Memory

Spaced repetition: how it works and a simple study schedule

By Studycamp · September 20, 2026 · 13 min read

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Spaced repetition means you review material several times, with the gaps between reviews getting longer each time. You study something, then come back after a day, then a few days, then a week or two. Each time you try to recall it before you look at it. It works because your brain holds onto things better when you nearly forget them and then retrieve them.

You don't need an app to do it. A calendar and a stack of index cards are enough.

Key takeaways

Spacing your study sessions beats cramming. In a set of flashcard experiments, 90% of participants learned more with spaced practice than with massed practice (Kornell, 2009).
The best gap depends on how far away your test is. Far-off tests call for longer gaps, and there is no single perfect interval.
A simple starting schedule is reviews at 1, 3, 7, 14, and 30 days after you first learn something. Treat it as a suggestion and adjust it.
The Leitner system is spaced repetition with paper cards and five boxes. It costs almost nothing, and setup should take about ten minutes (our estimate).
Studycamp turns your course files into flashcards, and its calendar can hold your review days. It has no built-in review scheduler, so you pick the dates from this post's schedule.
Apps like Anki pay off for big, long-term piles of facts. For one exam a few weeks away, a calendar and a card box are usually enough.

How spaced repetition works

Spacing means you spread study over time instead of one block. Repetition means you come back to the same material. Add one rule: every review should be an attempt to remember, not a re-read. Close the notes, try to answer the question, then check. That is active recall, and spaced repetition is what you get when you schedule it over days and weeks.

This matters because rereading feels productive and often isn't. A large review of ten common study techniques rated practice testing and distributed practice as the two with "high utility," and rated highlighting and rereading as low utility (Dunlosky et al., 2013).

The forgetting curve and the spacing effect

In the 1880s the psychologist Hermann Ebbinghaus memorized lists of nonsense syllables, then tested how much effort it took to relearn them after different delays. He found that forgetting was fast at first and then slowed down. That drop is the forgetting curve.

Ebbinghaus tested himself, using meaningless syllables. In 2015, researchers at the University of Amsterdam repeated his experiment with one subject who spent about 70 hours learning and relearning lists at the same delays (20 minutes up to 31 days). The curve matched closely. It also wasn't perfectly smooth. There was a small jump upward starting around the 24-hour mark, which the authors linked to possible effects of sleep (Murre and Dros, 2015).

So the curve is real, but it's one person and one kind of material. Don't treat any exact "you forget X% in a day" figure online as a law.

The stronger evidence comes from the spacing effect. In 2006, Cepeda and colleagues pulled together 839 assessments of distributed practice from 317 experiments in 184 articles. They found that the study gap that produced the best retention grew as the delay before the final test grew (Cepeda et al., 2006). In plain terms: if your test is far away, wider gaps between study sessions work better.

Another finding fits students. In Kornell's flashcard experiments, 90% of participants learned more in the spaced conditions than the massed ones, while only 6% showed the reverse (Kornell, 2009). It helped most of them.

Spacing can feel worse while you're doing it. Reviews after a gap are harder because you've forgotten some of it. That difficulty is part of why spacing works, and part of why cramming feels more efficient than it is.

How far apart should reviews be?

There is no single correct answer, and researchers say so themselves. A 2022 review of spacing and retrieval practice by Carpenter, Pan and Butler states that there is no universal ideal spacing schedule. Effective schedules, they write, leave enough time between sessions that the material is still familiar but not fresh in mind (Carpenter et al., 2022). Carpenter's advice to learners is similar: leave enough time that the material is "not fresh in your mind when you come back to it" (Retrieval Practice).

There is one useful rule of thumb from a large experiment. Cepeda and colleagues taught more than 1,350 people a set of facts, gave a review after a gap of up to 3.5 months, and tested them up to a year later. The best gap was about 20 to 40% of the delay for a test one week away, and about 5 to 10% for a test one year away (Cepeda et al., 2008).

In days, that comes out as follows (this is arithmetic from their percentages, not a table from the paper):

Your test is in	A good gap between two study sessions
1 week	about 1 to 3 days
1 year	about 2.5 to 5 weeks (18 to 36 days)

Two limits apply. That study used trivia-style facts, not calculus or essays, and it tested one review, not a long chain. Use it as a sanity check.

