The Single Question That Predicts Your Startup's Success
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The Single Question That Predicts Your Startup's Success
Most founders think they know if they have product-market fit.
They're guessing.
I've watched brilliant teams burn millions on products people tolerate but don't love, all while confidently telling investors they're "getting traction."
The problem isn't dishonesty. It's delusion.
We see signals we want to see. A spike in signups. Positive feedback from friends. A big customer who "gets it." These breadcrumbs feel like validation when you're hungry for it.
But product-market fit isn't a feeling. It's not a milestone. It's not even a set of growth metrics.
It's a specific threshold of customer behavior that Sean Ellis discovered after helping 100+ startups grow.
And it can be measured with a single question that cuts through all your team's internal biases and wishful thinking.
I'm going to show you exactly how to measure it, why most founders are afraid to, and how the answers to this one question will fundamentally change how you build your company.
The Question That Changed Everything
In 2009, Sean Ellis was frustrated.
After driving growth at Dropbox, LogMeIn, and Eventbrite, he kept joining startups that claimed to have product-market fit but actually didn't.
So he developed a simple survey to filter out time-wasters:
"How would you feel if you could no longer use [product]?"
With three possible answers:
Very disappointed
Somewhat disappointed
Not disappointed
That's it. Just one question.
But the percentage of users who answered "Very disappointed" predicted startup success with stunning accuracy.
After running this survey with 100+ startups, the pattern became clear:
Companies where over 40% of users would be "Very disappointed" without the product consistently succeeded.
Those under 40% consistently struggled.
This 40% threshold is now known as the "Product-Market Fit Score" - the clearest signal we have that you've built something people genuinely need rather than merely tolerate.
But what makes this single question so powerful?
Why This Question Works When Others Fail
Most product feedback is contaminated by politeness.
When you ask "Do you like our product?" or "Would you recommend our product?" people soften their feedback. They say what they think you want to hear.
Even NPS (Net Promoter Score) suffers from this positivity bias. People will give you a 7 or 8 because they don't want to hurt your feelings.
The genius of the "how would you feel if you could no longer use it" question is that it measures the actual value delivered, not theoretical appreciation.
It asks users to imagine your product vanishing - to mentally simulate life without it. This creates an instant, visceral reaction that reveals their true relationship with your product.
The "very disappointed" answer isn't just positive feedback. It's evidence of dependency. Of habitual usage. Of genuine value being delivered.
You can't trick, charm, or bribe your way to a high score on this question.
Either your product has become essential to some portion of your users, or it hasn't.
And that distinction is everything.
The Startling Truth Most Founders Avoid
Here's why most founders never run this survey:
They don't want to know the answer.
Take Superhuman, the email client built for speed and focus.
Founder Rahul Vohra publicly credited Sean Ellis's question for helping them tune product-market fit. They ran the survey—and only 22% of users said they'd be very disappointed without Superhuman.
Rahul didn't panic. He segmented users and found that a small group of busy professionals and founders had much higher scores.
Instead of chasing more users, they narrowed their focus. They doubled down on their high-PMF segment.
They rebuilt onboarding, retooled features, and even adjusted marketing language based on survey answers.
Eventually, they crossed the 40% line.
Their growth took off—funding from a16z, viral waitlists, and a product people evangelized. Not because they chased growth. But because they validated their product's core addiction loop.
The pain of honest feedback is temporary. The pain of building something nobody truly needs is permanent.
This survey isn't just measurement. It's a forcing function for difficult but necessary decisions.
The Full Product-Market Fit Survey That Changed the Game
While the core question gives you your PMF score, Sean Ellis didn't stop there.
The complete survey includes follow-up questions that turn your score into actionable insight:
1. The Core Question: "How would you feel if you could no longer use [product]?"
Very disappointed
Somewhat disappointed
Not disappointed
2. The "Why" Question: "What would you miss most about [product]?" (Open-ended)
3. The Primary Benefit Question: "What is the primary benefit you receive from [product]?" (Open-ended)
4. The User Type Question: "What type of people do you think would most benefit from [product]?" (Open-ended)
5. The Alternative Question: "How would you improve [product]?" (Open-ended)
Each question serves a specific purpose:
The "Why" question reveals which features create actual dependency versus which ones merely sound good.
