The Feynman technique: explain it simply to find out if you get it

The Feynman technique is a way of studying where you explain a topic as if to someone who knows nothing about it, in plain words and without your notes, to find the exact spot where your explanation falls apart. Wherever you stall, or have to hide behind a technical term, is what you don't understand yet. You go back to the material, fix it and explain it again.

It comes down to four steps: pick a concept, explain it simply, find the gaps and go back to the source, then simplify until it makes sense on its own. It works because it forces you to pull the topic out of memory and put it in order, which is exactly what the exam will ask of you.

I'm in my final year of computer engineering, and I use it mostly on topics I think I already know, because those are the risky ones. To show how it works I picked an example from a different field, intro macroeconomics, because it's a great case of an explanation that sounds complete and has a hole in the middle.

Where the name comes from

Richard Feynman was an American physicist who won the Nobel Prize in Physics in 1965 and was famous for explaining hard ideas with everyday examples, in his lectures and in his popular books. He never wrote down a four-step method with his name on it. The "Feynman technique" is a later way of summing up how he studied and taught, built around one distinction he kept coming back to: knowing the name of something is not the same as understanding how it works.

That distinction is the whole point. You can know that photosynthesis "converts light energy into chemical energy" and have no idea what actually happens in the leaf. The technique helps you notice the difference before your professor does.

The four steps

1. Pick one concept and write it at the top of a page

One, and a specific one. "Inflation" works; "macroeconomics" doesn't. If the topic is big, break it up: first what inflation is, then how it's measured, then what causes it.

2. Explain it to someone who knows nothing about it

Without looking at your notes, write or say out loud an explanation for someone outside your major: a younger sibling, a roommate in another program, your grandmother. Short sentences, everyday words and one example. If a technical term shows up, you have to be able to explain that too.

3. Mark where you got stuck and go back to the material

Read what you wrote and mark three things: where you didn't know how to continue, where you used jargon to cover a gap, and where you jumped from one idea to the next without connecting them. Only then go back to the slide or the textbook, and only to that part, not the whole chapter.

4. Simplify and explain it again

Rewrite the explanation with your fixes, shorter and with a better example. If there's still a jump, repeat step three. You're done when you can explain it straight through without notes and without leaning on any difficult word.

An example with inflation

Say your Econ 101 lecture had a slide that read "inflation: a sustained, general increase in the price level." First attempt, no notes:

"Inflation is when stuff gets more expensive. The same dollar buys you less than before. It happens because there's more money."

Sounds fine. Look closer and three gaps show up:

• "Stuff gets more expensive" is vague. If only the price of eggs goes up, is that inflation? No. The slide said "general" and "sustained." One price jumping once doesn't count.
• "There's more money" is jargon dressed up as plain English. More money compared to what? If the economy produces more goods at the same pace, prices don't have to move. You need "more money relative to what's being produced."
• You skipped the other causes. The lecture also covered rising costs (like energy) and the fact that if everyone expects prices to rise, they do. Your version had only one.

Second attempt: "Inflation is when almost all prices go up and keep going up for a while, so the same amount of money buys less and less. It can happen because there's more money around than things to buy, because making things gets more expensive, or because people expect prices to rise and act ahead of it."

The second version isn't longer because of padding. It's longer because it now says what the first one was hiding.

Why it works

The Feynman technique isn't magic or a memory hack. It bundles a few things we know work when you study:

• It's active recall. Explaining without notes forces you to retrieve the topic from memory, which makes it stick far better than rereading. I go deeper into that in the post on active recall.
• It exposes the illusion of knowing. When you reread, everything feels familiar and you think you get it. When you explain, the gaps show up on their own. It's the same trap I describe in does rereading work.
• It forces connections. To explain something to another person, loose facts aren't enough: you have to say why one leads to the next. That's the line between understanding and memorizing.

Using it with your lecture slides

It pays off most with your professor's slides, which usually give you the name of things and very little of the explanation. One concrete routine:

1. Look only at the slide title and cover the rest.
2. Explain out loud what the slide should say, as if to a classmate who missed the lecture.
3. Uncover it and compare. Anything extra you said is fine; anything you missed is what you review.

You can do it alone by recording yourself on your phone, or in pairs: one person explains and the other is only allowed to interrupt with "wait, what does that mean?" In courses with oral exams or presentations, it's basically a rehearsal.

In Filmina, the web app I built to study from your own lecture slides, this idea lives inside Practice: some questions ask you to explain the concept in your own words, typed or dictated, and others ask you to explain it to a classmate who missed class. Your answer is compared against the concept that was asked, and it tells you which ideas you covered and which you missed, which is step three of the technique.

The most common mistakes

• Picking a topic that's too big. "Explain the French Revolution" isn't a concept, it's a semester. Pick one cause, one process, one definition.
• Looking at the material while you explain. If you're reading, you're repeating, not explaining. No notes first; compare after.
• Simplifying until it's wrong. Simple isn't sloppy. "Inflation means things are expensive" is simple and incorrect. The goal is to say what the slide says in everyday words, not to say less.
• Doing it only in your head. Thinking "yeah, I could explain this" doesn't count. Write it or say it out loud, because that's where the jumps show up.
• Using it for everything. For memorizing a list of dates or bones, flashcards do better. The Feynman technique is for what you need to understand.

Frequently asked questions

What is the Feynman technique for studying?

It's a method where you explain a topic in simple words, as if to someone with no background, to find the parts you don't actually understand. Wherever you get stuck, you go back to the material, fix it and explain it again until it flows.

What are the 4 steps of the Feynman technique?

Pick a specific concept, explain it simply without your notes, mark the gaps and go back to the source only for those parts, then simplify the explanation until it works without any jargon.

Does the Feynman technique work for every subject?

It works for anything you need to understand: processes, mechanisms, theories, proofs or concepts in any major. For material you mostly have to memorize, like names or dates, flashcards and spaced repetition work better.

Can you do the Feynman technique alone?

Yes. Write the explanation on paper or say it out loud while recording yourself, then compare it with the material. A study partner helps because they interrupt where it stops making sense, but you don't need one.