"Would you be very disappointed if you could no longer use this product?" If 40% or more of your users answer yes, you've found product-market fit. But getting to that number—and understanding what it really means—requires more than a single survey question.

What is Product-Market Fit?

Product-market fit is the degree to which your product satisfies strong market demand. It's the moment when customers start pulling your product into the market rather than you pushing it toward them.

Marc Andreessen famously described it: "You can always feel when product-market fit isn't happening. The customers aren't quite getting value out of the product, word of mouth isn't spreading, usage isn't growing that fast."

The challenge is that PMF isn't binary. It exists on a spectrum, and it can strengthen or weaken over time as markets evolve and competitors emerge. This is why measurement matters—you need to know where you stand and whether you're moving in the right direction.

The Sean Ellis Test Explained

Sean Ellis, who coined the term "growth hacking," developed the most widely used PMF survey question: "How would you feel if you could no longer use [product]?"

Respondents choose from three options:

• Very disappointed
• Somewhat disappointed
• Not disappointed

The 40% threshold comes from Ellis's analysis of successful startups. Companies where 40% or more of surveyed users said they'd be "very disappointed" consistently showed strong growth trajectories. Below 40%, growth was harder to sustain.

This question works because it measures emotional attachment, not just satisfaction. Users might be satisfied with a product they could easily replace. But if they'd be very disappointed to lose it, you've created something they genuinely need.

Beyond the 40% Benchmark

The 40% rule is a useful heuristic, but context matters:

• Sample composition: Are you surveying your most engaged users or a representative sample? Power users will skew higher; casual users will skew lower.
• Product category: Some categories naturally have higher switching costs and emotional attachment. A project management tool might hit 40% more easily than a utility app.
• Market maturity: In crowded markets with many alternatives, even 30% might indicate strong positioning. In nascent markets, you might need 50%+ to have real defensibility.
• Segment variation: Your overall score might be 35%, but one segment might be at 60% while another is at 15%. This tells you where to focus.

Don't obsess over hitting exactly 40%. Focus on the trend. Are you moving toward stronger PMF or away from it? What's driving the change?

When to Deploy PMF Surveys

Timing matters for PMF measurement. Survey too early and users haven't experienced enough value. Survey too late and you've missed the window to course-correct.

Key moments to measure PMF:

• Post-onboarding: After users have completed setup and used core features at least a few times
• After key milestones: When users hit usage thresholds that indicate meaningful engagement
• Before major pivots: Establish a baseline before making significant product changes
• After feature launches: Measure whether new capabilities strengthen or dilute PMF
• During fundraising prep: Investors increasingly ask for PMF data
• Quarterly or monthly: For ongoing tracking as part of your metrics dashboard

Avoid surveying users who haven't had enough exposure to form a meaningful opinion. A user who signed up yesterday can't tell you if they'd be very disappointed to lose your product.

Complementary Questions to Ask

The Sean Ellis question tells you whether you have PMF, but not why or how to improve it. Add these questions for actionable insights:

• "What is the primary benefit you receive from [product]?" — Reveals your actual value proposition from the customer's perspective
• "What type of person do you think would benefit most from [product]?" — Helps identify your ideal customer profile
• "How can we improve [product] for you?" — Surfaces specific enhancement opportunities
• "What would you likely use as an alternative if [product] were no longer available?" — Identifies your real competitors and substitutes
• "How did you discover [product]?" — Reveals which acquisition channels attract high-PMF users

Segment responses by the disappointment level. What do "very disappointed" users say about benefits versus "not disappointed" users? The differences reveal what drives PMF.

Building Continuous PMF Measurement

PMF isn't a milestone you achieve once and forget. Markets shift, competitors emerge, and customer expectations evolve. What created PMF last year might not sustain it next year.

Build PMF measurement into your regular feedback loops:

• Trigger-based surveys: Automatically survey users after they hit engagement milestones
• Cohort tracking: Compare PMF scores across signup cohorts to spot trends
• Segment analysis: Track PMF separately for different user types, plans, or use cases
• Correlation analysis: Connect PMF scores to retention, expansion, and referral metrics

The goal is to treat PMF as a leading indicator, not a lagging one. By the time retention metrics show problems, you've already lost users. PMF surveys can surface weakening fit before it shows up in churn data.

Tools like SenseFolks FastPoll and OpenFeedback make it easy to embed PMF questions at the right moments in your product. Combine quantitative PMF scores with qualitative feedback to understand not just where you stand, but what to do about it.

Remember: the opposite of feedback isn't praise—it's indifference. When users stop giving feedback, they've often given up on you. Keep the conversation going, and you'll have the insights you need to strengthen PMF over time.