NPS (Net Promoter Score) is the single most widely used metric for measuring customer loyalty. It is calculated from one simple survey question, but the calculation itself has subtleties — the scale, the cutoffs, how to handle passives, and how big the sample needs to be. This guide walks through every step and ends with a free NPS calculator you can paste your data into.

The NPS formula

The NPS formula is:

NPS = % Promoters − % Detractors

Passives are deliberately excluded from the formula. They do not add to or subtract from the score, but they should still be tracked — converting passives into promoters is the cheapest way to grow NPS.

The result is a single number on a scale from −100 (every respondent is a detractor) to +100 (every respondent is a promoter). Most organisations land somewhere between −20 and +60 depending on industry.

How to calculate NPS step-by-step

Ask the recommendation question. The classic phrasing is "How likely are you to recommend [organisation/product] to a friend or colleague?" Respondents answer on a 0-10 scale (the original Bain & Company standard) or 1-100 (the higher-resolution scale used by kazva.bg).
Classify every response. Each respondent falls into one of three buckets based on their score.
Calculate the percentage in each bucket. Divide the count of promoters by the total number of responses, multiply by 100. Do the same for passives and detractors.
Apply the formula. Subtract the detractor percentage from the promoter percentage. That difference is your NPS — between −100 and +100.

The 0-10 scale vs the 1-100 scale

Two scales are in common use. The classic 0-10 scale categorises responses as follows:

Promoters: 9-10
Passives: 7-8
Detractors: 0-6

The kazva.bg platform uses an extended 1-100 scale that captures finer differences in sentiment and reduces the "ceiling effect" common in 0-10 surveys:

Promoters: 80-100
Passives: 50-79
Detractors: 1-49

Both scales produce a comparable NPS in the −100 to +100 range. The wider scale is more sensitive — small improvements in customer experience show up as visible movement in the score, rather than getting absorbed by the coarse 0-10 buckets.

A worked example

Imagine you surveyed 200 customers after a service visit and got the following responses:

120 respondents scored 9 or 10 (promoters)
50 respondents scored 7 or 8 (passives)
30 respondents scored 0-6 (detractors)

Step 1 — calculate percentages:

% Promoters = 120 / 200 × 100 = 60%
% Passives = 50 / 200 × 100 = 25%
% Detractors = 30 / 200 × 100 = 15%

Step 2 — apply the formula:

NPS = 60% − 15% = +45

+45 is an excellent score. Compare it against industry benchmarks below to know whether it is competitive in your sector.

How to calculate NPS from a list of individual scores

If you have a CSV or spreadsheet column of raw scores rather than aggregated counts, the process is the same but you need to classify each row first. The fastest way is to paste the column into the free NPS calculator — switch to "By Scores" mode and the classification runs automatically.

If you prefer to do it manually in a spreadsheet, use the following formula in a helper column on the 0-10 scale:

=IF(A2>=9,"Promoter",IF(A2>=7,"Passive","Detractor"))

Then use COUNTIF to tally each category and apply the NPS formula by hand.

How many responses do you need?

NPS is a statistical measure and is sensitive to small samples. As a rule of thumb:

Under 100 responses: directional only — useful for trend-watching, not for executive reporting
100-400 responses: the score is reliable to ±5 points
400+ responses: the score is reliable to ±3 points and is safe to segment by location or channel

Aim for a response rate above 20% from your survey audience. Lower response rates risk self-selection bias — usually it is the most-satisfied and most-dissatisfied customers who answer, while the silent majority of passives is under-represented.

What is a good NPS score?

The headline rule: any positive NPS means you have more promoters than detractors. But the absolute number must be compared against your industry, not against a universal target.

Above +70 — world-class. Rare even among loved consumer brands.
+50 to +70 — excellent.
+30 to +50 — good. The bulk of healthy organisations sit here.
0 to +30 — adequate. There is real room to improve customer experience.
Below 0 — critical. More customers actively damage your reputation than promote it.

Average NPS by sector (broad ranges):

Hospitality and education: +35 to +55
Retail: +30 to +45
Financial services: +25 to +40
Airlines: +20 to +35
Municipal services: +15 to +30
Public transport: +10 to +25

A +25 in public transport is roughly equivalent to a +50 in hospitality. Benchmark against your own sector.

Common mistakes when calculating NPS

Mistake 1 — including passives in the formula

The formula is % Promoters − % Detractors. Passives appear in the denominator (they are part of the total) but they do not get added or subtracted. A spreadsheet that subtracts (% Detractors + % Passives) from % Promoters will produce a number that looks like NPS but is mechanically wrong.

Mistake 2 — mixing scales

A 1-100 score of 90 is roughly equivalent to a 0-10 score of 9. But the cutoffs are not linear — 70 on a 1-100 scale is a passive, while 7 on a 0-10 scale is the lower end of passive. Pick one scale per survey and stay consistent.

Mistake 3 — running the calculation on too small a sample

An NPS calculated from 20 responses can swing 20 points just from one or two people changing their minds. Always report the sample size alongside the score, and treat small-sample NPS as directional only.

Mistake 4 — reporting NPS without trend data

A single NPS number is far less useful than the trend over time. Always plot NPS month-on-month or quarter-on-quarter — the direction matters more than the absolute value.

Use the free NPS calculator

The fastest way to compute your NPS is to use the free NPS calculator. Two modes:

By Count — enter the number of promoters, passives, and detractors. Useful when you already have classified totals.
By Scores — paste a raw list of 1-100 scores separated by commas. The calculator classifies each one, applies the formula, and shows the result with an interpretation, breakdown, and gauge.

The math runs entirely in your browser — no data leaves your device, no signup, no upsell.

From spreadsheet NPS to automated NPS

Calculating NPS manually works for a single survey at a single point in time. It does not scale to:

Continuous measurement across many channels (QR, email, web)
Segmentation by location, staff member, or service type
Real-time alerts when scores drop below a threshold
Long-running trend analysis with regression and seasonality

That is where a dedicated feedback platform like kazva.bg takes over. The math is the same — the value is in collecting honest responses continuously and turning them into actionable signals for the business. See how kazva.bg works for the operational picture.

How to Calculate NPS — Step-by-Step Guide to the Net Promoter Score Formula