Define Product-market fit beyond just feelings: Ask users how they would feel if your product disappeared. If 40% say "very disappointed," you have found it. This way, you define it as a number you can hillclimb.
Article: How Superhuman Built an Engine to Find Product-Market Fit
Marc Andreessen famously defined Product-Market Fit(PMF):
“You can always feel when product-market fit is not happening. The customers aren't quite getting value out of the product, word of mouth isn't spreading, usage isn't growing that fast, press reviews are kind of ‘blah,’ the sales cycle takes too long, and lots of deals never close.
And you can always feel product-market fit when it is 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. Money from customers is piling up in your company checking account. You're hiring sales and customer support staff as fast as you can. Reporters are calling because they've heard about your hot new thing and they want to talk to you about it. You start getting entrepreneur of the year awards from Harvard Business School. Investment bankers are staking out your house.”
Rahul Vohra turned it into a metric by asking users: "How would you feel if you could no longer use this product?" with a PMF threshold of 40% "very disappointed."
Superhuman started at 22%. But his first move wasn't to build anything. He segmented users to find which personas appeared most in the "very disappointed" group. By narrowing the target audience, the score jumped to 33% without a single product change.
Then he analyzed feedback to extract the product's core value: speed, focus, keyboard shortcuts. From users who are still on the fence to be "very disappointed", he identified blockers.
He split the roadmap 50/50: half doubling down on what fans loved, half removing barriers. And after three quarters of execution, Superhuman hit 58%.
In the four-step framework (segment users, find out what they love or hate, build for both, and keep going), most people skip over the segmentation part. However, you can improve your score without building anything new just by reorganizing who you're talking to. You then just need to find more of those people!