How this calculator works
The net promoter score comes from one question: how likely are you to recommend us to a friend or colleague, on a scale from 0 to 10? Responses of 9 or 10 are promoters, 7 or 8 are passives, and 0 to 6 are detractors. Take the share of promoters, subtract the share of detractors and multiply by 100. Passives are counted in the denominator but not in either group, which is why the score can be negative. A score of +33 means promoters outnumber detractors by 33 percentage points. The number is widely used but it is not a scientific measurement. It moves with the wording of the question, the timing of the survey, the sample and the industry, and scores from one company are rarely comparable with another. It also throws away information: a business with 55% promoters and 20% detractors scores the same as one with 35% and 0%, even though the second has far fewer unhappy customers. Report the score next to the response rate, the sample size and the shares of each group, and treat a small change as noise rather than a signal. Surveys with a low response rate tend to over-represent the very happy and the very angry.
Formula
Promoter share = responses of 9 or 10 / total responses. Passive share = responses of 7 or 8 / total responses. Detractor share = responses of 0 to 6 / total responses. Net promoter score = (promoter share - detractor share) x 100. When shares are given directly, the three must add up to 100%.
Worked example
With scores 10, 9, 9, 8, 7, 10, 6, 9, 5, 10, 8, 9, 4, 10 and 7, there are 15 responses. Eight of them are 9 or 10, so the promoter share is 8 / 15 = 53.3%. Four are 7 or 8, a passive share of 26.7%, and three are 0 to 6, a detractor share of 20%. The score is (53.3 - 20) = 33.3.
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Frequently asked questions
Is a higher net promoter score always better?
Within one business tracked the same way over time, yes. Between businesses it is a weak comparison, because the survey method, the customer relationship and the industry all differ. Use it as a trend, not a league table.
Why are passives left out of the score?
The method was designed to separate enthusiastic customers from unhappy ones. Passives are counted in the denominator but not in either group, so a large passive group pulls the score toward zero.
Can the score be negative?
Yes, down to -100 when every response is a detractor. A score of zero means promoters and detractors are equally common.
How many responses do I need?
Enough that a small change is not just noise. For a small business a rolling window of a few hundred responses is a reasonable start; for a large one, several thousand. Always publish the sample size with the score.
Should I use the 0 to 10 scale or a 5-point scale?
The net promoter score is defined on the 0 to 10 scale. A 5-point scale cannot be converted into it without changing the definition, so keep the original question if you want to track NPS.