What's the difference between defining a niche and just being too small to matter?
The short answer
A good niche is small in headcount but deep in pain and willingness to pay, while a bad niche is small because there simply isn't enough there to build on. Test it by math: number of reachable customers times what they'd realistically pay times how often they buy. If a tight niche of a few thousand desperate customers can fund a real business, that's focus, not smallness. If even winning 100 percent of the niche wouldn't sustain you, you're not niching, you're cornering yourself, so treat this as a sizing check rather than a gut feeling.
Go deeper, your way
3 hand-picked resources, 3 link-checked. Pick how you want to dig in.
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Why we picked it
Founders often keep validating because they secretly doubt the idea itself, so a structured way to judge the idea is half the readiness question. YC partner Jared Friedman gives an idea quality score across four criteria (how big, founder/market fit, how sure you are the problem is real, and whether you have a genuine insight) plus the bad filters that make founders quietly reject their best ideas. It is the honest bar to check your idea against before you commit to building. A starting framework, not a scorecard to obsess over.
Rate an idea on four criteria and average them, rather than trusting a gut yes or no.
Great companies usually started from a good enough idea plus strong execution, not a brilliant one, so waiting for the perfect idea is itself a mistake.
Watch for filters (seems hard, boring space, too ambitious, competitors exist) that make you reject strong ideas without realising it.
Why we picked it
This is the canonical argument that you do not need a mass market to build something real, you need a small number of people who deeply want what you make. It is the cleanest way to see that a niche is not the same as being too small, because 1,000 people who buy everything you make is a business, while 100,000 people who half-care is not. Read it as a starting point for reframing what 'big enough' actually means.
Why we picked it
This is written by Visible, a platform that sits on the investor side of the table, so it explains bottom-up sizing the way a VC actually reads it. It is direct about why the top-down number collapses under scrutiny and why the bottom-up build wins credibility, which is exactly the tension you are describing. Use it to decide what to lead with, then show top-down only as a sanity check.
Bottom-up sizing (count real customers, multiply by realistic revenue per customer) is more defensible because every assumption is one an investor can poke at and you can answer.
A top-down number pulled from an industry report signals you Googled a big figure rather than understanding who buys, how many exist, and what they pay.
The strongest move is to lead with your bottoms-up number and use top-down as triangulation: if the two diverge a lot, revisit your assumptions before the meeting.
