Ideas & Opportunity

How do I estimate a market size when the product I'm building doesn't have a category yet?

A starting point

When there's no clean market to point at, build the number from the behavior you're replacing, not from an analyst report that doesn't exist yet. Count how many people or businesses do the painful thing today (a spreadsheet, a manual process, a workaround) and what they already spend to cope with it, then reason about what they'd pay for a real fix. As a starting point, a bottoms-up number you can defend from first principles beats a big top-down number you borrowed from a slide.

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's YC talk is the founder-facing way to reason about a market when you cannot just look up a number. He treats the idea as a hypothesis about fast growth and pushes you to judge the market by the shape of the problem (is it growing, urgent, expensive, frequent, mandatory) rather than a tidy TAM slide. That is the honest starting point for a product whose category does not exist yet: you argue from the problem, not from off-the-shelf data.

How to Evaluate Startup Ideas

On Y Combinator Startup School by Kevin Hale ~50 min

Judge a market by problem quality: growing, urgent, costly, frequent, and mandatory beat a big-sounding but static number.
A market growing on its own is real tailwind, but it is the weakest edge because it is not unique to you.
Frame the whole thing as a hypothesis about why you will grow fast, which forces you to reason instead of citing a report.

Open ycombinator.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 Intermediate

Why we picked it If your product does not fit an existing category, you cannot borrow someone else's market number, so this piece hands you a way to size from the problem instead. Its formula is blunt and useful: how many people have the problem, multiplied by what they already spend to deal with it. That reframes market size around the behavior and budget you are replacing, which is exactly the move you need when no analyst has drawn your box yet.

What is Category Design in Marketing, and Why is it an Important Strategy?

From Play Bigger by Play Bigger ~12 min read

Size a new category as (number of people with the problem) times (what they pay today to solve it), not as a slice of some named market.
The unit that matters is current spend and effort on the workaround you are displacing, so go count that.
Category potential is an argument you make with visible assumptions, so keep every input transparent and easy to challenge.

Open playbigger.com →