Spaced Repetition: How It Works and a Revision Schedule You Can Use

Spaced repetition is a study method where you review the same material several times with growing gaps in between, for example after one day, three days, a week, two weeks and a month. Each review comes just as you're starting to forget, which makes the memory stronger and slower to fade than if you had studied it all at once.

It is the opposite of cramming, and it's one of the most reliable findings in memory research. This guide explains where the idea comes from, what the research says, how to run it with paper cards or an app, and gives you a revision schedule you can copy today.

What is spaced repetition?

Spaced repetition has two parts:

1. Repetition: you see the material more than once.
2. Spacing: the repeats are spread out over days and weeks, with each gap a little longer than the last.

Studying something five times on Sunday night is repetition without spacing. Studying it once on each of five different days, a few days apart, is spaced repetition. Same effort, very different results.

The effect behind it is called the spacing effect, or distributed practice. Spaced repetition is just a system for using it on purpose.

What is the forgetting curve?

In 1885 the German psychologist Hermann Ebbinghaus published Über das Gedächtnis, translated into English as Memory: A Contribution to Experimental Psychology. He spent years memorising lists of nonsense syllables and testing himself on how long it took to relearn them after different delays.

His results traced what's now called the forgetting curve. Forgetting is fastest right after you learn something, then slows down. A lot of what you learn on Monday is gone by Tuesday, but what survives to Friday tends to hang on longer.

He also found that relearning was faster than learning from scratch, and that each round of review made the material last longer. That's the core idea of spaced repetition: every review resets the curve and makes it flatter.

Ebbinghaus's exact numbers came from one person learning nonsense syllables, so don't treat them as a precise rule for learning biology. The shape of the curve is the useful part.

What does the research say about spacing?

A lot. The spacing effect has been studied for over a century.

The most widely cited review is Cepeda, Pashler, Vul, Wixted and Rohrer (2006), published in Psychological Bulletin. They pooled results from a large number of experiments on distributed practice and found that spacing study sessions apart consistently produced better long-term recall than massing them together.

They also found that the best gap depends on how long you need to remember something. If the test is tomorrow, short gaps are fine. If the test is months away, longer gaps work better. That's useful for planning: a final exam at the end of the year can handle much bigger gaps than a quiz next week.

The review by Dunlosky and colleagues (2013) in Psychological Science in the Public Interest rated distributed practice as one of only two highly useful study techniques. The other was practice testing, which is why spaced repetition and active recall are usually used together.

Why does spacing work?

Researchers still debate the exact reasons, but a few ideas are widely discussed:

• Effortful retrieval. When you review after a gap, you have to work a bit harder to remember. That effort strengthens the memory more than an easy review straight after learning.
• Different contexts. Reviewing on different days, in different moods and places, gives you more routes back to the memory.
• Less boredom. Fifth time through in one evening, your attention has gone. Fifth time through on a new day, it's fresh.

How do you use spaced repetition? A practical schedule

Here's a simple schedule that works for most school and uni content. Day 0 is the day you first learn something.

A caveat: these intervals are a rule of thumb, not a scientific formula. Nobody has proven that day 3 is better than day 4. What matters is that the gaps grow and that you don't let a topic go untouched for months. Adjust freely:

• If you forgot most of it at a review, shorten the next gap. Go back a step.
• If it was easy, lengthen the next gap. Skip a step.
• If your exam is close, compress the whole thing.

Notice that reviews get shorter as gaps get longer. Most of the work happens early.

What does a week look like with multiple topics?

The tricky part is that new topics keep arriving while old ones need reviewing. Here's what it looks like when you learn one new topic each weekday.

The reviews never pile up much, because each one is short. A good habit is to do reviews first, at the start of each session, before new content. They're quick, they warm you up and they're the part you're most likely to skip if you leave them until last.

To fit this into a full week across all your subjects, see our guide on how to make a study timetable.

What is the Leitner system?

The Leitner system is a way to run spaced repetition with paper flashcards and a few boxes. It was popularised by the German science journalist Sebastian Leitner in the 1970s.

You need five boxes (or five envelopes, or five rubber bands). Each box is reviewed on a different schedule.

