How many participants do I need for qualitative research? A better way to decide
How many participants do you need for qualitative research?
It’s one of the most common questions asked by PhD researchers. It often feels as though there must be a hidden answer somewhere. Other researchers know, but are not sharing, it feels like you’re the only person who isn’t in on the secret.
To explain why the real answer is more complicated than that, I want to begin with a story.
Back in 2019, I signed up for a local half marathon and rediscovered how much I loved running.
I took the training seriously. Soon, I was online trying to work out exactly what I should be doing. How many miles should I run each week? How many strength sessions? Which exercises? How many sets and repetitions? What weight should I be lifting?
There was no shortage of advice.
The problem was that much of it conflicted. One source insisted long slow miles were everything. Another prioritised speed work. Some recommended heavy lifting. Others warned against it. Plenty of people offered numbers, plans, and rules. Far fewer explained the reasoning behind them.
That mattered.
Because the right answer would depend on things such as my age, fitness level, injury history, available time, and goals for the race. Training for a first half marathon is different from chasing a personal best. Preparing at 25 is different from preparing at 38. Context changes everything.
Trying to decide how many participants you need for a qualitative study is often rather similar.
Many researchers search for a number when what they really need is a framework for making the decision.
Why there is no single magic number in qualitative research - think range and rationale
In very general terms, here is what I would advise in terms of ranges of numbers acceptable in particular approaches:
Narrative Inquiry: 1-4 participants
Phenomenology: 4-10 participants
Grounded Theory: 20-30 participants
Ethnography: 30-50 participants
Reflexive Thematic Analysis: 10-20 participants
But - please ensure there is a clear rationale behind your numbers, because numbers detached from context can be misleading.
In the twenty years I’ve spent supporting qualitative researchers, one of the most common sources of confusion is treating sample size as a technical box to tick rather than a methodological decision.
The better starting point is not:
How many participants do I need?
It is:
What kind of understanding am I trying to produce, and how deeply do I need to understand it?
That question changes everything.
Most well-designed qualitative studies are not judged on whether they had a perfect sample size. Speaking as an experienced PhD examiner, I’ve never penalised someone on sample size alone. I have however grilled people on why that same size was appropriate for their research. I was not looking for a magic number, I was looking for a rationale.
A justified decision is usually stronger than a borrowed number.
What determines qualitative sample size?
Several factors shape how many participants may be appropriate.
(1) Your research aims
Are you trying to develop rich, detailed understanding of lived experience?
Or are you looking for broader patterns across a wider group?
A study exploring the experiences of first-generation university mathematics students may need fewer participants than a project comparing experiences across multiple institutions and demographic groups.
Depth and breadth often pull in different directions.
(2) Your methodology
Different qualitative approaches usually involve different sample sizes.
For example:
Interpretative Phenomenological Analysis (IPA) often needs smaller samples because the focus is detailed idiographic understanding.
Reflexive Thematic Analysis can work with smaller or larger datasets depending on the research question and analytic depth.
Grounded Theory may involve iterative sampling as concepts develop.
Case Study Research may focus deeply on one case or a small number of cases.
Methodology matters because it shapes what counts as meaningful knowledge.
(3) Depth of data collection
Ten brief 20-minute interviews are different from ten interviews lasting two hours each with follow-up conversations.
Likewise, a project using diaries, observations, and repeat interviews may generate substantial depth from a modest number of participants.
It is not simply about participant count. It is also about data richness.
(4) Diversity and complexity
If your study includes participants across different professions, age groups, organisations, or countries, you may need more participants to meaningfully explore variation.
If the group is narrower and more specific, fewer may be appropriate.
Why searching for the “right number” can keep you stuck
Many PhD researchers become anxious here because they want certainty before moving forward - that is understandable.
Numbers feel concrete, they look defensible and seem easier to justify than judgement.
Yet qualitative research often asks something more demanding of you: thoughtful reasoning.
This can feel uncomfortable, especially early in the PhD, because it requires you to tolerate a degree of uncertainty while making decisions you can later explain.
A more useful way to decide participant numbers
Instead of asking only how many, ask yourself:
What am I trying to understand?
How much depth does this question require?
What methodology am I using, and what does it usually prioritise?
How rich will each data source be?
How much variation matters in this study?
What is realistic within my time, access, and resources?
Those questions will usually take you much further than searching for a magic number.
What about saturation?
Many researchers encounter the word saturation and assume this solves everything.
In practice, saturation is more complicated than it is often presented, and it does not fit every qualitative methodology equally well.
For some approaches, particularly reflexive thematic analysis, many scholars would argue that depth, meaning, and interpretive richness are more helpful guiding ideas than chasing a simplistic notion of saturation.
This is another reason why context matters.
When I was training for that half marathon, I eventually stopped searching for universal answers and started asking better questions about my own context, goals, and needs.
That is what helped.
Qualitative sample size decisions tend to work in much the same way. You are rarely looking for a secret number. You are looking for a reasoned, defensible decision that fits the kind of understanding your study is trying to produce.
If you’d like structured support with methodology decisions
If questions like sample size, paradigms, methods, data collection, or analysis are currently making your PhD feel harder than it needs to, my Methodology, Data Collection & Analysis PhD Survival Guide was created for exactly this stage.
It offers grounded, structured support for making methodological decisions with more confidence and clarity.
It’s there when you need it.
From “I’m not sure this makes sense” to a clear, defensible research design.
If your qualitative methodology, data collection, or analysis feels unclear, disconnected, or harder than it should, this guide will help you make sense of your decisions and explain them with confidence.
Many capable researchers reach the point where things stop feeling straightforward.
You may have data, but feel unsure what to do with it.
You may be writing your methodology chapter, but not know how to explain or justify your choices.
You may sense that parts of the project no longer fit together as clearly as they should.
That usually means you have reached the stage where qualitative research asks for coherence, judgement, and clarity - this guide is designed to help you through that stage.
Inside, I show you how to bring your research questions, methods, data collection, and analysis into a coherent whole, so that your project makes sense to you and can be clearly communicated to others.
You’ll learn how to:
align your research questions, methods, and data
understand what you are doing when you analyse qualitative material
make decisions you can justify with confidence
approach your methodology chapter with more clarity and structure
move forward without constantly doubting yourself
Whether you are refining your design, collecting data, analysing interviews or documents, or trying to write everything up clearly, this guide meets you where you are.
Across 12 carefully sequenced sections and practical worksheets, it helps you move from uncertainty and overthinking to clarity, coherence, and steady progress.
This is a digital download, so you’ll receive immediate access after purchase and can begin straight away.
Swipe through the images above to see what’s inside.
If you’d like one complete system for your qualitative PhD, you can also access all four PhD Survival Guides here.
If you have any questions, feel free to contact me. I’ll be happy to help.
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