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The 2-3-5-7 revision method: what it is, what it misses, and a calculator

Published 23 October 2026 · Updated 23 October 2026

Sources checked on 23 October 2026 by Alexandre Doumergue, founder of Paced.

What the 2-3-5-7 method says

You learn a topic on day 0. You review it on 4 later days whose numbers are 2, 3, 5 and 7. Each review is a short, active session: you try to recall the topic before you look at your notes. After the last review the method says nothing more, which is why it is often taught for exam season, when the test is a week or two away. A 2357 study method calendar is therefore just 4 dated events per topic.

The 2357 revision method is widely taught on school and university study-skills pages. We found no study that tested this exact sequence (a PubMed title and abstract search for “2-3-5-7 method”, “2357 method” and “2-3-5-7 rule” returned no record, 23 October 2026). The idea behind it — spreading reviews out instead of massing them — is one of the most replicated findings in learning research; the specific numbers 2, 3, 5 and 7 are a convention.

The three ways people read “2, 3, 5, 7”

Pages that teach the method do not agree on what the numbers count. All three readings are in circulation:

The calculator below uses reading A by default and lets you switch. Whichever you pick, write it down and keep it: the point is to come back on planned days, not to argue about day 1.

How long is each review? If the first study took 2 h 30, Paced's default review curve gives 45 min, 39 min, 33 min, 27 min for the 4 reviews — 2 h 24 in total. Reviews shrink because you are recalling, not relearning. These are our planning defaults, not values from a study; you can change them in the calculator.

Does the 2-3-5-7 method work?

What the research supports

• Spacing beats massing. A meta-analysis of 839 assessments from 317 experiments found that spreading study over time improved retention compared with massing it, and that the best gap grows with how long you need to remember (Cepeda et al., 2006).
• The gap should match the deadline. In a study of more than 1,350 learners, with gaps of up to 3.5 months and final tests up to a year later, the best gap grew with the time to the test (about 20–40% of it for a test a week away, 5–10% for a test a year away) (Cepeda et al., 2008).
• Recall, not rereading. Students who practised recalling a text remembered more of it two days and one week later than students who reread it (Roediger & Karpicke, 2006). The 2-3-5-7 sessions only help if they are recall sessions.

So the method is sound for what it covers: 4 early reviews in the first week, in the first days after learning, where measured forgetting is steepest (Ebbinghaus, 1885; Murre & Dros, 2015 — see the forgetting curve).

Where it falls short: the exam is weeks away

The 4 reviews all land in the first week. If the exam is in 6 weeks, the method leaves a long silence before it. For a topic first studied 42 days before the exam:

Our calculation from the paces. The research above suggests that the last gap matters when the test is weeks away, but it does not give one right number. The practical rule: if the exam is more than about two weeks away, keep reviewing after day 7, on gaps that grow until the exam. The calculator's “keep spacing” box does that with the Standard pace's later days.

What 2-3-5-7 costs in a real week

Take three new topics a week, 1 h 30 each for the first study, on six study days. Our calculation:

2-3-5-7 levels off at 4 h 18 of reviews a week from week 2, because every topic is finished after 7 days. The Standard pace costs 39 min more a week from week 5, and in exchange keeps a review at each of its later days for every topic. Whether that fits depends on the hours you actually have — which is the question the full calculator answers.

2-3-5-7 backwards from your exam date

To fit all 4 reviews of reading A before the exam, with the day before the exam left free, the first study must happen at least 8 days before the exam. With an exam on Friday 4 December 2026, the last day to start a new topic on 2-3-5-7 is Thursday 26 November 2026. For a whole list of topics, enter the exam date in the calculator below, then your first study dates: it flags every review that would fall on or after the exam day.

What to do in each 2-3-5-7 session

1. Close the notes. Write or say what you remember of the topic: headings, definitions, the steps of a method, a worked problem.
2. Check. Open the notes and mark what was missing or wrong.
3. Fix the gaps only. Reread what you missed, not the whole chapter.
4. Stop. A session that runs long eats the next topic's time. The minutes in the calculator are a budget, not a target.

If you miss a day, do the review the next day and keep the following ones where they are. A late review still counts. The blank-page version of the first step is described in the blurting method.

2-3-5-7 calculator

Enter the date of your first study, choose a reading of 2-3-5-7, and get the 4 review dates with their lengths. Add an exam date to count backwards. Download the dates as a calendar file (.ics) or a spreadsheet (CSV). Nothing you enter is sent to us. To put the dates in your calendar app step by step, the calculator exports the same files for any pace.

Google Calendar and Google Sheets are trademarks of Google LLC; Outlook and Excel, of Microsoft Corporation; Apple Calendar, of Apple Inc.; Notion, of Notion Labs, Inc. Paced is not affiliated with any of them.

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. 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.
4. 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.
5. 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.

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