founder-strategy
What is product-market fit and how do you know when you have it?
Product-market fit (PMF) is the degree to which your product satisfies strong market demand. Signs include rapid organic growth, high retention, and customers who'd be 'very disappointed' without your product.
Product-market fit is one of the most important concepts in startup building — and one of the hardest to precisely define. Marc Andreessen famously described it as: '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... And you can always feel product-market fit when it's happening. The customers are buying the product just as fast as you can make it — or usage is growing just as fast as you can add more servers.'
How to measure PMF:
The Sean Ellis test: Survey your active users — 'How would you feel if you could no longer use this product?' If 40%+ say 'very disappointed,' you likely have product-market fit.
Retention curves: Plot what percentage of users are still active 1, 3, 6, 12 months after signing up. If the curve flattens (rather than declining to zero), you have a core user base with genuine need.
Net Promoter Score (NPS): A high NPS (above 50 is excellent) indicates customers are actively recommending your product.
Organic growth: Is word-of-mouth driving significant new users? Are you getting inbound interest without heavy marketing?
Churn: Low voluntary churn is the ultimate PMF signal. If customers stay, they're getting value.
Why it matters for fundraising: VCs invest in product-market fit signals more than anything else at the early stage. Showing that real customers with real pain are paying for and returning to your product is the most powerful thing you can show an investor.
Related glossary terms
Related questions
What startup metrics do VCs care about most?
VCs focus on growth rate, revenue, burn rate, CAC/LTV, churn, and net dollar retention — the specific metrics depend on the stage and business model.
How do VCs evaluate startups?
VCs evaluate startups on team quality, market size, product differentiation, traction, and whether the opportunity can return the fund — often summarized as 'team, market, product.'
What is the Rule of 40 for SaaS companies?
The Rule of 40 states that a healthy SaaS company's growth rate plus profit margin should equal at least 40%, balancing growth and profitability.