NPS and CSAT calculator
Enter how many people gave each score, or paste a column of scores. You get your NPS or CSAT, the margin of error at 95% and how many responses you need for the precision you want.
Net Promoter Score (0 to 10)
Your NPS
Enter at least one response to see a score.
26on a scale from −100 to 100
- Promoters
- 46% (46)
- Passives
- 34% (34)
- Detractors
- 20% (20)
- Responses
- 100
- Margin of error at 95%
- ±15.1 points
- Likely range
- 11 to 41
For ±5 points you’d need about 911 responses with this spread of scores.
With fewer than 30 responses, treat the margin of error as rough.
NPS 26, margin of error ±15.1 points, from 100 responses.
Customer satisfaction (CSAT) (1 to 5)
Your CSAT
Enter at least one response to see a score.
80%satisfied: a 4 or 5
- Satisfied
- 80% (80)
- Not satisfied
- 20% (20)
- Average score
- 4.1 out of 5
- Responses
- 100
- Margin of error at 95%
- ±7.8 points
- Likely range
- 72.2% to 87.8%
For ±5 points you’d need about 246 responses at this level of satisfaction.
With fewer than 30 responses, treat the margin of error as rough.
CSAT 80%, margin of error ±7.8 points, from 100 responses.
The formulas
Net Promoter Score
NPS asks how likely someone is to recommend you, on a scale from 0 to 10. A 9 or 10 is a promoter, a 7 or 8 a passive and 0 to 6 a detractor. NPS = % promoters − % detractors, a number from −100 to 100. Passives only count toward the total number of responses.
For the margin of error, score every promoter +1, every passive 0 and every detractor −1. NPS is the average of those scores × 100. Their spread (variance) is P + D − (P − D)², with P and D as fractions. The margin of error at 95% is 1.96 × √(variance ÷ n) × 100 points.
An example: 100 responses, 46 promoters and 20 detractors. NPS is 26, the variance is 0.46 + 0.20 − 0.26² = 0.59 and the margin is 1.96 × √(0.59 ÷ 100) × 100 ≈ 15 points. The real NPS is likely between 11 and 41.
Customer satisfaction (CSAT)
CSAT here is the share of satisfied answers: a 4 or 5 on a scale from 1 to 5, divided by all answers. The calculator also shows the average score, because some teams report that instead.
The margin of error is 1.96 × √(p × (1 − p) ÷ n), with p the satisfied share. 80 satisfied out of 100: 1.96 × √(0.8 × 0.2 ÷ 100) = 7.8 percentage points.
How many responses you need
For a margin E (as a fraction) you need n = 1.96² × variance ÷ E² responses. For CSAT the variance is p × (1 − p). The calculator uses the spread of the answers you entered. Without data yet, plan for the worst case: a variance of 1 for NPS and 0.25 for CSAT. That gives 1,537 responses for ±5 NPS points and 385 for ±5 CSAT points.
What it assumes
- Responses are a random sample of your customers. People who answer a survey can think differently from people who don’t, and no formula corrects for that.
- The margin uses the normal approximation. With fewer than about 30 responses, or when nearly everyone gives the same answer, treat it as rough.
- It leaves out the finite population correction. If you surveyed a large share of all your customers, the real margin is a little smaller.
- When you compare two periods and their ranges overlap, the difference may be chance.
Questions about NPS and CSAT
How do you calculate NPS?
Subtract the percentage of detractors (0 to 6) from the percentage of promoters (9 and 10). With 46% promoters and 20% detractors, NPS is 26. Passives (7 and 8) only count toward the total.
How do you calculate CSAT?
Divide the number of satisfied answers (4 or 5 on a scale from 1 to 5) by all answers and multiply by 100. 80 satisfied answers out of 100 give a CSAT of 80%.
How many responses do I need for a reliable NPS?
That depends on the precision you want and on how your answers are spread. In the worst case, ±10 points takes 385 responses and ±5 points takes 1,537. The calculator works it out for your own spread of scores.
What does the margin of error mean?
If you ran the same survey many times with other random customers, about 95 out of 100 of those ranges would contain your real score. An NPS of 26 ± 15 means the real NPS is likely somewhere between 11 and 41.
Can I paste scores from a spreadsheet?
Yes. Copy the column with scores and paste it in. Every whole number from 0 to 10 (or 1 to 5 for CSAT) counts as one response, and headers and empty cells are skipped. The scores stay in your browser.
In Flagbell
Live chat
A fast, light chat widget for your site, without trackers or cookies. Outside office hours, Flagbell emails your customer back in the same conversation.
About live chat →Inbox
All support email from all your brands in one calm inbox, with a brand filter, saved replies in two languages, a calendar and GDPR deadlines.
About the inbox →Help center
A fast, static help center for every brand on its own subdomain, managed centrally in Flagbell. The chat widget shows matching articles before the chat.
About the help center →Read next
Guide
Writing saved replies
How to write saved replies that don’t sound canned: which questions first, structure, placeholders, tone, two languages and four templates to copy.
Read the guide →Free tool
Reply templates
39 free customer service reply templates for refunds, late orders, bugs, billing and logins. Fill in your brand and names once, then copy them.
Open the tool →Free tool
Staffing calculator
Free Erlang C calculator for chat and email support. Work out agents on the floor and rostered, with chat concurrency, shrinkage and service level.
Open the tool →A rating at the end of every chat.
In Flagbell, your visitor can rate a chat when you mark it Done. Flagbell is a helpdesk with live chat, a shared inbox and a help center for every brand. It’s in development: join the waitlist to hear when you can use it.