What Is the Leitner System?

The Leitner system is a simple way to do spaced repetition with paper flashcards and a set of boxes. Every card starts in box 1. When you answer a card correctly, it moves up a box; boxes higher up are reviewed less often. When you get a card wrong, it goes back to box 1. Words you know drift into rarely reviewed boxes, and words you struggle with stay in front of you.

Origin

Sebastian Leitner, a German science journalist, introduced the method in his 1972 book So lernt man lernen ("How to learn to learn"). His original box (in German, a Lernkartei) had five compartments of increasing size, so a compartment had to fill up before its cards were reviewed. The idea turned the spacing effect into a practical routine long before apps existed, and it inspired many later flashcard programs.

How it works: a sample schedule

Modern versions usually tie each box to a review frequency. A common five-box schedule:

Doubling the interval at each step creates the expanding gaps that make spaced repetition efficient.

A vocabulary example

Why it matters for learning words

The Leitner system combines two of the best-supported learning strategies: active recall (you must answer before turning the card) and spacing (intervals grow as you succeed). It also solves the main practical problem of flashcards: deciding what to review today. Without a system, learners tend to review the cards they already know because it feels good.

It is transparent, needs no software and works offline, which is why teachers still use it in classrooms.

Leitner vs algorithmic schedulers

The main weakness of Leitner is coarseness: every card in a box shares the same interval, and a single mistake on a well-known card sends it all the way back to the start. Algorithms adapt each card individually and usually need fewer reviews for large decks.

How to run your own Leitner box

1. Get five envelopes, boxes or labeled sections of a deck.
2. Write the word on the front; the meaning and an example sentence on the back.
3. Add a limited number of new cards per day, for example 10.
4. Each day, review box 1 plus whichever boxes are due.
5. Answer aloud before flipping. Move cards up or back strictly.

The spaced repetition scheduler can generate dates if you prefer a calendar to boxes. Wordie's recall mode uses a similar Forgot / Hard / Easy rating to update a mastery score, though it is not a Leitner box or a full scheduler.

Common mistakes

• Overfilling box 1. Too many new cards make daily review a chore.
• Being lenient. "Almost right" is wrong; otherwise weak cards climb too fast.
• Skipping days. The schedule assumes regular reviews.

Sources: Leitner, S. (1972). So lernt man lernen. Freiburg: Herder.