How to make good flashcards: rules and examples

What makes a flashcard effective?

A good flashcard asks one clear question and has one short answer that you can mark right or wrong in a second. That sounds obvious, but most cards that students make break it. They copy a paragraph from the textbook onto the back, or put a whole topic on the front ("Mitosis?"). Then the review turns into rereading, and the card is marked "right" whenever it looks vaguely familiar.

Piotr Wozniak, who wrote the SuperMemo software, called this the minimum information principle: phrase each item as simply as possible, because simple items are easier to recall reliably and can each be scheduled at their own pace. His 1999 list of twenty rules for formulating knowledge is still the best-known guide to card writing.

Rule 1: one idea per card

If the answer has three facts, you have three cards. Split cards are faster to review, and when you miss one, the schedule brings back just the part you missed.

Rule 2: ask a question with one right answer

A card front that is just a word ("Photosynthesis") invites a vague answer. A front that is a specific question gets a specific answer you can check.

Cloze cards (fill in the blank) are a quick way to do this: "The powerhouse of the cell is the ____." Blank out only one key word per card.

Rule 3: study in both directions when you need both

Knowing that mitochondrion means "the organelle that makes most of the cell's ATP" is not the same as being able to come up with mitochondrion when an exam describes it. Recognition and production are different skills. For vocabulary, terms and formulas you must write from memory, review the card both ways: term to definition, and definition to term.

You do not need to write two cards for this. In StudyBrix flashcard decks you can tick "Show definitions first" to flip the direction, and you can make your own deck from the flashcards page. Paper cards work too: shuffle and turn half the pile over.

Rule 4: add an example to abstract cards

Definitions on their own are easy to memorize and hard to use. A concrete example on the back, or a card that asks for one, ties the word to something you can picture or calculate.

Even better, write a few cards that are tiny problems. "d/dx of e^(3x) = ?" (answer: 3e^(3x)) tests whether you can apply the chain rule, not just recite it.

Rule 5: avoid long lists on one card

Lists are the hardest thing to hold on a flashcard. Wozniak advised avoiding sets (unordered lists) and long enumerations (ordered ones), and noted that sets of more than about five items are very hard to learn without restructuring them. You either remember all seven items or you do not, and you will usually mark yourself generously.

Break the list up instead:

• Overlapping cloze. For an ordered list like the stages of mitosis, make cards such as "Prophase, ____, anaphase" and "Anaphase, ____, ...". Each card tests one link in the chain.
• Count card plus item cards. One card asks "How many ...?" and separate cards ask for each item with a hint.
• Group into a story or acronym if the order matters, then test the acronym on one card and each letter on its own card.

More rules that save time

A few smaller habits make a deck easier to live with over a whole term.

• Understand first, then make the card. A card for a concept you do not get becomes a string of words you memorize and cannot use.
• Write cards in your own words. Copy-pasting from slides is fast and makes weaker cards.
• Add a source or tag. "Lecture 7" or "Ch. 4" on the card makes it easy to look things up when you keep missing it.
• Delete or fix leeches. A card you have missed eight times is usually badly written. Rewrite it, split it, or add an example.
• Use images where shape matters. Anatomy diagrams, molecular structures and graphs are often clearer as an image with one label hidden.

How many cards per lecture?

A typical first-year lecture produces somewhere around 10 to 25 good cards. If you are making 60, you are probably copying slides. If you are making 3, you are probably writing paragraph cards. Make them the same day, review them the next day, and let the schedule do the rest; see spaced repetition flashcards for the gaps to use and active recall vs rereading for why answering beats looking.

If you want examples of short, one-idea cards to copy the style of, browse a deck like Calculus I: derivatives or General chemistry I. Each card has a term, a one-sentence definition and, where it helps, a worked example.