What Net Promoter Score Measures and How to Calculate It
Net Promoter Score (NPS) is a single number that tells you how likely your customers are to recommend you to others. You calculate it by asking one question, sorting answers into three groups, and running a straightforward math formula. The result ranges from −100 to +100, and higher is better.
The question you ask is: "On a scale of 0 to 10, how likely are you to recommend us to a friend or colleague?" The answers fall into three categories: Promoters (9–10), Passives (7–8), and Detractors (0–6). You then subtract the percentage of Detractors from the percentage of Promoters to get your NPS.
Unlike customer satisfaction surveys that ask multiple questions, NPS strips the measurement down to one metric. This makes it fast to calculate and straightforward to track over time. Many businesses use it alongside other measures, but NPS alone tells you whether your customer base is growing or shrinking in loyalty.
Key Takeaways
- Ask customers one question on a 0–10 scale: "How likely are you to recommend us?"
- Sort responses into Promoters (9–10), Passives (7–8), and Detractors (0–6).
- Calculate NPS by subtracting the percentage of Detractors from the percentage of Promoters.
- An NPS above 50 is considered excellent; 0–30 is typical for most industries; negative scores mean more detractors than promoters.
- Track NPS over time to spot trends, and always ask a follow-up question to understand why customers gave their score.
The Three Customer Groups and What They Mean
Promoters are customers who answer 9 or 10. They are satisfied enough to recommend you and are likely to stay loyal. They may also spend more money with you over time and forgive occasional mistakes because they trust you.
Passives are customers who answer 7 or 8. They are satisfied but not enthusiastic. They will not actively recommend you, but they will not actively warn others away either. They are vulnerable to switching if a competitor offers something better.
Detractors are customers who answer 0 to 6. They are unhappy and likely to tell others about their bad experience. Detractors can damage your reputation and make it harder to attract new customers. Understanding why they are unhappy is often more valuable than understanding why Promoters are happy.
Step-by-Step Calculation With a Real Example
Suppose you survey 100 customers. Here is how to calculate your NPS:
- Count how many gave each score (0–10).
- Add up the 9s and 10s. Let's say you have 50 Promoters.
- Add up the 0s through 6s. Let's say you have 20 Detractors.
- Ignore the 7s and 8s (Passives) in the calculation.
- Divide Promoters by total respondents: 50 ÷ 100 = 50%.
- Divide Detractors by total respondents: 20 ÷ 100 = 20%.
- Subtract: 50% − 20% = 30 NPS.
Your NPS is 30. This is a solid score for most industries. If you had 60 Promoters and 10 Detractors out of 100, your NPS would be 50, which is considered excellent.
The formula works the same way whether you survey 50 people or 5,000. The percentage calculation automatically scales. Always include the total number of respondents when you report your NPS, because an NPS of 30 from 100 responses means something different than an NPS of 30 from 10 responses.
When and How Often to Measure NPS
You can send your NPS survey after a customer interaction—right after they buy, after they use support, or after they complete a project. Timing matters because customers are most likely to answer when the experience is fresh.
Some businesses measure NPS once a quarter, others monthly, and some continuously. Monthly or quarterly is common because it gives you enough responses to spot real trends without being so frequent that you annoy customers. If you measure too often, response rates drop and your data becomes unreliable.
Always pair the NPS question with a follow-up: "What is the main reason for your score?" This open-ended answer tells you what to fix. A Detractor who says "your website is confusing" is more useful than a Detractor score alone.
Interpreting Your NPS Score
NPS scores vary by industry, so context matters. A score of 50 is excellent in most sectors, but software companies often see scores above 60. A score of 0 to 30 is typical and means you have room to improve. A negative score means you have more Detractors than Promoters, which signals serious problems.
The real value of NPS is tracking it over time. If your score was 25 last quarter and 30 this quarter, you are moving in the right direction. If it dropped from 35 to 28, something changed—either you made a mistake or a competitor improved. Use the follow-up comments to find out which.
Comparing your NPS to competitors is tempting but risky. You do not always know how they calculated theirs, and different industries have different baselines. Focus instead on your own trend and on the reasons customers give for their scores.
Common Mistakes When Calculating NPS
The most common error is including Passives in the calculation. NPS uses only Promoters and Detractors; Passives are ignored. If you accidentally add or subtract the Passive percentage, your score will be wrong.
Another mistake is surveying too small a sample. If you ask only 5 customers and 2 are Promoters and 1 is a Detractor, your NPS is 20. But that number is fragile—one more Detractor response would drop it to 0. Aim for at least 30 responses per survey round to get a stable number.
A third mistake is asking the NPS question in isolation. Without the follow-up "Why?", you know your score but not what to do about it. The follow-up comments are often more valuable than the number itself.
Tools and Spreadsheets for Tracking NPS
You can calculate NPS in a spreadsheet using a straightforward formula. Create columns for each score (0–10), count the responses in each, then use a formula to calculate the percentages and subtract. Many survey tools like Typeform, SurveyMonkey, and Qualtrics calculate NPS automatically when you set up the question.
If you measure NPS regularly, a spreadsheet or dashboard that tracks the score over time is worth the setup. Plot your NPS on a line graph month by month so you can see trends at a glance. Add a column for the top reasons customers gave in their follow-up comments, so you can see whether the same problems keep appearing.
For teams that measure NPS across different departments or customer segments, a shared spreadsheet or straightforward dashboard prevents confusion about which number is current and how it was calculated.
Frequently Asked Questions
What is a good NPS score?
Scores above 50 are considered excellent. Scores between 0 and 30 are typical for most industries and mean you have loyal customers but also room to improve. Negative scores signal that more customers are unhappy than happy. Always compare your score to your own past performance and to your industry average, not to unrelated businesses.
Do I have to ask exactly 100 customers?
No. You can survey any number of customers, but aim for at least 30 responses per survey round so your score is stable. Smaller samples are noisier—one or two extra responses can swing your score significantly. Larger samples give you more confidence that your score reflects reality.
Can NPS be negative?
Yes. If you have more Detractors than Promoters, your NPS will be negative. For example, if 30% are Promoters and 40% are Detractors, your NPS is −10. Negative scores are rare in healthy businesses but signal serious customer dissatisfaction that needs when ready attention.
Should I measure NPS for every customer or just a sample?
Sampling is standard. Surveying every customer is expensive and exhausting for them. Instead, send the survey to a random sample after each transaction or on a regular schedule. A sample of 50–100 customers per month gives you reliable data without overwhelming people.
How do I improve my NPS?
Read the follow-up comments from Detractors and Passives to find patterns. If multiple customers mention slow support, hire more support staff or improve response times. If they mention a confusing product, simplify it. Track your NPS monthly to see whether your changes are working. Small improvements compound over time.