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Spaced repetition schedule: which intervals, and how to plan them

Published 6 October 2026 · Updated 6 October 2026 · by the Paced team

What spaced repetition is

You study a topic once, then review it after a short gap, then after a longer one, and so on. Each review comes back when the material has started to fade but is still retrievable. The idea goes back to Hermann Ebbinghaus, who measured his own forgetting in 1885; Murre and Dros repeated his experiment in 2015 and obtained similar results: forgetting is fastest in the first hours and days, then slows down.

Two findings make spacing worth planning. First, the spacing effect: the same total study time produces better long-term retention when it is spread out. Second, the testing effect: a review in which you try to recall (questions, a blank page, flashcards) does more for delayed recall than rereading. Dunlosky and colleagues (2013) reviewed ten study techniques and gave a high-utility rating to these two only, distributed practice and practice testing; rereading and highlighting came out as low utility.

What the research says about intervals

• The best gap depends on the deadline. Cepeda and colleagues (2006) pooled 839 assessments from 317 experiments: the gap that maximised retention increased as the retention interval (the time until the test) increased.
• As a share of the time left, it shrinks. In a study of more than 1,350 learners with review gaps of up to 3.5 months and final tests up to a year after the review, the best gap was about 20–40% of the test delay when the test came a week later, but only about 5–10% when it came a year later (Cepeda et al., 2008).
• A late review still counts. In the same study, lengthening the gap first raised final scores, then lowered them only gradually. A review that comes a few days late is not wasted.
• Recall beats rereading. On tests two days and a week later, students who practised recall remembered more than students who restudied the same text, even though restudying made them feel more confident (Roediger & Karpicke, 2006). Repeated testing had a large effect on delayed recall; repeated studying after learning had none (Karpicke & Roediger, 2008).

Three schedules you can use

These are the built-in paces of Paced, written as days after the first study (D0). They are practical choices consistent with the findings above, not values taken from one study. Light suits material you need for a long time with fewer reviews; Intensive brings reviews closer together, which fits a nearer deadline.

On the Standard pace, a topic first studied on a Monday comes back on these days. The durations assume a 2 h 30 first study and the default review curve of Paced: the first review takes 30% of the first study's time, each later one 4 points less, never under 10% (all adjustable).

Why schedules break: reviews pile up

Each topic you add brings its own reviews with it. On the Standard pace with the default durations, one 2 h 30 topic adds 8 reviews and 3 h 30 of review time spread over 240 days. Add 5 such topics a week and, once the first ones reach their last review, reviews alone average about 2 h 30 a day, on top of about 1 h 47 of new study (our calculation, from the figures above). A paper calendar or a spreadsheet does not show you this until the week it no longer fits.

How to plan a spaced repetition schedule

1. List what you study as topics (a chapter, a lecture, a system), each with a realistic first-study time.
2. Write down the time you really have each day once classes, work, shifts and travel are removed, and your days off.
3. Pick a pace from your deadline: the closer the exam, the shorter the gaps.
4. Make each review a recall: questions, cards or a blank page, then check against your notes.
5. Check the load before it lands: add up the reviews due each day, not just the new topics.
6. When you fall behind, reschedule instead of deleting: see how to catch up on reviews.

Studying medicine? The same method, applied to a curriculum and a board exam: how to build a medical school study schedule.

Questions

Sources

1. Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354–380. Meta-analysis of 839 assessments in 317 experiments: the gap that maximises retention grows with how long you need to remember.
2. Cepeda, N. J., Vul, E., Rohrer, D., Wixted, J. T., & Pashler, H. (2008). Spacing effects in learning: A temporal ridgeline of optimal retention. Psychological Science, 19(11), 1095–1102. More than 1,350 learners, review gaps up to 3.5 months, final tests up to a year later.
3. Ebbinghaus, H. (1885). Memory: A Contribution to Experimental Psychology (English translation by H. A. Ruger & C. E. Bussenius, 1913). Classics in the History of Psychology, York University. The original forgetting-curve experiments, measured by the time saved when relearning.
4. Murre, J. M. J., & Dros, J. (2015). Replication and Analysis of Ebbinghaus' Forgetting Curve. PLoS ONE, 10(7), e0120644. One subject, 70 hours of learning and relearning after 20 minutes to 31 days: results similar to Ebbinghaus's.
5. Roediger, H. L., & Karpicke, J. D. (2006). Test-enhanced learning: Taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255. On tests two days and one week later, practising recall beat restudying the same text.
6. Karpicke, J. D., & Roediger, H. L. (2008). The critical importance of retrieval for learning. Science, 319(5865), 966–968. Repeated testing had a large effect on delayed recall; repeated studying after learning had none.
7. Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J., & Willingham, D. T. (2013). Improving students' learning with effective learning techniques: Promising directions from cognitive and educational psychology. Psychological Science in the Public Interest, 14(1), 4–58. Review of 10 techniques: practice testing and distributed practice rated high utility; rereading and highlighting low.