In the world of product design and innovation, user interviews are a bit like gold dust. Get them right, and you can uncover the kind of insights that spark breakthrough ideas. Get them wrong (or overdo them), and you’re left swimming in data with no real direction.

So, how many interviews do you actually need to get those all-important lightbulb moments?

The Importance of User Interviews

User interviews are a cornerstone of any good research process. Unlike analytics dashboards or survey data, interviews give you the context, emotion, and nuance behind user behaviour. They help you understand not just what users are doing, but why they’re doing it.

Whether you’re a UX designer, a service designer, a product owner or a marketer, user interviews are a vital tool for making strategic decisions grounded in real human experiences.

Why Quality Over Quantity Wins Every Time

There’s a common assumption that more interviews = better data. But when it comes to qualitative research, that’s not necessarily true. In fact, a handful of well-conducted interviews will often tell you far more than a dozen rushed ones.

Let’s say you’re launching a new children’s toy. Interviewing five parents and children deeply and thoughtfully will likely surface the core motivations, frustrations, and priorities. Interviewing 20 in a superficial way might leave you with vague generalisations and little to act on.

The Magic Number: Five

That’s right. Just five.

According to the Nielsen Norman Group; five user interviews can uncover up to 80% of the major insights. After that, you start hitting the law of diminishing returns. Each new interview adds less and less to your understanding.

Of course, five isn’t gospel. You may need more depending on the complexity of your product or the diversity of your audience. But as a starting point? Five is solid.

When You Might Need More Than Five

If you’re working on a product that has multiple user types, or one that solves a particularly complex problem, you’ll want to expand your pool. For instance, developing an educational toy? You’ll want feedback from parents, teachers, and children across different age groups.

In those cases, think in groups of five. Five per user segment is a smart rule of thumb.

Key Factors That Influence Your Sample Size

Here are a few things to consider when deciding how many interviews you need:

• Product Complexity: The more complex the product, the more interviews may be needed to unpack all the angles.

• User Diversity: A wide range of user backgrounds? You’ll need a wider pool.

• Stage of Development: Early-stage projects may benefit from broader input, while late-stage work might just need a few final validation interviews.

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Tips for Getting the Most from Every Interview

Whether you’re speaking to five people or fifteen, how you conduct the interview is what makes the difference.

• Set clear goals: Know what you want to learn before you begin.

• Ask open-ended questions: Avoid yes/no responses. Go for hows and whys.

• Create a comfortable setting: People open up more when they feel relaxed.

• Record and review: Always get consent, but having a recording allows you to fully focus on the conversation and catch subtleties you might miss in real time.

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Turning Insights into Action

Once you’ve completed your interviews, the next step is analysis. Look for themes, patterns, and repeated pain points. These are your gold nuggets. Use them to:

• Guide product decisions

• Improve user experience

• Shape strategic direction

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Final Thoughts

In research, as in life, it’s not how many people you talk to; it’s how well you listen. Five thoughtful, well-prepared interviews can tell you almost everything you need to know.

So next time you’re gearing up for a round of interviews, remember keep it focused, keep it human, and keep your ears wide open.

Curious about user research frameworks that can help you design better interviews and decode feedback like a pro?

Have a look at our practical courses; designed to help you master user research, consumer psychology, and behaviour design.

Let’s make those interviews count.