How to Calculate NPS: The Formula, With a Worked Example

TL;DR

• The NPS formula is simple: percentage of Promoters minus percentage of Detractors.
• Promoters score 9 to 10, Passives 7 to 8, Detractors 0 to 6. Passives count toward your total responses but drop out of the subtraction.
• The result is a number from -100 to +100, not a percentage. The math takes a minute. Measuring at the right moment, and acting on it, is the part that matters.

Calculating NPS is one of the easiest things in customer experience measurement. It is one question, two percentages, and a subtraction. The mistakes people make are almost never in the arithmetic. They are in how the number is read and how rarely it is acted on.

The NPS formula

NPS = % Promoters minus % Detractors

That is the whole formula. You survey customers with the standard question, sort the answers into three groups, work out what share of all responses are Promoters and what share are Detractors, and subtract the second from the first.

Step 1: Ask the question and sort the responses

Every NPS starts with the same question, scored 0 to 10: "How likely are you to recommend us to a friend or colleague?" Sort the answers into three groups:

Passives are the trap most people miss: they are included in the denominator (your total responses) but not in either percentage you subtract.

Step 2: Work out the percentages and subtract

Turn each group into a percentage of your total responses, then subtract.

How to calculate NPS: a worked example

This is how NPS is calculated by hand. An NPS calculator does the same subtraction for you, but it helps to see the steps once. Say you survey 200 customers and get:

• 120 Promoters
• 40 Passives
• 40 Detractors

Promoters are 120 of 200, which is 60 percent. Detractors are 40 of 200, which is 20 percent. Passives (the other 20 percent) are set aside.

NPS = 60 minus 20 = 40.

Your Net Promoter Score is 40. Note that it is written as 40, not 40 percent, because it is a number on a -100 to +100 scale, not a proportion. That distinction trips up more teams than the math does, and it is worth reading why NPS is not a percentage.

Common mistakes when calculating NPS

• Reading it as a percentage. NPS is a number from -100 to +100. Calling it "40 percent" is wrong and misleads everyone downstream.
• Dropping Passives from the denominator. They do not count toward either percentage, but they do count toward the total. Leave them out of the base and your score inflates.
• Too small a sample. A score built on a handful of responses swings wildly. You need enough responses for the number to be stable before you act on it.
• Averaging the 0 to 10 scores. NPS is not the average rating. It is the Promoter percentage minus the Detractor percentage. They are different numbers.

When and how often to measure

An NPS you measure once a year is a post-mortem. By the time the number moves, the customers who moved it are already gone.

There are two moments to measure, and they answer different questions. Relationship NPS asks periodically about the overall relationship. Transactional NPS asks right after a specific interaction, like a support call or a delivery, and it is far more actionable because it points at a moment you can fix. Most strong programs run both, and the difference between them is worth understanding before you design your survey: see transactional versus relationship NPS.

Frequency is where the metric lives or dies. As of 2026, an annual score is a history lesson. Measuring close to the experience, continuously, is what lets you catch a Detractor while they are still your customer.

Turn the calculation into action

An annual NPS tells you who already left. Measure it at the moment of the experience, while you can still do something about it.

Amitayu Basu, CEO, Numr

The formula introduced by Fred Reichheld in the 2003 Harvard Business Review article "The One Number You Need to Grow" was never meant to end at a number. The point of calculating NPS is to know which customers to act on. A Detractor identified today and contacted today can be saved. The same Detractor found in next quarter's report has usually already churned. Turning the score into a routed, closed loop is covered in closing the loop on feedback, and it is what separates measuring NPS from using it. For the metric itself and its benchmarks, see what NPS is and what counts as a good score.

Frequently asked questions

How do you calculate NPS? Subtract the percentage of Detractors (scores 0 to 6) from the percentage of Promoters (scores 9 to 10). Passives (7 to 8) count toward your total responses but not toward either percentage.

What is the NPS formula? NPS = percentage of Promoters minus percentage of Detractors. The result runs from -100 to +100.

Can you show an NPS example? With 120 Promoters, 40 Passives, and 40 Detractors out of 200 responses: Promoters are 60 percent, Detractors are 20 percent, so NPS = 60 minus 20 = 40.

Is NPS an average of the scores? No. NPS is not the average 0 to 10 rating. It is the Promoter percentage minus the Detractor percentage, which is a different calculation.

How often should you measure NPS? As close to the experience as possible. Transactional NPS after key interactions is more actionable than a once-a-year relationship survey, and most strong programs run both.

Net Promoter Score, Net Promoter, and NPS are registered trademarks of Bain and Company, Satmetrix Systems, and Fred Reichheld.