A simple DIY schedule

A starting schedule you can copy: after you first learn a topic on Day 0, review it on Day 1, Day 3, Day 7, Day 14, and Day 30. This exact pattern is our suggestion, not a tested optimum.

University learning centers publish close cousins of it. The University of Arizona describes a 1-3-7-14 plan (review on day 1, 3, 7 and 14 after you first learn something). Birmingham City University describes a 2-3-5-7 method that counts back from your exam date, with gaps of 2, 3, 5 and 7 days before the last session. The shape is the same: short gaps first, longer gaps later.

Say you learn a lecture on cell respiration on Monday.

Day	What you do	Time
Day 0 (Mon)	Attend the lecture, make 10 to 15 questions from your notes	20 min
Day 1 (Tue)	Answer the questions from memory, mark the misses	10 min
Day 3 (Thu)	Answer again, only look up the ones you miss	10 min
Day 7 (next Mon)	Answer again, mix in questions from other lectures	10 min
Day 14	Answer again	5 to 10 min
Day 30	Final check before you let it go, or keep it until the exam	5 to 10 min

Rules that keep this simple:

Make questions, not summaries. A card that says "Why does the citric acid cycle need oxygen indirectly?" beats a paragraph you'll skim. More on this in how to make flashcards.
Answer before you look. Say it or write it down first. If you peek early, you've just reread.
Missed it? Shorten the gap. If you blank on a card at Day 7, review it again in a day or two.
Nailed it? Stretch the gap. Easy material can skip ahead to Day 21.
Fell behind? Review only what's due now. A late review still counts.

The Leitner system: spaced repetition with paper cards

The Leitner system is a way to run spaced repetition with a box of physical cards. The German science writer Sebastian Leitner described it in his book So lernt man lernen ("How to learn to learn"), published by Herder in 1972 (Google Books record). Many people today run it on fixed review days, which is easier to follow.

You need index cards and five envelopes, rubber-banded stacks, or a shoebox with dividers.

Setup

Label five boxes 1 to 5.
Write one question on the front of each card and the answer on the back.
Put every new card in Box 1.

Review days (one version that mirrors the schedule above)

Box	Review how often
Box 1	Every day
Box 2	Every 3 days
Box 3	Every week
Box 4	Every 2 weeks
Box 5	Every month

The one rule

Get a card right: move it up one box.
Get a card wrong: move it back to Box 1.

Cards you know drift out of your daily pile. Cards you keep missing stay in front of you, so your time goes to what you don't know yet.

A day in the box. Monday you write 12 cards and drop them in Box 1. Tuesday you go through Box 1. Nine right, so they move to Box 2. Three wrong, so they stay in Box 1 and get another look Wednesday. Thursday you go through Box 1 again. Friday is Box 2's turn, so you do Box 1 and Box 2.

Where it falls short. Paper boxes get fiddly past a few hundred cards, and you have to remember which box is due today. A phone reminder helps. For one course over a semester that's fine. For a huge deck, it isn't.

If you'd rather skip the writing, Studycamp flashcards can be generated from your uploaded files, and you review them by flipping and shuffling. There is no built-in review scheduler, so you pick the review days yourself.

Spaced repetition apps: worth it or overkill?

Studycamp is the place to make the cards: it builds a deck from your own files. It has no review scheduler, so you run the spacing yourself with a calendar. If you want software to schedule reviews, use an app built for that. Anki is the best-known one.

A spaced repetition app does the bookkeeping for you. You rate each card after you answer, and the app decides when it comes back. Anki's desktop version is free, AnkiDroid on Android is free, and AnkiMobile on iOS is a paid app (per Anki's own site, as of September 2026). Anki also offers an optional scheduler called FSRS, and its default target is that you remember 90% of cards when they come up for review (Anki manual, as of September 2026).

Apps are worth it when:

You have hundreds or thousands of facts to keep for months or years, like anatomy terms, a language, case names, or drug names.
You'll review a little every day and can keep that habit going.
Your exam is months away, so the long gaps have room to work.

