Product-Market Fit: How to Know When You've Found It (With Real Examples)

Marc Andreessen defined product-market fit as 'being in a good market with a product that can satisfy that market.' But how do you actually measure it?

The Sean Ellis Test

Survey your users: 'How would you feel if you could no longer use this product?' If 40%+ say 'very disappointed,' you likely have PMF. If it's below 40%, you have work to do.

Quantitative Signals of PMF

• Net Promoter Score (NPS) > 50: Users love the product enough to recommend it
• Week-over-week organic growth: People are finding you without paid acquisition
• Low churn (<5% monthly for SMB SaaS): Users stay because the product is essential
• High engagement: Users return frequently and complete the core action repeatedly

Qualitative Signals of PMF

• Users get visibly frustrated when the product is down
• Customers start recommending your product without being asked
• You're struggling to keep up with inbound demand
• Sales cycles are shortening naturally

Real Examples

Slack: Before PMF, it was a gaming company pivot. Once they found PMF, they grew from $0 to $7M ARR in their first year.

Notion: Spent years quietly iterating. Then went viral organically, adding millions of users without paid marketing.

What PMF Is NOT

• High signups (vanity metric)
• Press coverage
• App Store rankings
• Revenue from friends and family

The Bottom Line

PMF feels unmistakable. Before you have it, growth feels like pushing a boulder uphill. After you find it, it feels like the market is pulling you forward.