NPS asks customers, on a 0 to 10 scale, how likely they are to recommend the product. Scores of 9 to 10 are 'promoters', 7 to 8 are 'passives', and 0 to 6 are 'detractors'. NPS = % promoters − % detractors, expressed as an integer between −100 and +100.
The metric is loved for its simplicity and criticized for its statistical fragility. A high NPS does not always correlate with growth; a low NPS in a growing company can reflect rapid expansion to less-satisfied segments. Use NPS as one signal, not the signal.