Apps are overkill when:

You have one exam in two or three weeks and 60 key terms. A card box or a plain checklist does the same job.
The course is mostly problem-solving. Practice problems, spaced out, beat memorizing formulas on cards.
You've never studied with flashcards before. Try a paper box for a week and see if the habit sticks.

Other flashcard apps exist, such as Quizlet and Brainscape. If scheduling matters to you, check each one's current documentation, since features change. Whichever you pick, a bad card scheduled perfectly is still a bad card.

Fitting spaced repetition around an exam date

Work backward from the exam. Every topic should get its reviews before the exam, with the last one landing in the final week.

Say your exam is 5 weeks (35 days) away and you learn a new chapter each week.

Chapter	Learned	Reviews
Chapter 1	Day 0	Days 1, 3, 7, 14, 30
Chapter 2	Day 7	Days 8, 10, 14, 21, plus a final review around Day 33
Chapter 3	Day 14	Days 15, 17, 21, 28, plus a final review around Day 33

The reviews overlap. On Day 14 you're reviewing Chapters 1 and 2 and learning Chapter 3. That's normal. Later chapters get fewer reviews because less time is left, so end with one final pass.

Put it on a calendar. Add each review as a 10 to 20 minute block, in any calendar app or on paper. Reviews that aren't scheduled tend to get skipped. Studycamp's calendar works for this too, and the steps are below.

Leave the last two days light. In the final 48 hours, do one pass over the cards you still miss. Don't start new material. The rest of your prep is covered in how to study for exams.

Common mistakes

Rereading and calling it review. If you didn't try to recall it first, it doesn't count.
Making cards you can't answer. "Photosynthesis" isn't a question. "What are the inputs and outputs of the light reactions?" is.
Making too many cards. Every card is a debt. Cut cards you'd never be tested on.
Expecting it to feel easy. If every review is smooth, your gaps are probably too short.

Spacing works best next to retrieval and good notes. For the whole routine, read how to study effectively.

Space your reviews in Studycamp

Studycamp doesn't schedule reviews for you. You choose the dates yourself, and the app holds the cards and the calendar. Here is one way to set it up:

Create a course workspace and upload your lecture slides, PDFs, and notes.
Generate a flashcard deck from those files. One deck per chapter keeps things tidy.
Open the calendar and add the review dates from the schedule above: Day 1, 3, 7, 14, and 30 after you first learn a chapter. Add a countdown to the exam so the last pass has a fixed date.
On each review day, open the deck. Answer out loud before you flip a card, shuffle so the order changes, and resume where you left off if you get interrupted.
On the last pass, take a quiz from the same files. You get multiple-choice questions and an explanation after each answer.

If you miss a card, nothing moves it up the queue. Add an extra review to the calendar yourself, as in rule 3 above.

Start studying free on the free plan (3 workspaces, 1 GB of storage, and 1,500 AI credits a month), and see pricing if you want more.

FAQ

How long does spaced repetition take to work?

Spacing tends to pay off by test day, not right after a session. Reviews after a gap feel harder than rereading, and that's expected. Our suggestion is to start two to three weeks before an exam so the longer gaps have room to fit. The research behind the spacing effect ties the best gap to how far away the test is (Cepeda et al., 2006).

What is the best spaced repetition schedule?

There isn't a single best one. A common starting point is Day 1, 3, 7, 14, and 30. The right gaps depend on how far off your exam is and how hard the material is. Carpenter and colleagues suggest leaving enough time that the material is familiar but not fresh in mind (Carpenter et al., 2022).

Is the Leitner system still worth using?

Yes, if you have a modest number of cards and want no software. It follows the same principle as apps: cards you know show up less often, cards you miss show up more. It gets awkward with very large decks.

Do I need Anki for spaced repetition?

Not necessarily. Anki is a good fit for large, long-term collections of facts. For a single course or an exam a few weeks away, a paper Leitner box or a calendar with review days marked on it can work. Start simple and move to an app if the cards pile up.

If you want a place to block out review days, Studycamp has a calendar for that.