What is Product-Market Fit and how to measure it

Product-Market Fit is the point at which a product becomes not just useful but indispensable to a large enough group of users. Before that point, any growth is temporary: the team spends money acquiring people who don't stay. After it, growth starts to pay for itself, because users stick with the product and bring in others.

The problem is that PMF is an intuitive concept, while decisions have to be based on numbers. That's why there is a specific, measurable method: the test devised by Sean Ellis, Dropbox's first marketer. It sounds simple: ask the product's active users a single question — “How would you feel if you could no longer use this product?” — with the answer options “very disappointed,” “somewhat disappointed” and “not disappointed.” After analyzing a hundred startups, Ellis derived a threshold: if 40% or more of users answer “very disappointed,” the product has found its place in the market. Below that threshold, growth will be artificial and unstable.

An important nuance: you shouldn't ask everyone indiscriminately, only those who have actually tried the core of the product — for example, people who have used it at least twice in the past two weeks. That's exactly what the Superhuman team did: their first measurement showed just 22%. Instead of simply adding features, they started analyzing the answers of those who said “somewhat disappointed” — what exactly was holding them back from full loyalty — and deliberately closing those gaps. Over several quarters, the score rose from 22% to 58%.

And one more thing that is often forgotten: PMF is not a one-off box you tick and then forget about. The score needs to be tracked regularly and by segment, because when you target a new audience or expand your market, it can drop again — and that will be an early warning before your growth metrics sag.

Sources:

1. Sequoia Capital — The Arc Product-Market Fit Framework
2. Reforge — Measure and improve product/market fit with the 40% test
3. First Round Review — How Superhuman Built an Engine to Find Product Market Fit
4. Y Combinator Startup Library — How to Plan an MVP