Skip to content
Glossary

What Is the Leitner System? The Original Spaced Repetition

May 28, 20263 minEmily Chen
Share:XLinkedIn
In this article
  1. 1.How it works
  2. 2.Why it works
  3. 3.When to use Leitner today
  4. 4.Leitner vs modern algorithms
  5. 5.Related reading

Short answer. The Leitner system is a flashcard organization method invented by German journalist Sebastian Leitner in 1972, using three to five physical boxes to schedule reviews at growing intervals. It's the original implementation of [spaced repetition](/blog/what-is-the-spacing-effect) and the conceptual ancestor of modern algorithms like [FSRS](/blog/what-is-fsrs).

How it works

You have several boxes (usually 5):

  • Box 1: review daily
  • Box 2: review every 2 days
  • Box 3: review every 4 days
  • Box 4: review weekly
  • Box 5: review monthly

    • When you create a new card, it starts in Box 1. When you review a card:

  • Got it right? Move to the next box (longer interval)
  • Got it wrong? Move back to Box 1 (review tomorrow)

    • Over time, the cards you find easy migrate to higher boxes (less frequent review); cards you struggle with stay in Box 1.

    Why it works

    The Leitner system implements two cognitive-science findings without needing any technology:

  • Spacing effect — cards review at growing intervals
  • Retrieval practice — every review is an active recall attempt

    • When to use Leitner today

    Most students should use modern algorithmic spaced repetition tools (FSRS-based: Anki, SimpleQuizMaker review queue). But Leitner still has uses:

  • Pure paper study — no screens, no software
  • Teaching the concept — Leitner is visually obvious in a way algorithms aren't
  • Backup when offline — works without electricity
  • Beginner introduction to spaced repetition — proves the principle before committing to apps

    • Leitner vs modern algorithms

    Modern algorithms (FSRS, SM-2) improve on Leitner in two ways:

  • Tunable intervals per card — FSRS adjusts based on each card's actual difficulty
  • Probabilistic scheduling — based on predicted retrievability, not fixed boxes

    • For most studiers, the modern algorithm is meaningfully better. But Leitner is still strictly better than no spaced repetition at all.

    Related reading

  • [Spaced Repetition Guide](/blog/spaced-repetition-guide)
  • [Spaced Repetition vs Flashcards](/blog/spaced-repetition-vs-flashcards)
  • [What Is FSRS?](/blog/what-is-fsrs)
  • [What Is the Spacing Effect?](/blog/what-is-the-spacing-effect)

    • Try modern algorithmic spaced repetition with a free quiz.

    Get weekly study & quiz tips

    Join teachers and students who get practical tips on quizzing, active recall, and AI-powered learning.

    Share:XLinkedIn

    Emily Chen

    Cognitive Psychology Writer & Study Skills Coach

    Practice with AI-generated quizzes

    🔬 Science Quiz Generator

    Ready to create your first quiz?

    Use AI to generate quizzes from your own study materials in seconds.

    Try SimpleQuizMaker Free

    Related Articles

    Glossary

    What Is FSRS? The Modern Spaced Repetition Algorithm Explained

    4 min

    Glossary

    What Is the Testing Effect? The Research Behind Active Recall

    4 min

    Glossary

    What Is the Spacing Effect? Why Spread-Out Study Beats Cramming

    4 min

    Back to Blog