The "Primary Benefit" question often exposes disconnect between your marketing language and actual user value.
The "User Type" question uncovers how existing users view your ideal customer, which is often different from your target personas.
The "Alternative" question separates must-have improvements from nice-to-haves.
Together, these five questions don't just tell you if you have product-market fit. They tell you exactly what to do next, regardless of your score.
How to Run Your PMF Survey (Without Bias)
The mechanics of running this survey matter enormously:
1. Survey a Minimum of 40 Users
Smaller sample sizes produce wildly unreliable results.
2. Only Survey Users With Adequate Experience
They should have enough usage to give an informed opinion - typically users who have:
Used your product at least twice
Used your product in the last two weeks
Experienced your core product value (completed key actions)
3. Avoid Sampling Bias
Don't just survey your power users or most engaged customers. You need a representative sample across your user base.
4. Keep the Survey Anonymous
Users provide more honest feedback when responses aren't tied to their identity.
5. Don't "Prime the Pump"
The email invitation should be neutral. Don't say "we value your feedback" or "help us improve" as this biases toward positive responses.
6. Segment Your Results
Analyze your data by:
User age/cohort
Usage frequency
Customer segment
Acquisition source
Often, product-market fit exists in specific segments even when your overall score is below 40%.
7. Run This Survey Consistently
Product-market fit isn't permanent. Track your score quarterly to watch for erosion or improvement.
When You Don't Have Product-Market Fit (Yet)
Most startups don't hit the 40% threshold on their first survey. When you're below the line, there are three valid strategies:
Strategy #1: Narrow Your Focus
If a specific segment shows higher disappointment rates, double down on them. Stop trying to please everyone and obsessively target your most promising users.
Strategy #2: Find the Bright Spots
Identify which specific features or use cases users mention most in the "why" section of the survey. Even with a low overall PMF score, these bright spots show what's working.
Strategy #3: Kill It
Sometimes the right move is shutting down and starting over.
If your score is below 25%, with no promising segments or features, and you've already made significant product iterations, continuing is often the most expensive way to fail.
I respect founders who can look at clear data and make the hard call to end one venture to free up resources for the next.
This isn't failure. It's efficient learning.
When You Have Achieved Product-Market Fit
Crossing the 40% threshold doesn't mean you're done. It means you've earned the right to scale.
Your next steps:
1. Double Down on Acquisition
With validated product-market fit, customer acquisition becomes an investment rather than an expense. Money in should reliably produce more money out.
2. Expand Only to Adjacent Fits
The temptation with PMF is to broaden your product. Resist this. Instead, find adjacent use cases or segments where your core value proposition remains relevant.
3. Build a Roadmap Based on "Very Disappointed" Feedback
The improvements requested by your most dedicated users should form your near-term roadmap. They're already convinced of your core value; their suggestions will enhance retention and word-of-mouth.
4. Optimize Onboarding for "Aha" Moments
Review the "primary benefit" responses from your survey. These reveal your product's key "aha moments." Redesign your onboarding to deliver these moments as quickly as possible.
5. Craft Messaging Around User Language
The exact words your "very disappointed" users use to describe your benefit should become your marketing language. Don't improve on their phrasing - mimic it exactly.
The Question Behind the Question
The brilliance of the Sean Ellis test isn't just that it measures product-market fit objectively.
It's that it forces you to confront the most important question in business:
Have you built something people truly need, or merely something they're willing to try?
Thousands of startups are building products people will sign up for but won't miss if they disappeared. That's not success. It's expensive entertainment.
Your mission isn't to build something people like.
It's to build something they can't imagine living without.
The 40% threshold isn't arbitrary. It's the dividing line between products that merely exist and products that matter.
Which side are you on?
Run the survey. Face the truth. Then build accordingly.
Your move.
Thank you for reading.
– Scott