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How to revise with flashcards.
Flashcards work when you use them to test yourself, and when you see each card again just before you would forget it. Here is how to do both, how to write cards that are worth reviewing, and what to put on a card when the answer is a formula, a proof step or a line of code.
By Marton Roux, who builds Studdle · updated
In short
Answer each card from memory before you flip it, grade yourself honestly, and see the cards you miss sooner than the ones you know: that is active recall with spaced repetition. Write one fact per card. For maths and physics, make cards for the conditions and the steps, not only the formulas.
Answer before you flip
Reading the answer side of a card feels like knowing it. Producing the answer before you look is what tests you, and what makes it stick. The Learning Scientists put it plainly in their guide to studying with flashcards: write or say your answer aloud, so you know you can actually formulate it.
Testing yourself has a second use: it shows you your weak spots. A card you hesitate on is information. Mark it, come back to it sooner, and rewrite it if the hesitation comes from the card rather than from you.
Space the reviews
Spaced repetition means you review a card again just as you are about to forget it: the cards you miss come back soon, the ones you know wait longer. On paper, the classic way is a set of boxes.
- Every new card starts in box 1.You review box 1 every session.
- A card you get right moves up a box.Each box after the first is reviewed less often than the one before.
- A card you miss goes back to box 1.However high it had climbed.
An app does the bookkeeping for you. Anki’s manual says its spaced repetition is based on the SM-2 algorithm. Studdle, ours, launching in early 2027, works out what is due today: what you miss comes back sooner, what you know waits longer.
How to write a good card
- check_circleOne fact per card. The University of Toronto Scarborough’s flashcard guide says it simply: less information per card is better.
- check_circleA real question on the front. “What does Ohm’s law state?” makes you produce an answer; “Ohm’s law” only invites a nod.
- check_circleA short answer on the back. If the answer is a paragraph, it is several cards.
- check_circleYour own words. Make your cards from your own course: writing them is part of learning it, and they use your lecturer’s notation.
- check_circleBoth directions, when it helps. Term to definition and definition to term, as the UTSC guide suggests: a problem can hand you either one.
Cards for maths, physics and computer science
A STEM course is not a list of vocabulary. Most of what you must recall is a formula with conditions, a method, or a step you keep getting wrong. These are the kinds of card worth making.
| Example card | |
|---|---|
| A definition | What is a group homomorphism? |
| A theorem’s conditions | When does the mean value theorem apply? |
| Which method | Which substitution for the integral of 1/(1 + x²)? |
| One step of a proof | Which identity links the integral of f² to its Fourier coefficients? |
| A unit or a sign | Unit of magnetic field? Sign of the work done on a gas? |
| Complexity | Worst-case time of quicksort, and the input that causes it? |
| What code does | What does this three-line loop print? |
For writing formulas on a card, the guide to maths flashcards with LaTeX covers the syntax and the apps that render it.
A session, step by step
- Start with the cards that are due.They are the ones you are closest to forgetting.
- Work in small batches.The UTSC guide suggests five to ten cards at a time, cycled until you know them.
- Answer aloud or on paper, then flip.An answer you only think tends to be vaguer than the one you would write.
- Grade yourself honestly.Good, OK or Bad. A generous grade only delays the card you need.
- Mix topics.Shuffling cards from different chapters builds links between them, and stops you answering from the card’s position.
- Add new cards in small numbers.Every new card is a review tomorrow and the days after. Add what you can keep up with.
What flashcards don’t replace
Flashcards make you remember what you need to have at hand: definitions, results, conditions, the step you forget. They don’t teach you to solve a problem you have never seen. In a maths or physics course, that still comes from exercises. Use the cards so that, in front of an exercise, you are not also hunting for the formula, and let the mistakes you make in exercises become new cards.
Common mistakes
- check_circleFlipping too early. Give yourself a real attempt before you look.
- check_circleCards that ask three things. You will grade them “OK” forever and never know which part you miss.
- check_circleStarting the night before. The UTSC guide suggests starting at least two weeks before a test.
- check_circleKeeping bad cards. A card you misread every time is a badly written card. Rewrite it or delete it.
- check_circleReviewing only what you know. It feels good and teaches you nothing new. The cards you miss are the session.
Answer first, then flip.
Training that knows what is due
Studdle launches in early 2027. It works out what is due today; you reveal the answer, grade yourself Good, OK or Bad, and what you miss comes back sooner. Pebble drafts the cards from your lecture PDF, and you read each one before you keep it.
Common questions
Are flashcards a good way to study?add
Yes, if you use them to test yourself. Answering from memory and then checking is what makes them work, because it shows you what you can actually recall. They suit definitions, formulas and the conditions around them, and they work best alongside the exercises that teach you to use them.
How long should I study flashcards a day?add
Long enough to clear the cards that are due, which an app counts for you. The University of Toronto Scarborough’s guide suggests starting at least two weeks before a test.
Should I make my own flashcards?add
Mostly, yes. Writing a card makes you decide what matters and say it in your own words. If a tool drafts them for you, check and rewrite each one before you keep it.
How long does it take to memorise 100 flashcards?add
It depends on the cards more than the number. Short definitions settle quickly; cards on proofs and methods take longer, because each answer holds more. With spaced repetition you don’t need to count: the cards you know stop coming back often, and the ones you don’t keep showing up.