The Leitner System: How Five Boxes Schedule Your Reviews
The Leitner system schedules flashcard reviews with a row of numbered boxes. After reading this guide you will be able to set one up with paper cards, follow a card through two weeks of reviews, and explain the 1, 2, 4, 8 and 16 day waits used in Practice. If spaced reviews are new to you, start with what spaced repetition is.
Two honest notes first. The method is known as the Leitner system. The German National Library catalog lists So lernt man lernen, a German-language book by Sebastian Leitner, published by Herder in 1972. We have seen only that catalog entry, not the book, so this article does not describe or quote it, and we do not claim where the box method began. And the day numbers below are a simple model of our own, inspired by the Leitner system. We do not attribute them to his book, and they are not a law of memory.
The rest of this guide is locked
Play a round of five cards to open it and collect this guide’s stamp. Or read it now without playing, and skip the stamp.
The round uses cards from the The Leitner Box Model deck. Your stamps and progress stay in this browser.
How a box system works
A box is a pile or container of cards that share a review rhythm. The box a card sits in tells you how long to wait before you see it again. Low boxes come up often, and high boxes come up rarely.
- Answer a card correctly and it moves to a box with a longer wait.
- Miss a card and it goes back to the first box, so it returns soon.
- Cards you know well drift into high boxes and take little of your time.
You can run this with five envelopes or with a column in a spreadsheet. On paper, write the next due date in pencil on each card.
The Practice model: 1, 2, 4, 8 and 16 days
Practice uses five boxes with waits of 1, 2, 4, 8 and 16 days. A new card answered right goes to box 2, and a new card answered wrong goes to box 1. After that, a right answer moves a card up one box and a miss sends it back to box 1. Mastered means a right answer while the card is already in box 5.
| Box | Wait before the next review | After a right answer | After a miss |
|---|---|---|---|
| Box 1 | 1 day | Moves to box 2 | Stays in box 1 |
| Box 2 | 2 days | Moves to box 3 | Back to box 1 |
| Box 3 | 4 days | Moves to box 4 | Back to box 1 |
| Box 4 | 8 days | Moves to box 5 | Back to box 1 |
| Box 5 | 16 days | Counts as mastered, stays in box 5 | Back to box 1 |
The waits grow so that cards you keep answering correctly come up less often, and each wait doubles. That is a design choice, not a schedule shown to be optimal. A meta-analysis of 29 studies found a strong benefit of spaced retrieval practice over massed, but no significant difference between expanding and uniform schedules. Its authors say the results do not support the widely held belief that intervals should progressively increase (Latimier et al., 2021). Growing waits were not shown to be better than even ones.
A two-week worked example with three cards
Say you add three cards on day 0: A, B and C. Assume you review each card on the day it comes due.
| Day | Cards due | Your answers | Where the cards go |
|---|---|---|---|
| 0 | A, B, C (all new) | A right, B right, C wrong | A and B to box 2, C to box 1 |
| 1 | C | C right | C to box 2 |
| 2 | A, B | A right, B wrong | A to box 3, B to box 1 |
| 3 | B, C | Both right | B to box 2, C to box 3 |
| 5 | B | B right | B to box 3 |
| 6 | A | A right | A to box 4 |
| 7 | C | C right | C to box 4 |
Look ahead to day 14. Card A, which you never missed, appeared on days 0, 2, 6 and 14, so four sessions in two weeks. Card B, which you missed once, appeared on days 0, 2, 3, 5 and 9. The box system spends more of your time on the cards that trip you up.
Limits and how to adapt the boxes
- The waits are a model. A 16-day wait does not suit a test next week. The best gap between sessions tended to grow with the time until the final test (Cepeda et al., 2006), so shorten or skip the high boxes when your test is close. See how long to wait between reviews. That adjustment is our practical advice, not a tested rule.
- Recall adds to spacing. Kang (2016) reports that incorporating tests into spaced practice amplifies the benefits, so answer from memory before you flip a card.
- Boxes pile up work. Every new card creates future reviews. How many new cards per day shows how a daily batch grows under this model.
- Vague cards are hard to grade in any box. Keep each card to one idea, as described in how to write flashcards that work.
You can try the five-box model in Practice. The tool is free, has no accounts, and keeps its data in your browser.
Common mistakes
- Moving a card up after a lucky guess or a peek. Mark a card right only if you answered before flipping it. A generous mark pushes the card into a longer wait than it earned.
- Reviewing every box every day. Review only the cards whose wait is over. Passing through the whole deck daily removes the spacing.
- Treating 1, 2, 4, 8 and 16 as a law. It is a simple model inspired by the Leitner system. Change the waits to fit your test date and your own results.
- Writing cards that hold several facts. A half-right card is hard to grade. Split it into separate cards, one idea each.
Frequently asked questions
Who invented the Leitner system?
The sources we checked do not settle who invented the box method, and we do not claim a history. The method is known as the Leitner system, and the German National Library catalog lists a 1972 German-language book by Sebastian Leitner, So lernt man lernen. We have not read it, so we cannot say how closely a modern box setup follows it. Practice uses a simple model inspired by the system.
Do I have to use 1, 2, 4, 8 and 16 days?
No. Those are the waits in Practice. One meta-analysis found no significant difference between expanding and uniform schedules (Latimier et al., 2021), so a rhythm you can keep is a reasonable choice.
How many boxes do I need?
None of the sources we read compares numbers of boxes. Five boxes with growing waits is a convenient size for a few weeks of study, which is practical advice, not a finding. Use fewer boxes, or shorter waits, if your test is close.
What happens when I miss a card in a high box?
In Practice it goes back to box 1 and returns after one day, and then you work it up again. That is a design choice, and results vary between people.
Sources
We opened each source below before citing it. See Methodology and Sources for how we check them.
- Latimier, A., Peyre, H., & Ramus, F. (2021). A Meta-Analytic Review of the Benefit of Spacing out Retrieval Practice Episodes on Retention. Educational Psychology Review, 33(3), 959-987. Open the source
- 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. Open the source
- Kang, S. H. K. (2016). Spaced Repetition Promotes Efficient and Effective Learning. Policy Insights from the Behavioral and Brain Sciences, 3(1), 12-19. Open the source
This guide is general study help, not medical or professional advice. It was last reviewed on November 12, 2026. Spot a mistake? Tell us here.