Free product-market fit survey response calculator
Foundable Product-Market Fit Survey Calculator and Scorecard
Calculate a directional product-market fit survey result, then review separate supporting behavior before deciding what to test next.
One declared scoring rule, with uncertainty shown.
This calculator divides “Very disappointed” by all completed responses: “Very disappointed,” “Somewhat disappointed,” “Not disappointed,” and “No longer use the product.” Blank or skipped responses do not count.
The calculator compares the observed response proportion with the commonly cited 40% reference line and adds a Wilson 95% interval around that proportion. The reference is an experience-based heuristic, not a proof, certification, or forecast.
A 40% observed share still carries uncertainty.
Twenty “Very disappointed,” 20 “Somewhat disappointed,” 10 “Not disappointed,” and zero “No longer use” responses produce 20 ÷ 50 = 40.0%.
The Wilson 95% interval is 27.6%–53.8%, so it crosses the 40% line. The observed share is exactly at the reference line while the interval spans both sides. Neither statement means product-market fit passed or failed.
Survey recent real users, then check behavior.
For the closest match to Sean Ellis's original guidance, survey people who experienced the core offering, used it at least twice, and used it within the prior two weeks. Only call the sample random when selection was actually random.
Method sources: Sean Ellis's original product-market-fit survey guidance and NIST's Wilson interval method. The all-completed denominator is visible in an archived Survey.io result. Sean Ellis did not sponsor, review, or endorse this calculator. Use the result alongside retention, repeat use, referrals, and payment evidence.
Document supporting behavior separately from the survey result.
The survey question and roughly 40% benchmark adapt a heuristic described by Sean Ellis in 2009. Foundable divides very disappointed responses by all four completed response categories, itemizes no-longer-use responses, and adds a Wilson 95% interval. Treat the result as a directional snapshot of respondents, not proof of product-market fit, retention, growth, or business success. Sean Ellis did not sponsor, review, or endorse this calculator.
This checklist is Foundable's separate planning framework, not a validated scale. Check only documented signals; the total does not change the survey percentage or prove product-market fit.
Turn PMF evidence into the next Foundable move.
Define the eligible respondent group
Use participants who experienced the core offering, used it at least twice, and used it within the prior two weeks. Call the sample random only when selection was actually random.
Keep the denominator explicit
Count very disappointed, somewhat disappointed, not disappointed, and no longer use in the completed-response denominator. Itemize the no-longer-use count beside the percentage.
Read the interval with the point estimate
Use the Wilson 95% interval to show sampling uncertainty. With a small completed-response sample, the interval can span both sides of the 40% reference line.
Compare stated intent with behavior
Review retention, repeat use, payment, referral, switching, objections, and segment quality separately before choosing a product or growth experiment.
Answers to common questions about this tool.
How do I calculate a product market fit score?
Foundable calculates the product-market-fit survey result as very disappointed responses divided by all completed responses: very disappointed, somewhat disappointed, not disappointed, and no longer use. It itemizes no-longer-use responses and shows a Wilson 95% interval around the completed-response share. The survey question and roughly 40% benchmark adapt a heuristic described by Sean Ellis; Foundable adds the interval and explicit calculation display. The benchmark is directional, not proof of product-market fit, retention, growth, or business success. Sean Ellis did not sponsor, review, or endorse this calculator.
How does the product-market fit survey calculator work?
Enter the counts for very disappointed, somewhat disappointed, not disappointed, and no longer use. Foundable divides very disappointed by all four completed response categories, itemizes no-longer-use responses, and shows a Wilson 95% interval.
How should I interpret the 40% product-market fit benchmark?
Treat roughly 40% as a directional survey benchmark described by Sean Ellis, not a pass/fail proof. Read the point estimate with its Wilson 95% interval, respondent eligibility, sampling method, retention, and commercial outcomes.
Which responses count in the PMF survey percentage?
Foundable includes very disappointed, somewhat disappointed, not disappointed, and no longer use in the completed-response denominator. It also itemizes the no-longer-use count so the point estimate does not hide it.
What evidence should I review alongside the PMF survey result?
Review retention cohorts, repeat use, referrals, payment evidence, switching behavior, activation, objections, segment quality, and repeated reach through a channel. A survey response share alone does not prove product-market fit.
What does the supporting evidence score measure?
Foundable's separate checklist records twelve equally weighted planning signals. It is not a validated scale, does not change the survey result, and should be read as a prompt for evidence review rather than a product-market fit verdict.