How is Net Promoter Score (NPS) calculated?

How is Net Promoter Score (NPS) calculated?

Net Promoter Score (NPS) is a whole number from -100 to +100, where +100 is the best score, simply put it is calculated as the % Promoters minus the % Detractors.  Here's the formula:

NPS = [ (Promoters - Detractors) / Total NPS Respondents ] x 100

Here are some examples:

-100 NPS: 0 Promoters, 0 Passives, 50 Detractors
NPS = (0 - 50) / 50 x 100

+100 NPS: 50 Promoters, 0 Passives, 0 Detractors
NPS = (50 - 0) / 50 x 100

+41 NPS: 50 Promoters, 20 Passives, 15 Detractors
NPS = (50 - 15) / 85 x 100