Product-Market Fit: 25 Signs You Have It + The Complete Measurement Checklist

Product-market fit is the most discussed and most misunderstood concept in startup land. Everyone claims they're "working toward PMF." Fewer people can articulate what it actually looks like, how to measure it, and — most importantly — what to do when you don't have it yet. This guide cuts through the noise. It gives you the Sean Ellis framework, the key metrics, and a concrete 25-point checklist you can run against your product today. TL;DR The 40% rule: If 40%+ of your users say they'd be "very disappointed" without your product, you likely have PMF — below that, you don't Retention is the ultimate test: If your week-4 retention curve flattens, you have PMF; if it keeps declining to zero, you don't Organic growth is the clearest signal: When users tell other people without being asked, something is working PMF is not binary: It exists on a spectrum, and you can have it in one segment before finding it in another Don't scale before PMF: Scaling a leaky bucket just empties your bank ac