One question, three groups of people
NPS (Net Promoter Score) starts from one question: “How likely are you to recommend us to a friend or colleague?”, answered from 0 to 10. The answers do not count as numbers. They split people into three groups:
- Promoters (9-10): they would recommend you without being asked.
- Passives (7-8): satisfied, but they would switch for a better offer.
- Detractors (0-6): they would not recommend you, and may tell others not to come.
The detractor threshold is strict on purpose. A 6 out of 10 looks “fairly good”, but in NPS it counts the same as a 0: neither person would recommend you.
Percentage of promoters minus percentage of detractors
NPS = % promoters − % detractors
Passives are left out of the difference, but they count in the total, so in the denominator of each percentage. The result runs from −100 (all detractors) to +100 (all promoters), and is written as a whole number, not a percentage.
An example with 200 answers:
| Group | Answers | Share |
|---|---|---|
| Promoters (9-10) | 90 | 45% |
| Passives (7-8) | 60 | 30% |
| Detractors (0-6) | 50 | 25% |
| NPS | 200 | 45 − 25 = +20 |
Same average, different NPS
The most common mistake is to take the average of the scale (“average score 8.0”) and read it as NPS. Two surveys with ten answers each, all synthetic:
| Survey | Answers | Average | NPS |
|---|---|---|---|
| A | ten times 8 | 8.0 | 0 |
| B | six times 10, four times 5 | 8.0 | +20 |
In A nobody is a promoter: everyone is a passive, so NPS is 0. In B, 60% would recommend you and 40% would not. The average is the same, but the two companies have very different problems: the first excites nobody, the second has a group of customers leaving unhappy.
The same reason explains why NPS moves “oddly”. A customer going from 7 to 8 changes nothing. One going from 6 to 7 raises NPS, because they leave the detractors.
With few answers, one person changes the number
With 20 answers, each person is 5% of the total. If a single detractor had answered as a promoter, NPS would be 10 points higher. A “10 point drop” from one month to the next may be just one customer.
- Always write the count next to the NPS: “+20 from 200 answers” says far more than “+20”.
- Compare periods with enough answers. If a week has five, combine weeks into a month.
- Look at the trend over many periods, not the change between two.
In Sightelle, a week’s score is not shown when it has fewer than 5 ratings. An empty week is more honest than a number made by two people.
Five ways to get the wrong number
- An average instead of NPS. See section 3: the same average can give a very different NPS.
- A different scale. A “1 to 5” is satisfaction (CSAT), not NPS. The 9-10 and 0-6 thresholds only apply to the 0-10 scale, and two scales do not add up to one score.
- Averaging NPS across departments. If department A has +40 from 10 answers and B has 0 from 90, the overall NPS is not +20 but +4. Recalculate on all answers together.
- Asking only the people you know are happy. The number goes up, but it no longer describes your customers. The same goes for inviting public reviews only after a high score: Google and EU consumer law prohibit it.
- A number without a “why”. A falling NPS says something changed, not what. Without an open question after the score, you have nothing to fix.
The question after the score is the most useful one
Right after the score, add an open question tailored to the group: “What spoiled your experience?” for detractors, “What would make us better?” for passives, “What do you like most?” for promoters. Then read the answers and group them into themes: how many mention delivery, how many price, how many support.
With a few dozen answers this is done by hand. With hundreds every month, and with comments that also arrive from tickets or reviews, it becomes a full-time job.
How Sightelle does it
- It calculates NPS with the formula in this guide, and per week with the same threshold of 5 ratings.
- Every open answer becomes part of your themes, together with tickets and reviews, in your customers’ own words.
- A low score can open a recovery case with an owner and a deadline, if you turn on the rule.
Surveys and the analysis are included in the free audit too. See the surveys or upload a file with the answers you already have.
See the “why” in your own comments
A file of answers or tickets, a few minutes, one document for management.