How to calculate NPS: formula, example and free calculator
NPS is simple to calculate: promoters minus detractors, in percentage. Here's the step-by-step with a numerical example and a free online calculator.
The NPS formula
The official Net Promoter Score formula is: NPS = % promoters − % detractors. Passives don't enter the formula directly, but they count in the total response base — which reduces the percentage weight of the other groups. The final result always sits between −100 (all detractors) and +100 (all promoters).
Step-by-step
Calculating NPS is straightforward. First, collect scores from 0 to 10. Then classify each response: 9 and 10 are promoters; 7 and 8 are passives; 0 to 6 are detractors. Next, calculate the percentage of promoters and the percentage of detractors over the total responses. Subtract one from the other and you have your NPS.
- ✓Collect 0–10 scores with the standard question
- ✓Classify: 9–10 promoters · 7–8 passives · 0–6 detractors
- ✓Compute % promoters and % detractors over the total
- ✓Subtract: % promoters − % detractors = NPS
Practical example
Imagine a survey with 200 responses. You have 120 promoters (60%), 40 passives (20%) and 40 detractors (20%). Applying the formula: NPS = 60 − 20 = 40. With an NPS of 40, you're in the "Good" zone — a healthy result with clear room to grow. If you had 30% detractors, the NPS would drop to 30. Small moves in the percentage base create big swings in the score — that's why NPS is a sensitive metric that needs a minimum number of responses to be reliable.
NPS benchmark zones
The result is interpreted across five reference zones used globally. Each zone gives an immediate diagnosis of the customer base's health.
- ✓Excellent: ≥ 70 — world class
- ✓Great: 50 to 69 — strong performance
- ✓Good: 30 to 49 — healthy result
- ✓Fair: 0 to 29 — caution
- ✓Risk zone: below 0 — critical
Common calculation mistakes
Three mistakes appear over and over. First: counting only positive answers and ignoring detractors — NPS needs the total response count as base. Second: taking the arithmetic mean of the scores — that's an average, not NPS, and it misses the essence of group classification. Third: calculating with too little volume — below 100 responses the number swings too much to reflect the actual base.
Frequently asked questions about NPS calculation
How many responses are needed to calculate NPS?
Technically, you can calculate with any number. But for the result to be statistically useful, aim for at least 100 responses per measurement period. Below that, the number oscillates too much with individual votes.
Do passives count in the calculation?
Not directly in the formula (which subtracts detractors from promoters), but they count in the total response base — reducing the percentage of the other two groups. More passives generally mean a lower NPS in absolute terms.
Can I calculate NPS in Excel?
Yes. The formula is straightforward: =(COUNTIF(range,">=9")/COUNTA(range) − COUNTIF(range,"<=6")/COUNTA(range))*100. But automating both collection and calculation saves hours a month and eliminates manual errors.
Does the NPS change if the total number of responses changes?
Yes. Since the calculation is percentage-based, every new response slightly alters the proportions. It's normal for the number to oscillate a bit between periods. Use consistent measurement windows (monthly, quarterly) to compare.
Is there a free online calculator?
Yes. Use our free NPS calculator — enter promoters, passives and detractors and see the result instantly, already classified by benchmark zone.
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