The Leitner System: How the Flashcard Box Method Works

Long before flashcard apps, there was a shoebox. In 1972 the German science journalist Sebastian Leitner described a way of studying flashcards with a divided box that makes you review the cards you struggle with often and the cards you know rarely. It's simple enough to set up in ten minutes with index cards, and it's the direct ancestor of every spaced-repetition app. Here's how it works, a schedule you can copy, and when it's worth switching to software.

The idea in one sentence

Cards you answer correctly move up a box and come back less often; cards you get wrong go back down and come back often. Over time, your effort concentrates automatically on the cards you don't know yet.

Where it came from

Leitner set out the method in his 1972 book So lernt man lernen ("How to learn to learn"). His original learning box had five compartments of increasing size — 1, 2, 5, 8 and 14 centimetres deep. Cards moved forward through the compartments as you learned them, and you reviewed a compartment when it filled up, so the bigger compartments naturally came round less often. Today most people use a simpler version with fixed review days for each box.

How to set it up

1. Get five boxes — envelopes, sections of a card box, or piles held with rubber bands. Label them 1 to 5.
2. Put every new card in Box 1.
3. Review boxes on a schedule (see below). Box 1 comes up most often, Box 5 least often.
4. When you review a card: if you get it right, move it up one box. If you get it wrong, send it back to Box 1.
5. Cards that pass Box 5 are "retired" — you know them well. Review retired cards occasionally before an exam.

A schedule you can copy

A common five-box schedule:

In practice: every day, do Box 1. On even days, add Box 2. Every fourth day, add Box 3, and so on. A simple way to keep track is a calendar with the boxes you owe written on each day.

The exact numbers matter less than the principle — each box waits longer than the one before. That widening gap is spaced repetition, the same idea modern algorithms use.

Strict or gentle?

There are two common rules for a wrong answer:

• Strict (Leitner's original): a missed card goes all the way back to Box 1. Best for material you must know perfectly.
• Gentle: a missed card drops back just one box. Less discouraging for large decks, and a card you nearly knew doesn't have to start over.

Pick one and stick with it. If Box 1 keeps overflowing, switch to gentle — or add fewer new cards a day.

What the Leitner system gets right

• It's active recall. You answer before you check — the technique research rates among the most effective there is (active recall vs re-reading).
• It spaces your reviews. Known cards come back at widening gaps, which is how memories become durable (the spacing effect).
• It puts effort where it's needed. Hard cards get lots of practice; easy ones stop wasting your time.
• It needs nothing but paper. No phone, no distractions, and writing the cards is itself a bit of learning.

Where it struggles

• The gaps are the same for every card. Every card in Box 3 waits four days, whether it's easy or hard for you. Modern algorithms time each card individually.
• The gaps stop growing. Sixteen days is the longest wait in the schedule above. For an exam a year away, you want gaps of months; a five-box system either keeps showing you cards you know or retires them too early.
• Missed days snowball. Skip three days and several boxes are due at once, with no easy way to prioritise.
• It doesn't scale. A few hundred cards are manageable. A few thousand — a typical full exam syllabus — means a lot of shuffling and bookkeeping.

Leitner box vs spaced-repetition apps

Modern schedulers are, in effect, a Leitner box with a separate box for every card. SM-2 multiplies each card's gap by an ease factor; FSRS predicts when you will forget that card and schedules the review just before. Same principle, much finer control.

Which should you use?

• A few hundred cards, a short course, or you study better on paper? A Leitner box is excellent — and free.
• A whole exam syllabus, months of preparation, or you keep missing days? Use an app, and let the algorithm keep the timetable.

Plenty of students do both: a Leitner box for one tricky topic, an app for everything else.

Do this in StudyTab

StudyTab is the Leitner idea with the bookkeeping removed: every card gets its own schedule from FSRS, gaps keep growing for as long as you keep remembering, and a missed day doesn’t scramble a set of boxes. You can make cards from your notes, a PDF or a photo of your handwritten notes instead of writing each one out.

Bottom line

The Leitner system is spaced repetition in its simplest form: right answers move up and come back later, wrong answers go back and come back sooner. It's a brilliant way to start and works well for a few hundred cards. When your deck grows or your exam is months away, a spaced-repetition app does the same job per card, with gaps that keep growing.

Want the Leitner method without the boxes? Build a deck free.