The KJ Method: Affinity Diagrams That Tame 50+ Ideas

Hey everyone ☕

Ever stared at a Miro board or a whiteboard after a workshop and thought…

“Okay, we have hundreds of ideas. Now what?”

Those moments after a workshop when the wall looks like modern art... full of ideas, notes, and zero clarity?

Yeah, that kind 🫣

“So… what do we actually do with all this?” 💭

Here’s a tool that turns that chaos into clarity. Fast! 🚀

Imagine taking 50+ raw notes from interviews, brainstorms, or feedback threads and watching them shape themselves into 5-7 clear themes... all in one session.

That’s the magic of the K‑J Method (also known as the Affinity Diagram).

Developed by Japanese anthropologist Jiro Kawakita, it’s one of those timeless techniques that keep teams aligned and decisions grounded.

It’s not fancy, but it works.

What is the KJ Method (and why is it called an affinity diagram)?

The KJ Method, named after Japanese anthropologist Jiro Kawakita, is a bottom-up technique for organizing a large set of ideas or data into logical groups. You cluster items by similarity first and name the themes only after they emerge, which is why it is also called an affinity diagram: items group by their natural affinity.

Originally developed in the 1960’s, this method helps groups organise a large set of ideas or data into logical groups. 

It’s completely bottom-up: you don’t impose themes. The themes emerge. 

When should you use an affinity diagram (and when shouldn't you)?

Use it after ideation or research, whenever a group is staring at dozens of notes with no clear next step. Skip it when you have fewer than about 20 items or the themes are already obvious: below that, clustering adds ceremony without insight. The method really shines from 40-50 items upward.

• Post-ideation: you’ve run a brainstorming session or user research and you have dozens of cards or notes. 
• When you need team alignment, everyone contributes to the grouping, which builds shared understanding. 
• You’re facing high ambiguity or complex data sets: many voices, many ideas, no clear next step.
• Retrospectives! Same thing... You got the picture.

How do you run an affinity mapping session, step by step?

Here’s how I usually guide a team/company through it:

1. Gather and record
   Ask participants to capture ideas or data points that come from research, feedback, one per sticky or virtual note. No discussion yet. 
2. Silent grouping
   Without a large discussion, the group (or individuals) cluster notes by similarity. No labels yet. Let patterns emerge. 
3. Label/name clusters
   Once grouping is complete, assign a label that captures the theme for each group, like Onboarding friction, Integration gaps, or Data visibility.
4. Discuss, then act
   Review the clusters together. What surprised you? What themes connect?Choose 2-3 (or 3-5) clusters to focus on next, the ones that move the needle.

The result?

Instead of staring at a wall of noise, you walk away with a few clear themes, a narrative you can share with your team, investors, or stakeholders.

It’s clarity you can act on, not just talk about.

Why does this method still matter?

In today’s world:

• Remote/hybrid teams generate lots of ideas (Slack threads, Miro boards, survey feedback, Notion comments, etc.).
• Stakeholders from many functions demand clarity.
• The tool you use has to build shared meaning, not “my idea vs your idea”.

The K-J Method offers:

• Inclusivity: Everyone contributes to clustering.
• Clarity: You convert unstructured input into a visual map of themes.
• Actionability: The clusters become talking points for next steps, not just more ideas.

Affinity diagram vs mind map vs card sorting: which one do you need?

These three get lumped together, and they solve different problems. An affinity diagram is bottom-up: themes emerge from clustering unstructured items. A mind map is top-down: you start from a central concept and branch outward, one brain exploring one idea. Card sorting tests how users group predefined items, usually to design navigation or information architecture.

The quick rule: use affinity mapping to find themes in messy input, a mind map to explore a single idea, and card sorting to validate a structure with real users.

Is affinity mapping rigorous enough, or do you need thematic analysis?

For most product decisions, affinity mapping is enough: it is fast, collaborative, and produces themes the team believes in because they built them together. Thematic analysis is its slower, more systematic cousin, with coded data and documented criteria. Reach for it when the research will be scrutinized, published, or used to justify a major bet. For everything else, cluster and move.

Practical tips

• Use a physical board (if co-located) or virtual board (Miro, Mural), depending on team setup.
• Avoid early labelling: Let items cluster freely before naming groups. 
• Time-box the silent grouping stage: e.g., 15-20 minutes keeps energy up.
• Capture the board: take a photo or export the virtual board. It becomes your artefact for stakeholder alignment.
• In mentoring: Use this method to help mentees organise their learning goals, feedback items, or portfolio ideas.
• Revisit the clusters regularly (on a cadence the team agrees on).
  Check: Did the themes hold up? Did they drive action? Reflection keeps them relevant.

Key takeaway

The K-J Method (Affinity Diagram) isn’t flashy, but it works.

When you have many ideas and low clarity, this method gives you structure, alignment and action.

Next time your board is full of unmapped sticky-notes, skip another brainstorming session. Start clustering instead.

And once the clusters exist, two natural next steps: Jobs to Be Done tells you which cluster actually matters to users, and if the notes came from user interviews, my UserInterviewKit handles the synthesis step for you.

Let’s Connect

If this sparked ideas for your product, or made you realize your team could use more clarity after those “post-it storms”, let’s connect.

I can help you turn this method into something your team actually uses, simple, structured, and repeatable.

I help teams bridge UX, business models, and product psychology, turning scattered insights into strategy that scales.

→ Book a call

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See ya!