How to Calculate NPS: Formula, Example and Pitfalls

To calculate NPS (Net Promoter Score), ask customers "How likely are you to recommend us to a friend or colleague?" on a 0 to 10 scale, then subtract the percentage of detractors (scores 0–6) from the percentage of promoters (scores 9–10): NPS = % promoters − % detractors. Passives (7–8) count toward the total but are not subtracted or added. For example, 120 promoters, 55 passives and 25 detractors out of 200 responses give 60% − 12.5% = +47.5, usually reported as +48.

This guide walks through the formula, a worked example, the margin of error that comes with small samples, how to segment results and how to act on them. You can check every number here with the free NPS calculator.

Step 1: Ask the question the standard way

On a scale from 0 to 10, how likely are you to recommend [company] to a friend or colleague?

Label the ends: 0 = "Not at all likely", 10 = "Extremely likely". Keep the wording stable over time. If you change it, earlier and later scores are no longer comparable.

Add one optional open question:

What is the main reason for your score?

That second question is where most of the insight comes from.

Step 2: Group the responses

Score	Group	What it usually indicates
9–10	Promoters	Enthusiastic; likely to recommend and stay
7–8	Passives	Satisfied but not enthusiastic; open to alternatives
0–6	Detractors	Unhappy or indifferent; may leave or speak negatively

Step 3: Apply the formula

NPS = (promoters ÷ total responses × 100) − (detractors ÷ total responses × 100)

Worked example

You receive 200 responses:

Group	Count	Share
Promoters	120	120 ÷ 200 = 60.0%
Passives	55	55 ÷ 200 = 27.5%
Detractors	25	25 ÷ 200 = 12.5%

NPS = 60.0 − 12.5 = +47.5

Because NPS is the difference between two percentages, it is reported as a number (+47.5 or rounded to +48), not as "47.5%".

From raw scores

If you have a spreadsheet column of individual scores, count how many are 9 or 10, and how many are 6 or below. In most spreadsheet tools:

• Promoters: count of values greater than or equal to 9
• Detractors: count of values less than or equal to 6
• Total: count of all values

Or paste the column into the NPS calculator, which also shows the full score distribution.

Step 4: Check the margin of error

NPS from a survey is an estimate. With few responses, random variation can be large. The standard approximation for the 95% margin of error is:

Margin of error ≈ 1.96 × √( (p + d − (p − d)²) ÷ n ) × 100

where p is the promoter share, d the detractor share (both as decimals) and n the number of responses.

For the example above (p = 0.60, d = 0.125, n = 200):

• p + d = 0.725
• (p − d)² = 0.475² ≈ 0.2256
• Variance term: 0.725 − 0.2256 = 0.4994
• 0.4994 ÷ 200 = 0.002497; square root ≈ 0.0500
• 1.96 × 0.0500 × 100 ≈ ±9.8 points

So the "true" NPS for this customer base is likely somewhere between about +38 and +57. How the margin shrinks with more responses (same shares as above):

Responses	Margin of error (approx.)
50	±19.6
100	±13.9
200	±9.8
500	±6.2
1,000	±4.4

Practical consequence: if your NPS moves from +42 to +47 with 100 responses each time, that change is well within the noise. Look for consistent trends over several surveys, not single movements.

Step 5: Segment the results

A single NPS for all customers hides differences. Break it down where you have enough responses:

• By customer type or size
• By product or service line
• By how long they have been a customer
• By region or location
• By the last interaction they had (support contact, delivery, project)

Example. Overall NPS is +30. Split by tenure:

Tenure	Responses	NPS
Under 6 months	80	+10
6–24 months	120	+35
Over 2 years	100	+40

The low score among newer customers suggests the early experience needs work, which an overall figure would not reveal. A customer onboarding checklist is the obvious next step in this case. Keep the margin of error in mind: with 80 responses, the segment's NPS could easily be ten or more points off.

Step 6: Close the loop

Closing the loop means following up with respondents, especially detractors. It turns the survey from a measurement into a retention tool.

Follow-up by group

Group	Follow-up	When
Detractors	Personal contact: thank them, understand the issue, fix what you can	Within 2–3 working days
Passives	Ask what would make the experience better; act on common themes	Within 1–2 weeks, or in a batch
Promoters	Thank them; where appropriate, ask for a review or referral	Within 1–2 weeks

Detractor follow-up template

Hi [first name], thank you for answering our survey. I saw that your experience hasn't been what it should be, and I'd like to understand what happened. Would you have ten minutes for a call this week, or would you prefer to reply here?

Then listen, record the reason in your CRM and fix what you can. Our guide on how to handle customer complaints covers the conversation itself.

Analysing the open answers

Read every comment and tag it with one or two themes (for example "delivery speed", "price", "staff friendliness", "product quality"). Count the themes by group. The most frequent detractor themes are your priority list; the most frequent promoter themes are what to protect and talk about in your marketing.

When to send an NPS survey

• Relationship NPS: to all active customers, a few times a year. Good for tracking the trend.
• Transactional NPS: after a milestone such as a completed project or the end of onboarding. Useful, but be careful: for individual interactions, CSAT or CES is often the better measure (see NPS vs CSAT vs CES).

Do not send NPS right after a support ticket if you are also asking for CSAT; customers should not get two surveys for the same moment.

Common mistakes

• Reporting NPS as a percentage. It is a score from −100 to +100.
• Comparing with numbers from other companies. Industries, customer groups and survey methods differ too much. Compare with yourself over time.
• Asking for a 10. "Please rate us 10!" makes the result meaningless.
• Surveying only happy customers. Sending surveys only after successful interactions inflates your score.
• Ignoring passives. They are often the easiest group to move, and the group most likely to leave quietly for a competitor.
• Not acting. Customers who give feedback and see nothing happen stop responding.

Your next step

Collect your latest NPS responses, paste them into the NPS calculator, and note both the score and the margin of error. Then read the comments from detractors and tag them by theme. Pick the most common theme and assign an owner to fix it before your next survey. For more question ideas to add alongside NPS, see our list of customer feedback survey questions.