Ace
Short answer: review new material 1 day after learning it, then after 3 days, 7 days, 14 days and 30 days, testing yourself each time instead of re-reading. If you get an item wrong, shorten its next gap. The closer your exam, the shorter the gaps — research suggests a gap of roughly 10–20% of the time left until the test.
What is spaced repetition?
Spaced repetition means revisiting material at increasing intervals instead of studying it all in one block. It's the practical form of the spacing effect, first described by Hermann Ebbinghaus in 1885 and confirmed by hundreds of experiments since. A large 2006 meta-analysis by Cepeda and colleagues found that spaced study reliably beats massed study for long-term retention.
Why does spacing work?
Memories fade along a forgetting curve: steeply at first, then more slowly. Each time you successfully retrieve something you've started to forget, the memory becomes more durable and the curve flattens. Reviewing too soon wastes effort (it's still easy); reviewing too late means relearning from scratch. Spacing aims for the sweet spot in between.
Spacing works best combined with active recall: the review should be a test, not a re-read. See active recall vs re-reading.
What is the best spaced repetition schedule?
| Review | When | What to do |
|---|---|---|
| 1st | Day 1 (next day) | Answer every question on the topic |
| 2nd | Day 3 | All questions; mark the ones you missed |
| 3rd | Day 7 | Mixed with other topics |
| 4th | Day 14 | Mixed; missed items get a short gap again |
| 5th | Day 30 | A quick check — then monthly until the exam |
The exact numbers matter less than the pattern: each gap longer than the last, and every review a test.
How do you adjust the schedule to your exam date?
Cepeda and colleagues (2008) found that the best gap between sessions grows with how long you need to remember something. Roughly: if the exam is 10 days away, review about every 1–2 days; if it's 2 months away, a gap of about a week works well. In practice:
- Exam in under 2 weeks: compress to days 1, 2, 4, 7.
- Exam in 1–2 months: the 1-3-7-14-30 schedule above.
- Material you need for years (medicine, languages): keep extending gaps — 2 months, 4 months.
What should you do when you get an item wrong?
Treat it as new again: look at the correct answer and its source, then bring the gap back down to a day. Items you keep missing usually need a different explanation, not more repetitions — rewrite the note or ask the question differently.
Do you need an app for spaced repetition?
No. A paper version works: keep topics in a list with the date of their next review, and each day test yourself on what's due. Software helps once you have hundreds of items. Whatever you use, the time-consuming part is having good questions to review. Ace turns your PDFs, slides and lecture videos into checked practice questions, and its study calendar lets you schedule 30, 45 or 60-minute sessions — solo or with a friend.
Frequently asked questions
What is the 1-3-7 rule for studying?
A simple spaced repetition pattern: review new material one day, three days and seven days after you first learn it, testing yourself each time. Extend with 14 and 30 days for longer-term retention.
Is spaced repetition better than cramming?
For anything you need beyond tomorrow, yes. Cramming can work for a test the next morning, but most of it is forgotten within days. Spaced study produces far better long-term retention.
How many times should you review something to remember it?
Usually four to six spaced, successful retrievals make a fact durable for months. Items you get wrong need extra rounds.
What is the forgetting curve?
Ebbinghaus's finding that memory declines quickly after learning and then more slowly. Each well-timed retrieval resets and flattens the curve.
Sources
- Ebbinghaus, H. (1885). Über das Gedächtnis [Memory: A contribution to experimental psychology].
- Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks. Psychological Bulletin, 132(3), 354–380.
- 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.
- Dunlosky, J., et al. (2013). Improving students' learning with effective learning techniques. Psychological Science in the Public Interest, 14(1), 4–58.
