filter by region, category, and price point to get SAM, then multiply by your projected market share to arrive at SOM.

The upside: it's fast and great for showing the big picture. The downside: the numbers are abstract, which leaves you exposed to the question "so what is that actually based on?"

Bottom-Up

Start from the smallest unit and build upward. Annual spend per customer × the number of customers you can win = SOM. Then work backward from SOM's share of the overall market to estimate SAM and TAM.

The upside: every number has concrete footing. The downside: you can lose sight of the market's big picture.

In practice, you do both. Top-down shows how big the market is; bottom-up proves your execution plan is real. And if the two approaches produce wildly different numbers, an assumption is wrong somewhere.

How It Goes Into Your Business Plan

When presenting to investors, this sequence flows naturally.

Start with TAM to show the size of the opportunity: "This market is plenty big." Then narrow the focus with SAM: "Within it, this is the arena where we compete." Finish with SOM as the execution plan: "Here is how much we'll capture in year one, and here's how."

Then show the path that expands from SOM to SAM, and from SAM to TAM: "We start in Seoul and go national; we start in Korea and go to Asia." That expansion path becomes the growth story of the business.

If you want it in one sentence: TAM is the size of the dream, SAM is the arena you can fight in, and SOM is tomorrow's revenue. Show all three together, and you convey a business's potential and its realism at once.