TAM, SAM, SOM: these funny acronyms are critical to any founder, but especially to a Vibe Founder. While most businesses aren't "venture scale", every one of them has to make decisions that support their survival and longevity. Before we worry about WHAT, we must think about WHO we're serving, the problems they have, and the value they attribute to solutions.

Vibe Founders have many different goals:

• Making enough to support yourself and your passions

• Building a small team and business to support your lifestyle

• Shooting for the moon to create a unicorn business

However, our goals don't change our need to understand the fundamentals of our business. Fortunately, there are well-established methods for thinking about your market, aka who you're selling to. Here's a quick primer.

Let’s start with the basics — because way too many founders still wing this.

• TAM is Total Addressable Market: the big, top-line number. If every possible customer bought your product, how much money could you make?

• SAM is Serviceable Available Market: a slice of the TAM that your current business model, features, or geography can actually serve.

• SOM is Serviceable Obtainable Market: your real near-term opportunity — based on go-to-market strategy, resources, and traction.

TAM is about vision. SOM is about execution. You need both. But you especially need TAM if you ever want to raise money, enter new markets, or just to sanity-check your roadmap.

There are two main ways to calculate TAM, and both have their pros and cons.

This is the classic “analyst report” approach. Start with the entire industry’s spend — then narrow it.

• Step 1: Find a big, reputable number — industry size, annual spend, etc.
  Example: “$200B spent annually on health & wellness.”

• Step 2: Apply filters — geography, demographics, behavior.
  Example: “We’re targeting U.S. men aged 25–45 who use supplements = $10B.”

• Step 3: Apply assumptions — e.g., what % will switch, what % we can reach.
  Example: “Assume 10% adoption → $1B TAM.”

This is great for fundraising. It shows scale, narrative, and optionality if you need to pivot. But it’s easy to BS — and investors know it.

This is the builder’s approach. Start with what you sell and who you’re selling to.

• Step 1: Identify your ideal customer and their spend.
  Example: “Our product costs $50/mo. Our early users are freelance designers.”

• Step 2: Estimate how many of those customers exist.
  Example: “There are ~5M freelance designers globally.”

• Step 3: Multiply: $50/mo × 12 × 5M = $3B TAM

This method forces clarity: you need to define your customer, your pricing, and your assumptions. It’s grounded. It’s honest. It’s usually smaller — but that’s a good thing. It helps you make better decisions faster.

Now that we have the fundamentals in place, let’s walk through a couple of examples.

• Start with: $150B global fitness market

• Focus on: smartphone users aged 20–40

• Narrow to: digital fitness subscriptions ($15B)

• Target: English-speaking markets = $5B

• Assume: 5% market penetration = $250M TAM

• Product: $30/month tool for solo consultants

• Target audience: ~10M globally

• Estimate TAM: 10M × $30 × 12 = $3.6B

• SAM (realistically reachable users): maybe 1M = $360M

• SOM (first 12 months): 10K users = $3.6M

scssCopyEdit"Help me estimate the top-down TAM for [industry]. Start with global market size, then narrow by geography, demographics, and known spend."

cssCopyEdit"Based on [my product], who is my most likely initial customer segment? Estimate size, CAC, and potential ARPU to calculate bottoms-up TAM."

arduinoCopyEdit"Compare top-down and bottoms-up TAM for my startup idea: [insert idea]. Highlight risks and blind spots in each."

cssCopyEdit"Create a TAM slide for a pitch deck using both top-down and bottoms-up methods. Assume I’m targeting [X niche in Y market]."

• TAM = Total Addressable Market (big picture),
  SAM = Serviceable Available Market (reachable now),
  SOM = Serviceable Obtainable Market (realistic near-term win).

• Top-down TAM starts with industry size and narrows from there. Great for pitching. Easy to fudge.

• Bottoms-up TAM starts with your product, pricing, and customer count. Great for planning. Harder to fake.

• Use both: top-down for vision, bottoms-up for reality.

• Top-down is best if you're fundraising, bottroms-up is always useful

• Let AI help — it can size markets, suggest segments, and pressure-test your assumptions in minutes. Just prompt it smartly.