📖 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 →
📄 Article
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Free
Beginner
Why we picked it
The idea that started the lean movement, from the person who coined it. No business plan survives first contact with customers, so stop defending assumptions at your desk and go test them on real people. Short, blunt, and foundational.
From
steveblank.com
by Steve Blank
~8 min read
- Your idea is a set of guesses until customers test it.
- Facts live outside the building, not in your plan.
- Expect to be wrong, and plan to learn from it.
Open
steveblank.com →
📄 Article
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Free
Intermediate
Why we picked it
This is the cleanest walkthrough of building a market number from the ground up: count the real end users who fit your profile, multiply by revenue per user, then sanity check with a top down view. It matches our short answer exactly, start from a real count instead of a national figure divided by a guess. Use it as the template for the number you eventually show an investor.
From
Disciplined Entrepreneurship (Bill Aulet, MIT)
by Bill Aulet
- TAM equals real end users times annual revenue per user.
- Build bottom up first, then cross check top down.
- Win a beachhead you can actually reach, not the whole country.
Open
d-eship.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
Beginner
Why we picked it
A clean definition of the three market layers with the key distinction spelled out: TAM is the whole opportunity, SAM is what you can realistically serve, and SOM is what you will actually win. If the vocabulary still confuses you, this untangles it fast and shows why the SOM, your real near term slice, is the number that matters most.
From
Forum Ventures
by Forum Ventures
- TAM is the whole market, SAM what you can serve, SOM what you win
- SOM, your realistic near term slice, is what investors stress test
- Present both top down and bottom up to be credible
Open
forumvc.com →
📄 Article
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Free
Intermediate
Why we picked it
A side-by-side of both methods that makes clear why you use bottom-up as your primary number and top-down only as a rough check. That distinction is exactly what protects you when the top-down Indian data is thin. Read it to decide which method to lead with in your deck.
From
Waveup
by Waveup
14 min read
- Bottom-up is defensible, top-down is only a directional check
- Use both and reconcile them against each other
- Lead with the method your data can actually support
Open
waveup.com →
✍️ Essay
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India
Free
Intermediate
Why we picked it
Essential reading for anyone sizing an Indian market. Pai shows that India's billion people are not one payable market: roughly a hundred million strong India1 is the real paying base for most startups, not the headline population. It is the sharpest correction to the huge TAM trap in an Indian context, and helps you size the segment that will actually transact.
From
Sajith Pai
by Sajith Pai
- India1, around a hundred million people, is the real paying market for most startups
- A billion population is not a billion paying customers
- Size the segment that can actually transact, not the whole country
Open
sajithpai.com →
✍️ Essay
✓ Link checked
India
Free
Intermediate
Why we picked it
Before you optimize a byte, you need to know who you are building for, and Pai's India1, India2, India3 framing is the clearest map of the Indian market you will find. He explains the English tax and why the vernacular, low trust, price sensitive India2 user behaves so differently from the metro user founders usually resemble. This is the market context that makes the technical advice matter.
From
SajithPai.com
by Sajith Pai
Long read
- India is several distinct markets, and India2 is not a smaller India1
- Language and trust barriers can matter more than raw speed
- Design in the user's own language rather than translating English later
Open
sajithpai.com →
📄 Article
✓ Link checked
India
Free
Intermediate
Why we picked it
Blume's annual report is the single best data-grounded read on what is actually happening in Indian internet and consumption, not what is trending on VC Twitter in San Francisco. It shows you adoption curves (UPI, quick commerce, ONDC, how few households actually shop online) so you can pressure-test whether a hyped trend has the demand base to land here. Treat it as a starting map of Indian reality, then judge your specific trend against it.
From
Blume Ventures
by Sajith Pai, Anurag Pagaria and team (Blume Ventures)
~180 charts
- Grounds trend-spotting in real Indian adoption data (income distribution, online-shopping penetration, UPI-native monetization) instead of imported hype.
- Indian startups are building a distinct playbook (micro-subscriptions on UPI Autopay, DPI rails) that has no clean US analogue, so copying a US trend directly often misses the real opportunity.
- A trend can be huge in raw numbers yet thin in monetizable demand: the report repeatedly separates users from paying users.
Open
blume.vc →
📄 Article
✓ Link checked
Free
Beginner
Why we picked it
The cleanest distillation of the one framework that turns a customer chat into a relationship instead of a survey. The three rules (talk about their life not your idea, ask about the past not hypotheticals, and chase real commitments of time, reputation, or money) are exactly how you get an early customer to tell you what nearly stopped them from buying and who else you should talk to. Rekhi is a product leader, so the examples are operator-grade, not book-report fluff.
From
Sachin Rekhi's Blog
by Sachin Rekhi
10 min read
- Never pitch your idea in the conversation; ask how they handle the problem today and what it costs them, so praise can't lie to you.
- The strongest signal is a commitment that costs them something: a trial, an intro to a colleague, or a pre-order.
- 'Would you buy this?' teaches you nothing; 'walk me through the last time you dealt with this' surfaces the real story and the referral.
Open
sachinrekhi.com →
Why we picked it
The permission slip to recruit users by hand, do things manually, and deliver 'insanely great' experiences to your first few customers. The cheapest, most honest way to validate demand is to go get it one person at a time.
From
paulgraham.com
by Paul Graham
~15 min read
- Recruit your first users manually, don't wait for them to come.
- A tiny group of users who love you beats a big group who like you.
- Manual, unscalable effort early is a feature, not a failure.
Open
paulgraham.com →
