What is product-market fit and how would you know if you have it?
Model answer
Model answerProduct-market fit is when your product solves a real problem for a real group of people so well that they'd be genuinely upset if it disappeared. The clearest signal is organic growth — users recommending your product without incentive. To measure it: Look at retention curves that flatten instead of dropping to zero. Check NPS above 40. But the most reliable single indicator is the Sean Ellis test: survey users with one question — 'How would you feel if you could no longer use this product?' If over 40% answer 'very disappointed,' you have strong product-market fit. It's not a hard cutoff, but a proven benchmark. No single metric confirms PMF — it's a pattern across all signals.
Framework · Product-Market Fit Signals Framework
- RMeasure retention behavior
Plot retention over time: Do users come back? A curve that drops to zero = no PMF. A curve that flattens at 30-50% = strong signal. The inflection point matters — if users stop returning within 2 weeks, product solves a one-time need, not ongoing value. - OTrack organic growth and word-of-mouth
Segment your users by source. What % came through referral or organic (not paid ads)? If organic/referral is >30% of new users, it signals strong product-market fit. Users won't refer a mediocre product, so word-of-mouth is the truest indicator of real value. - NCalculate Net Promoter Score (NPS)
Ask: "How likely are you to recommend this to a friend?" Score 0-10. Promoters (9-10) minus Detractors (0-6) = NPS. For PMF: target NPS >40. Why? NPS >40 correlates with companies that grow. It's not perfect, but combined with other signals, NPS >40 is a reliable pattern. - EDeploy the Sean Ellis test
Survey users: "How would you feel if you could no longer use this product?" Options: Very disappointed / Somewhat disappointed / Not disappointed. Count % who say "very disappointed." >40% = strong PMF. Why 40%? Sean Ellis analyzed 100+ startups. He found that founders of fast-growing companies reported >40% "very disappointed" responses, while struggling companies were <40%. This 40% threshold emerged as a consistent PMF predictor across different industries and product types.
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