If 40% of Your Customers Won’t Freak Out Without Your Product, You’re in Trouble

How to apply Sean Ellis’s 40% rule to measure true demand and avoid wasting money on a product nobody really needs.

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One of the fastest ways to tell if you’re building something people actually want?
Ask your users one simple question:

👉 “How would you feel if you could no longer use our product?”

This question forms the core of the 40% Rule, a concept developed by Sean Ellis, the growth expert behind Dropbox and LogMeIn.

At Smartware Advisors, we use this test with founders to quickly cut through the noise and get to the truth:
Are you solving a problem people care about—or just building something they can live without?

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Why This One Question Can Save You Thousands

Most early-stage startups are burning cash chasing traction—spending on marketing, hiring, or building more features—without knowing if the product actually matters to customers.

The 40% rule offers a fast, inexpensive way to check if you’re on the right path.

According to Sean Ellis:

“If at least 40% of users say they'd be very disappointed if they could no longer use your product, you're likely on your way to Product-Market Fit.”

Why 40%? Because anything less means your product is not essential—and users are just dabbling, not depending.

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How to Run the 40% Survey (The Simple Way)

🔧 Step 1: Identify your most active users

• These can be paid or unpaid users, but focus on those who are actually using the product regularly.

📩 Step 2: Send the survey

Ask the following question:

“How would you feel if you could no longer use [Product Name]?”
Options:

• Very disappointed
• Somewhat disappointed
• Not disappointed

Optional follow-up questions:

• What would you use as an alternative?
• What’s the biggest benefit you get from our product?
• Who do you think would benefit most from this product?

📊 Step 3: Analyze the results

• If 40%+ say “Very disappointed” → You’re on the right track.
• If it’s below 40% → You’re likely missing the mark on product-market fit.

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What to Do With the Results

✅ If You’re Above 40%

Congrats—you’re probably solving a real, painful problem.
Now:

• Double down on your top user segment.
• Use their feedback to refine your messaging, features, and positioning.
• Prepare to scale—but carefully.

❌ If You’re Below 40%

This is a wake-up call—not a failure.
It means:

• You may be solving the wrong problem.
• Or you’re targeting the wrong audience.
• Or your product isn’t yet strong enough to matter.

What to do next:

• Talk to users who selected “Somewhat disappointed” and find out why.
• Identify any patterns in your data (specific industries, job roles, use cases).
• Narrow your focus and consider pivoting your value proposition or audience.

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Real Talk: Most Startups Score Below 40% at First

And that’s okay.
The point of the 40% rule isn’t to make you feel good—it’s to keep you honest.

We’ve worked with startups that thought they had traction—users were signing up, revenue was growing—but when we ran the 40% survey, only 18% would have cared if the product disappeared.

That’s not product-market fit.
That’s temporary attention.

And attention fades.

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Final Takeaways: The 40% Rule = A Reality Check

If your product vanished tomorrow…
Would your customers freak out?
Or would they just… move on?

If it’s the latter, you need to dig deeper. Talk to customers. Tighten your focus. Rebuild your offer around a problem that hurts enough to solve.

At Smartware Advisors, we help founders test for PMF before they waste money scaling something the market doesn’t need.

💡 If you’re not sure your product is essential, the 40% rule will tell you.

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TL;DR – The 40% Rule in a Nutshell

✅ Ask your users: “How would you feel if you couldn’t use this product?”
📊 40%+ saying “Very disappointed” = product-market fit is likely
🔍 Less than 40% = time to revisit your audience, offer, or product
🚀 Don’t scale until the numbers—and your users—tell you it’s time

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Still guessing if you’re building something essential?
Run the 40% test. Or reach out—we’ll help you figure it out before it costs you. Reach out to Smartware Advisors for a free consultation  https://calendly.com/waqar-hashim.