Spaced repetition schedule: how far apart to review, with examples

A good spaced repetition schedule reviews new material about a day after you learn it, then again after a few days, then after a week or two, with each gap longer than the last, and resets a topic to a short gap whenever you get it wrong. The right spacing depends on when the exam is: the further away the test, the longer the gaps can be. This guide covers the research on gap length, schedules for an exam in a week, a month and three months, the 2-3-5-7 rule and where it falls short, and how to run a schedule without managing it by hand.

What spaced repetition is

Spaced repetition means coming back to the same material in several sessions separated by gaps, instead of in one long session. Each session should be a test: you try to recall the material before you look at it. The gap gives you time to start forgetting, which makes the recall harder and the memory more durable. It is the opposite of cramming, where you go over the same material many times in one evening.

The evidence is broad. Cepeda and colleagues' synthesis of spacing research found that spaced study beat massed study in nearly every condition they examined [1]. Dunlosky and colleagues rated distributed practice as one of only two high-utility techniques out of ten they reviewed, alongside practice testing [2]. The two belong together, and the method below assumes every review is a recall attempt.

What is the best schedule for spaced repetition?

The most useful study on this question taught more than 1,350 people a set of facts and gave them one review after a gap of up to three and a half months. A final test came after a further delay of up to a year [3]. Cepeda and colleagues found that the best gap depends on how long you need to remember. For a test a week away, it was about 20 to 40 percent of the time until the test. For a test a year away, it fell to about 5 to 10 percent. A gap that is too short wastes the review. A gap that is too long means you have forgotten too much to recall it.

The figures are approximate. The paper's own conclusion is that the gap should grow with the retention interval. The other rule from the literature is to expand the gaps as material gets easier: one review after a day, the next after a few days, the next after a week or two.

Three schedules you can copy

1. Exam in one weekLearn the material on day 1. Recall it on day 2, day 4 and day 6. Rest on day 7, with a short look over anything you missed on day 6. If you have several topics, stagger them by a day so you are never reviewing everything at once.
2. Exam in one monthLearn on day 1. Recall on day 2, day 5, day 12 and day 21, then a final mixed review two or three days before the exam. Anything you miss goes back to a two-day gap before rejoining the schedule.
3. Exam in three months, or a whole courseLearn each week's material that week and recall it the next day. Then review it after one week, three weeks and six weeks, and in a mixed final review in the last fortnight. A weekly calendar block for older topics keeps the pile from growing.

In each case, a review means closing the notes and producing the answers: flashcards answered before flipping, a blank-page blurt, a practice quiz. Rereading on day 4 is still rereading.

The 2-3-5-7 rule, and the 2-7-30 rule

The 2-3-5-7 rule, common on UK revision sites, schedules reviews on day 2, day 3, day 5 and day 7 after first learning something. It gives you four spaced sessions in a week, which is a reasonable plan for a test about a week away, and it is easy to remember. The 2-7-30 rule reviews after two days, a week and a month, which suits material you need for a term.

Both are fixed schedules, and fixed schedules treat every topic the same. The topic you got right three times in a row gets as many reviews as the one you keep failing. Adaptive schedules fix that.

Fixed schedules versus adaptive ones

An adaptive schedule sets the next gap from how the last review went. Get a card right and the gap grows. Miss it and the card comes back soon. The idea goes back to the Leitner box: index cards move to a box reviewed less often each time you get them right, and back to the first box when you miss them. Flashcard apps automate the same logic per card.

Adaptive scheduling suits facts on cards. For larger chunks, such as a lecture, an essay topic or a process you need to explain, a calendar with the fixed schedule above is simpler and works fine. Most students need both: cards for the terms and formulas, calendar slots for the topics.

Running a schedule in Bord

Flashcards in Bord schedules each card for you. Ask for a deck on a topic, your slides or a lecture recording, or write your own cards, and study by recalling, flipping and marking each card. When you mark a card "Again", it comes back in about ten minutes. When you mark "Got it", it waits a day, then three days, then longer each time, and cards you know well move out to a week or more. The scheduler is SM-2 style: each card carries an ease factor that rises when you get it and drops when you miss it, so hard cards stay on short gaps. Progress saves with the board, so the schedule follows you across devices. Studying a deck does not use your weekly allowance; only making one does.

For the topic-sized reviews, keep each course on one board with its sources, and on each review day ask Quizbook for a round on that week's material. It grades the round, tells you what to revise, and the next round targets what you missed, which gives you the adaptive part for whole topics. If you are short of time, our seven-day finals plan is the one-week schedule above, worked out day by day.

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