NPS and CSAT calculator, with the margin of error
Enter your response counts or paste the raw scores. You get the score, how much it could move by chance, and how many responses you'd need before a change means something.
25% promoters minus 30% detractors. With this many responses, the true score is probably somewhere between −34.4 and +25.7.
About 1,537 responses, in the worst case. NPS needs about four times as many responses as a satisfaction percentage for the same margin.
Ranges are 95% intervals: Wilson for percent satisfied, adjusted Wald (Rocks, 2016) for NPS, and the usual t-style interval for the average. The response planner uses the simpler normal approximation. All of them assume the people who answered are a fair sample of everyone, and they usually aren't: people with strong opinions answer more often. Your numbers stay in your browser.
Why the margin matters more than the score
Twenty responses can give an NPS of −5 whose 95% range runs from about −34 to +26. That range covers a team customers love and one they're quietly leaving. The score isn't wrong; it just can't tell those apart yet.
The fix is rarely a better survey. It's more responses over a longer window, the same question asked the same way, and a habit of reporting the response count next to the number.
What the calculator can't fix
- Who answers. Happy and angry customers reply more often than the indifferent middle.
- When you ask. A rating right after a solved problem reads higher than one a month later.
- Comparing tools. One tool's 4.3 average and another's 85% satisfied are different numbers.
- Small samples. Below about 30 responses, the margins here are only a rough guide.
For when to send which survey, plus 14 question templates, read CSAT vs NPS. For the rest of your scorecard, see customer support metrics.
Frequently asked questions
How is NPS calculated?
Ask how likely a customer is to recommend you on a 0 to 10 scale. Scores of 9 and 10 are promoters, 7 and 8 are passives, and 0 to 6 are detractors. NPS is the percentage of promoters minus the percentage of detractors, so it runs from −100 to +100. Passives count toward the total but not toward either side.
How is CSAT calculated?
There's no single standard. Many tools report the percentage of customers who chose 4 or 5 on a 5-point scale. Some report only 5s (top box), and some, including Talvo, report the average rating. The calculator shows all three from the same ratings, so you can see how far apart they are.
What is a good NPS or CSAT score?
It depends on your industry, your survey method and when you ask, so a number from another company's report rarely compares cleanly with yours. The more useful question is whether your own score is moving by more than its margin of error. Track the same survey, asked the same way, over time.
What does the margin of error mean?
It's a 95% range for where the score would land if you could ask every customer instead of the ones who answered. A score of +20 with a range of +5 to +35 means the real figure is probably somewhere in there. If two months' ranges overlap heavily, the change may be noise. The calculator uses the Wilson interval for percent satisfied and the adjusted Wald interval from Rocks (2016) for NPS, which stay sensible with small samples.
How many survey responses do I need?
For a percentage like CSAT within about ±5 points, plan on roughly 385 responses in the worst case. NPS is noisier: the same ±5 points needs about 1,540. Small teams usually can't reach those numbers each month, so report the response count next to every score and look at trends over a quarter.
Is my data sent anywhere?
No. The calculation runs in your browser, and the scores you type or paste aren't uploaded or stored.
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