Net Promoter Score (NPS): How to Measure Customer Loyalty
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Net Promoter Score is a simple way to find out how likely your customers are to recommend you. It boils down to one question and one number, which makes it easy for a small business to start using right away.
This guide explains what NPS is, how to calculate it, walks through an illustrative example for a local auto repair shop, and covers the mistakes that make the score misleading.
What Is Net Promoter Score?
Net Promoter Score (NPS) measures customer loyalty by asking one question:
“On a scale of 0 to 10, how likely are you to recommend us to a friend or colleague?”
Answers are sorted into three groups:
- Promoters (9 or 10): happy, loyal customers who are likely to recommend you.
- Passives (7 or 8): satisfied but not excited. They could switch to a competitor easily.
- Detractors (0 to 6): unhappy customers who may warn others away.
NPS was introduced by Fred Reichheld of the consulting firm Bain & Company in a 2003 Harvard Business Review article, “The One Number You Need to Grow.”
For a small business, it’s useful because word of mouth is often the cheapest way to win new customers. More promoters usually means a lower customer acquisition cost.
The NPS Formula
NPS = % of promoters − % of detractors
Passives count toward the total number of responses, but aren’t added or subtracted.
The score ranges from −100 (everyone is a detractor) to +100 (everyone is a promoter). It’s written as a plain number, not a percentage.
Worked Example: A Local Auto Repair Shop
An auto repair shop texts a one-question survey to customers a day after each repair. Over a month, 80 customers reply. All figures are illustrative.
| Group | Scores | Responses | Share |
|---|---|---|---|
| Promoters | 9–10 | 44 | 55% |
| Passives | 7–8 | 24 | 30% |
| Detractors | 0–6 | 12 | 15% |
| Total | 80 | 100% |
NPS = 55 − 15 = +40
The number is only half the value. The shop also asks a follow-up: “What’s the main reason for your score?” Reading the 12 detractor comments, the owner finds that 7 mention the same thing: repairs running past the promised pickup time.
That’s a fixable problem. The shop starts texting customers the moment a job is delayed, with a new pickup time. Three months later, the detractor share drops to 8% and the promoter share rises to 60%, giving a new NPS of +52.
What Is a Good NPS?
There’s no single “good” score. It varies a lot by industry and by how you survey. As a rough guide:
- Above 0: more promoters than detractors.
- Above +30: generally a healthy score.
- Above +50: strong loyalty.
The most useful comparison is your own score over time. If it’s rising, you’re heading the right way.
Also keep the method the same each time. A survey sent right after a repair will usually score differently from one sent a month later, so changing when or how you ask can move the number even if nothing in the business changed.
How to Run NPS in a Small Business
- Ask at the right moment. Send the survey soon after the purchase or service, while it’s fresh.
- Keep it short. The 0 to 10 question plus one open “why” question is enough.
- Ask everyone, not just happy customers. Picking who you survey makes the score meaningless.
- Close the loop. Reach out to detractors to fix the problem, and invite promoters to leave a review or refer a friend.
- Track it monthly or quarterly. Look for trends and patterns in the comments.
Promoters tend to come back more often and spend more over time, which raises customer lifetime value. Fewer detractors also means a lower churn rate.
Common Mistakes With NPS
- Chasing the number instead of the feedback. The comments tell you what to fix. The score just tells you whether it’s working.
- Asking for a high score. “Please give us a 10!” ruins the data. Let customers answer honestly.
- Surveying too few people. With 10 responses, one grumpy customer swings the score a lot. Wait for a reasonable number before drawing conclusions.
- Comparing with very different businesses. An auto shop and a software company score very differently. Compare with yourself first.
- Never following up with detractors. An unhappy customer who gets a call and a fix often becomes a loyal one.
Frequently Asked Questions
Can NPS be negative?
Yes. If you have more detractors than promoters, the score is below zero. It’s a signal to read the feedback closely and fix the main complaints.
Why are scores of 7 and 8 not counted?
Passives are counted in the total responses but not added or subtracted. They’re satisfied but not enthusiastic, so they’re unlikely to recommend you or warn others away.
How many responses do I need for a reliable NPS?
More is better. With very few responses, a single answer can move the score a lot. Many small businesses wait for at least a few dozen before comparing periods.
How often should I measure NPS?
Many businesses survey after each purchase and review the score monthly or quarterly. That’s often enough to spot trends without bothering customers.
Is NPS the same as customer satisfaction?
Not quite. Satisfaction surveys ask how happy someone was with one experience. NPS asks whether they’d recommend you, which is a stronger sign of loyalty.
