Customers & Research

What are the most common mistakes founders make when sizing their market, and how do I avoid faking a big TAM?

A starting point

The classic mistake is starting from a giant global number and multiplying down with invented percentages (the 1% of a billion-dollar market trap), which no serious investor believes and which fools you more than them. Build it bottom-up: realistic number of buyers times a price they'll actually pay, then sanity-check against comparable companies' revenue. A smaller, defensible number you can explain beats a huge one you can't, and it forces you to know who your customer really is.

Go deeper

Hand-picked from around the web, each with a note on why it earns your time.

3 resources 3 link-checked Watch Read

Watch

▶️ Video
✓ Link checked Free Beginner

Why we picked it Kevin Hale (YC partner, Wufoo co-founder) walks through how to package your idea so an investor believes it can grow fast, and a big part of that is telling the founder story so 'why you' lands instead of sounding like a boast. It is practical and script-level: how to open, what to lead with, and how to make your unfair edge legible in the first minute. Watch it once before you write a single pitch line.

How to Pitch Your Startup

On Y Combinator by Kevin Hale ~35 min

How to Pitch Your Startup
  • A pitch is really a hypothesis about why this company can grow quickly, so your 'why you' has to feed directly into that growth story, not sit as a separate bio slide.
  • Investors weigh how well you can sell and tell the story, so evidence you understand your customer beats abstract claims about your background.
  • Lead with clarity: make the problem, your insight, and why you are the one to solve it understandable in a sentence or two.
Watch on YouTube youtube.com →

Read

✍️ Essay
✓ Link checked Free Intermediate

Why we picked it When there is no category report to point at, you have to build the number yourself, and this is the essay that teaches you how. It walks through bottoms-up sizing (start from your actual customer, their willingness to pay, and how you will reach them) and shows why the top-down 'we just need 1 percent of a huge market' story falls apart. Treat it as the method for a defensible estimate, not a promise about how big you will get.

16 More Startup Metrics

From Andreessen Horowitz by Anu Hariharan, Frank Chen, Jeff Jordan ~20 min read

  • Build TAM from the bottom up: real customer profile times realistic price times how many you can actually reach and sell to.
  • Top-down percentages inflate the number and hide the hard part, which is distribution and go to market.
  • Some of the best companies (eBay, Airbnb) started against a market that looked small, then expanded the use case, so a modest starting number is not a dealbreaker.
Open a16z.com →
📄 Article
✓ Link checked Free Beginner

Why we picked it This piece names the exact trap you are trying to avoid: googling an industry stat and assuming you just need 1 percent of it to build a billion-dollar company. It calls that the wrong approach and walks you to the fix, sizing TAM as annual revenue per customer times the number of customers who actually match your profile and would pay. It is short, practical, and aimed at the pitch slide where founders most often fake a big TAM.

5 critical pitch deck slides most founders get wrong

From TechCrunch by Jose Cayasso Short read, roughly 8 to 10 minutes

  • The 1 percent of a huge market claim reads as fantasy math to investors and quietly costs you credibility on the market slide.
  • Size the market from the bottom up: revenue per customer times the count of customers who genuinely fit your target and are willing to pay.
  • Doing this forces you to actually know your target persona and buyer, which is the real thing investors are checking for.
Open techcrunch.com →

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