Spaced repetition
Review what you are about to forget, and skip what you already know. The Leitner system does this with nothing more than a few boxes of index cards. Run it below, one card at a time.
Day 1
12 cards due today · 0 reviews so far
Box 1every 1 day
Box 2every 2 days
Box 3every 4 days
Box 4every 8 days
Box 5every 16 days
Card 1 is up. Did you remember it?
Why spacing works
Right after learning, memory drops quickly; this is the forgetting curve. A review that makes you work to recall something slows the next drop, so you can wait longer before the one after. Reviewing too soon wastes effort because the answer is still fresh; too late and you are relearning from scratch. Spaced repetition aims for the point in between.
In a review of ten learning techniques, Dunlosky and colleagues (2013) rated "distributed practice" as one of only two with high utility, the other being practice testing. Spaced repetition with flashcards combines both.
A schedule you can use without an app
| Review | When | What to do |
|---|---|---|
| 1 | Same day or next morning | Recall the lecture from memory, fill gaps from notes |
| 2 | 3 days later | Flashcards or a short self-test |
| 3 | 1 week later | Practice questions mixing this topic with others |
| 4 | 2 weeks later | Full practice test |
| 5 | A month later / before the exam | Only what you missed in review 4 |
How to memorise fast (without cramming)
- Make the card small. One fact per card; big cards fail as a whole.
- Say it before you flip. Recognising the answer is not recalling it.
- Be honest when grading. Moving a half-known card up only means you meet it again when you have forgotten it.
- Sleep between sessions. Memory consolidation during sleep is one reason a gap helps.
The flashcard maker on this site runs exactly this five-box schedule on the cards you make from your notes, and remembers each card’s box in your browser.
Questions students ask
What is spaced repetition?
Spaced repetition means reviewing material at increasing intervals: soon after learning, then after a few days, then after weeks. Each successful review slows forgetting, so the next review can wait longer. It is the practical application of the spacing effect first described by Hermann Ebbinghaus in 1885.
How does the Leitner system work?
Sebastian Leitner described it in his 1972 book "So lernt man lernen". Flashcards sit in numbered boxes. All new cards start in box 1. A correct answer moves a card up one box; a wrong answer sends it back to box 1. Box 1 is reviewed every session and higher boxes less and less often, commonly every 1, 2, 4, 8 and 16 days.
What is the best spaced repetition schedule?
There is no single best schedule. A common starting point is 1, 3, 7, 14 and 30 days. Cepeda et al. (2008) found the ideal gap depends on how long you need to remember: roughly 10 to 20% of the time until the test. Apps such as Anki adjust intervals per card based on how easily you answer.
How do I memorise something fast?
For the long term, fast memorisation is really efficient memorisation: learn it once properly, test yourself rather than reread, and review just as you are about to forget. Short, spaced self-tests beat one long session with the same total time.