Hong Life CalculatorsUnderstanding the Net Promoter Score calculator — concept and principle
The Net Promoter Score (NPS) is a customer loyalty measure built on one question: "How likely are you to recommend us to a friend or colleague?", answered on a 0–10 scale. Companies use it to track customer sentiment over time, compare teams or products, and follow up with unhappy customers. Enter how many people gave each type of answer and the calculator returns the score and the share of each group.
How it is calculated
Respondents are grouped by their answer:
- Promoters: 9 or 10.
- Passives: 7 or 8.
- Detractors: 0 to 6.
NPS = (promoters − detractors) ÷ total respondents × 100, which is the same as % promoters − % detractors. Passives count in the total but do not add or subtract. The score ranges from −100 (everyone a detractor) to +100 (everyone a promoter) and is shown as a number, not a percentage.
The principle
Fred Reichheld, with Bain & Company and Satmetrix, introduced NPS in 2003, arguing that willingness to recommend is a strong signal of loyalty and future growth. Subtracting detractors from promoters rewards enthusiastic customers and penalises unhappy ones, who may leave and discourage others. Passives are treated as satisfied but not loyal, so they dilute the score without changing its sign.
Worked example
- Promoters = 220, passives = 120, detractors = 60; total = 400.
- % promoters = 220 ÷ 400 = 55%.
- % detractors = 60 ÷ 400 = 15%.
- NPS = 55 − 15 = 40.
How to read the result
Any score above 0 means more promoters than detractors. Typical scores differ a lot between industries and countries, and between relationship surveys (sent periodically) and transactional surveys (sent after a purchase or support call), so compare mainly with your own previous results and with competitors measured the same way. With small samples the score moves a lot by chance; a change of a few points on 50 responses may be noise.
Common mistakes
- Averaging the 0–10 answers instead of counting groups.
- Reporting NPS as a percentage ("40%") rather than a score.
- Surveying only happy customers, or only after positive interactions.
- Changing the question wording or scale and comparing with old results.
Frequently asked questions
Is a score of 40 good?
It means promoters outnumber detractors by 40 points, which is positive. Whether it is strong depends on your industry and survey type, so compare like with like.
Why are 7 and 8 ignored?
They are counted in the total but are not promoters or detractors. Passives are seen as satisfied but not enthusiastic.
How many responses do I need?
There is no fixed minimum, but the fewer responses you have, the more the score swings by chance. Track trends over larger samples.
Can NPS be negative?
Yes. If detractors outnumber promoters, the score falls below zero, down to −100.
Sources: Reichheld, F. F. (2003). The One Number You Need to Grow. Harvard Business Review, 81(12).