How it works:

1. All new cards start in Box 1.
2. When you review a box, try to answer each card from memory before flipping it.
3. Right: the card moves up one box, so you'll see it less often.
4. Wrong: the card goes all the way back to Box 1, no matter where it was.
5. Cards that make it out of Box 5 are retired, or checked once more before the exam.

The beauty of the system is that it automatically spends your time where you need it. Cards you know drift to the back. Cards you keep missing stay in front of you every day.

Should you use Anki or another app?

Apps take the date tracking off your hands. Anki is a widely used flashcard program built around spaced repetition: each time you see a card you rate how well you remembered it, and Anki decides when to show it next. Other flashcard apps, such as Quizlet, also offer review modes.

Apps are a good fit when:

• you have hundreds or thousands of facts (vocab, anatomy, pharmacology, law cases)
• you want to review on your phone in small gaps
• you'd lose track of paper cards

Paper is a good fit when:

• you have a manageable number of cards per subject
• writing cards by hand helps you process them
• your phone is the thing you're trying to stay away from

Either way, the rules are the same: one idea per card, answer before you flip, and do your reviews every day rather than letting them pile up. A backlog of 400 overdue cards is how most students quit.

How to use spaced repetition by subject

Content-heavy subjects

Biology, legal studies, history, business, psychology and anything with lots of definitions are perfect for flashcards on a schedule. Turn every dot point into a question as you learn it.

Maths and physics

You can't flashcard your way through calculus, but you can space problem types. Each practice set should include a few questions from topics you did one, two and four weeks ago. This also mixes up the order of problems, which is the idea behind interleaving.

English and essay subjects

Space your quotes and key evidence with cards. Then space your essay practice: plan a response to a question on a text, then come back to a different question on the same text a week later.

Languages

Vocab is where spaced repetition is most famous. Add a sentence or phrase, not just a single word, and practise in both directions.

How do you use spaced repetition before an exam?

The ideal is to start in week one of term. Real life doesn't always cooperate. Here's how to scale it to the time you have.

Even when time is short, two reviews on different days beat the same total time in one block. If you're truly out of time, our guide on how to cram for an exam covers damage control.

What are the most common spaced repetition mistakes?

Rereading instead of recalling at each review. Spacing a passive review is better than not spacing it, but the big gains come from testing yourself.

Making too many cards. If you add 100 new cards a day, you'll have hundreds of reviews a day within a fortnight. Add what you can sustain.

Skipping days. The system relies on reviews happening roughly on time. A few missed days creates a backlog. Short daily sessions beat long weekly ones.

Treating the schedule as sacred. Day 7 versus day 8 does not matter. Consistency does.

Only reviewing the easy stuff. Cards you keep missing need more attention, not less. The Leitner rule of sending missed cards back to Box 1 exists for a reason.

Never retiring anything. If a card has been right every time for months, check it less or drop it before the exam.

How to keep up spaced repetition with StudyDork

Spaced repetition only works if you actually show up for reviews, so the hard part is the habit, not the theory. StudyDork doesn't schedule flashcards (keep using paper, Anki or whatever you like for that), but it can help you turn up every day.

• A daily streak. Finishing one focus session a day builds your streak, so a short review session keeps it alive. You can see this month's activity on a heatmap, explained on the progress page.
• Short sessions. Reviews are quick, which suits a 20 minute Pomodoro block on the free plan. Put reviews in the first block and new content after.
• Subjects. Subjects are free and unlimited, so you can log review time against each class. StudyDork Pro adds Subject Stats to show the breakdown.
• Calendar locks. With StudyDork Pro, Auto-Lock Calendar can turn events in Google Calendar or Apple Calendar into focus sessions that lock your apps, handy if you put daily review slots in your calendar.

Small reviews, big payoff

Spaced repetition asks for very little at a time. Ten or fifteen minutes of review, at the right moments, keeps a topic alive for months. Cramming asks for a huge effort and gives most of it back within a week.

Start with the next thing you learn. Make a few questions about it, then write the dates for day 1, 3, 7, 14 and 30 in your diary. Show up for those five short reviews, and you'll walk into the exam remembering it instead of relearning it.