✍️ Essay
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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.
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
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Free
Beginner
Why we picked it
The definitive short read on why disruptive ideas get dismissed as toys, and why that dismissal is your opening. It reframes what looks trivial today as the thing that owns the market tomorrow, essential for spotting trends before they're obvious.
From
cdixon.org
by Chris Dixon
~5 min read
- Disruptive products launch under-powered and get laughed off by incumbents.
- Because experts ignore 'toys,' the early builder gets a head start no one contests.
- Judge a fast-growing product by what it becomes in five years, not what it does today.
Open
cdixon.org →
✍️ Essay
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Free
Beginner
Why we picked it
The definitive essay on where good ideas come from: notice problems you personally have, don't force it. Use it as the lens for judging whether your idea is a real problem or a solution in search of one.
From
paulgraham.com
by Paul Graham
~20 min read
- Live in the future and build what's missing.
- The best ideas look like bad ideas at first (schleps and hard-to-explain).
- Start with problems you have, in a domain you actually know.
Open
paulgraham.com →
📖 Book
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Paid
Beginner
Why we picked it
The single best thing ever written on customer conversations. It teaches you to ask about the customer's life and past behaviour, not your idea, so you can't be lied to. If a founder reads one thing before talking to a single customer, it's this.
From
momtestbook.com
by Rob Fitzpatrick
~130 pages
- Talk about their life, not your idea.
- Ask about specifics in the past, not opinions about the future.
- 'That's so cool, I'd totally buy it' is a compliment, not data, dig for commitment and evidence.
Open
momtestbook.com →
✍️ Essay
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Free
Advanced
Why we picked it
Before you sweat which side to seed, Gurley helps you judge whether your marketplace is even structurally worth building. He lays out ten factors (fragmentation, frequency, payment flow, network effects) that separate marketplaces that snowball from ones that stay empty. It is the investor lens on why some two sided ideas never reach liquidity no matter how hard you push.
From
Above the Crowd
by Bill Gurley
20 min read
- Great marketplaces enhance a market, they do not just aggregate it
- High fragmentation on both sides makes a marketplace more defensible
- Being in the payment flow is far stronger than sitting outside it
Open
abovethecrowd.com →
✍️ Essay
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India
Free
Intermediate
Why we picked it
Sajith Pai is an India VC, and he tells on himself here: he passed on WhiteHat Jr. by trusting a headline India TAM number, then learned it was the wrong way to think. The piece grounds you in real reachable demand (the actual India1 consuming class and a beachhead you can serve) rather than a paper market pulled from a slide. Read it as a starting point for why a smaller, real market usually beats a big, imaginary one.
From
sajithpai.com
by Sajith Pai
- Headline India TAM figures are a blunt tool that measure existing demand, not the market you can actually reach or expand into.
- Size the problem and a concrete beachhead you can win first, since a targetable immediate market funds the next round even when TAM looks small.
- Most Indian startups are really addressing India1, the consuming class, so honest sizing starts from who will actually pay, not the full population.
Open
sajithpai.com →
✍️ Essay
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Free
Intermediate
Why we picked it
Most market sizing advice online is generic TAM SAM SOM filler. This one is written by an investor, backed by a survey of 30 VCs, and it is honest about the thing that matters: a big number pulled from an industry report proves nothing. It walks you through building the number bottom up (customers times what they pay you per year), which forces you to confront whether real people will actually pay, and that is the honest test of whether an idea can grow past a niche.
From
Pear VC
by Ian Taylor
~15 min read
- Size the market bottom up (count of real customers times annual revenue per customer), not by claiming a percent of some giant top down figure.
- TAM, SAM, and SOM are used loosely across the industry, so state your assumptions plainly instead of hiding behind the acronyms.
- Project the market out five or more years and include how you would actually reach and acquire customers, since a market you cannot serve is not your market.
Open
pear.vc →
📄 Article
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Free
Intermediate
Why we picked it
A founder-facing guide that ties market sizing to the question investors are really asking, and warns against describing only your first segment without the expansion logic. It helps you frame a small starting market as the front of a larger story. Concrete on what to actually show and how far out to project.
From
22nd Century Frontier
by Petar Dimov
~12 min read
- Investors want the expansion path, not just your first customer segment.
- Explain the conditions that will make the market grow over time.
- Size for a few years out, grounded in assumptions you can defend.
Open
22ndcenturyfrontier.com →
📖 Book
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Paid
Advanced
Why we picked it
If you truly have no category, this is the book on deliberately designing one, which reframes sizing as creating demand rather than measuring it. It studies companies that made customers change what they expect and buy. Useful for the strategic story around your number, less so for the arithmetic itself.
From
playbigger.com
by Al Ramadan, Dave Peterson, Christopher Lochhead, Kevin Maney
Book
- A new category is something you design, not something you find in a report.
- Category kings create demand where none existed before.
- Frame your market as the problem you are teaching people to name.
Open
playbigger.com →
✍️ Essay
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Free
Intermediate
Why we picked it
The essay that put 'product-market fit' into the startup vocabulary. Read it for the gut-level description of what PMF feels like when it's happening vs when it isn't, the intuition behind the metrics.
From
pmarchive.com
by Marc Andreessen
~15 min read
- Market matters most; a great market pulls product out of a startup.
- You can feel PMF, customers buy as fast as you can ship.
- Before PMF, do whatever it takes to get there; nothing else counts.
Open
pmarchive.com →
Why we picked it
Moore's beachhead idea is the definitive case for winning one narrow segment before you touch the broader market, which is precisely how you compete when big players already own the mainstream. He argues you pick a target segment big enough to matter but small enough to lead, then dominate it before expanding. In a crowded market that focus is not timidity, it is the only way a small team gets a foothold.
From
Geoffrey A. Moore
by Geoffrey A. Moore
~240 pages
- Win a single beachhead segment completely before spreading resources across a broad market
- Choose a niche big enough to matter but small enough to lead, and concentrate everything there
- Mainstream, pragmatic buyers need a compelling, proven reason to switch, which a narrow focus lets you deliver credibly
Open
geoffreyamoore.com →
📄 Article
Free
Intermediate
Why we picked it
Blank separates a new market, where customers do something they could not before, from existing and resegmented markets, and shows why the sizing rules differ for each. Naming your market type tells you whether an analyst report even applies to you. Directly useful when your product created the category and there is nothing to point at.
From
Inc.
by Steve Blank
~8 min read
- In a new market there are no competitors and no existing report to cite.
- Size a new market from the behavior it enables, not from a category total.
- Know your market type before you choose a sizing method.
Open
inc.com →
