Leitner System

What is the Leitner system?

The Leitner system is a flashcard learning method introduced by German science journalist Sebastian Leitner in his 1972 book "So lernt man lernen" ("How to learn to learn"). Cards are sorted into several boxes, and each box represents a review interval: box 1 is tested often, while boxes further back are reviewed less and less frequently.

How does it work?

New cards start in box 1. When you answer a card correctly, it moves one box back and is therefore reviewed less often. When you answer incorrectly, it returns to box 1 no matter which box it was in. Difficult material naturally accumulates in the front boxes and gets practised frequently, while well-known cards surface only rarely. Study time flows to where it does the most good.

Why is it so effective?

The system combines two of the best-evidenced learning principles: active recall (each card is a small self-test) and spaced repetition (increasing intervals). These two techniques — practice testing and distributed practice — were rated by Dunlosky and colleagues (2013) as the most effective of ten study methods they reviewed. The Leitner system puts both into practice with nothing more than paper cards and a box.

How do you set it up?

You need a box with three to five compartments and a simple schedule, for example: box 1 daily, box 2 every two days, box 3 every four days. The key is honest self-testing — answer first, then flip the card and check. A few cards a day are enough to start with; regularity matters more than volume. One limit of the paper version is that its intervals are equally fixed for every card — modern flashcard apps with a spaced-repetition algorithm are digital descendants of the same idea and adjust the spacing for each card individually. You'll find a step-by-step guide in the article The Leitner system explained.

The Leitner system is especially suited to vocabulary, technical terms and factual knowledge that needs to stay retrievable over time.