How do I know if my D2C brand has actually reached product-market fit, or if I'm just imagining it from a few good sales days?
The short answer
Run the Sean Ellis 40% test on real repeat buyers, not first-time purchasers: ask "how would you feel if you could no longer buy [product]?" and see what percentage say "very disappointed." Above 40% is a strong signal you have something people genuinely need, not just tried once; below 25% means you're still iterating on the product or the audience, not scaling spend into it. Run this quarterly on a fresh cohort each time (never resurvey the same people) so you can see if the score is trending up as you fix things or quietly slipping as competitors catch up.
A quick summary to orient you. The real value is below: the resources worth your time, from people who've actually done it, not us.
Here are the resources
Hand-picked from around the web, each with a note on why it earns your time. India-specific ones carry a badge.
Why we picked it
A clear step-by-step on running the 40% test correctly - who to survey, when, and how to avoid the sampling mistakes (resurveying the same users, surveying first-timers) that make the score meaningless.
Why we picked it
The definitive short book on why customer conversations mislead founders and how to fix the questions you ask - used in accelerator curricula worldwide and directly applicable to a founder doing pre-launch interviews.
Why we picked it
The original Sean Ellis PMF survey, made freely usable - the fastest way to actually run the 40% test on your own repeat buyers instead of reading about it.
