Methodology: Net Promoter Score (NPS) Calculator

1. Scope

Calculates NPS from promoter (9–10), passive (7–8), and detractor (0–6) counts and provides benchmark context. It is not a customer-satisfaction model and does not causally link NPS to revenue.

2. Inputs and outputs

Inputs

promoters number
passives number
detractors number

Outputs

nps

(promoters − detractors) / total × 100.
sampleSize

Sum of all three groups.
distribution

Percentage of each bucket.

Engine source: src/lib/net-promoter-score-calculator/engine.ts

3. Formula / scoring logic

total     = promoters + passives + detractors
nps       = ((promoters - detractors) / total) * 100

4. Assumptions

Respondents are a random sample of customers. Survey-response bias (happy/angry customers respond more) is not corrected.
The 0–6 / 7–8 / 9–10 buckets are the Reichheld-standard definitions.

5. Data sources

Reichheld, The One Number You Need to Grow, Harvard Business Review, 2003 as of 2003

6. Known limitations

NPS-to-growth correlation is disputed in the academic literature. See Keiningham et al. (2007) "A Longitudinal Examination of Net Promoter and Firm Revenue Growth" — Journal of Marketing — for a methodologically critical view.
Small samples (< ~200) produce unstable NPS. Use confidence intervals, not point estimates.
Cross-industry benchmarks are noisy; within-vertical peer comparisons are more informative.

7. Reproducibility

Input
promoters = 60, passives = 25, detractors = 15.

Expected output
total = 100, nps = 45, distribution = 60% / 25% / 15%.

8. Change log

2026-04-24 methodology page first published.