The Leitner System: How to Remember Everything

Empty moleskine notebook on a table in a café.
© Robert Moszczynski

The Leitner system uses flashcards and spaced repetition, helping you to study new information. By using time intervals, you will be able to retain information longer.

There are no bad students, no stupid people; there are only miserable learning methods.

— Sebastian Leitner

When we learn, we want to retain as much as possible with the least amount of work. To achieve this, we need a good memory. Thanks to the Leitner system, we can significantly increase our learning success.

Learning facts is not only essential for the humanities, such as linguistics.

Facts are also the foundation of knowledge in the natural sciences, where concepts are paramount. We can understand and apply concepts but cannot retain them permanently if we forget the basic facts.

A good memory is a prerequisite for success in many areas of life. It is, therefore, worthwhile to improve it to learn effectively.

Sebastian Leitner was a German publicist. In his book “So lernt man lernen. Der Weg zum Erfolg.” he proposed a system that is easy to use and requires only pen and paper, and promises an enormous increase in learning success.

Why Do We Forget

I remember the things I want to forget and forget those I don’t want to forget.

— Euripides

Forgetting is often perceived as a malfunction of the brain. It feels like a flaw, creates dissatisfaction and frustration. Yet, it is a fundamental part of how the brain works.

We forget to separate the essential things from the unimportant.

Every day, the brain has to absorb a lot of information. There are not only positive and helpful facts but also negative and unimportant ones. We overwrite the non-essential information to make room for new ones.

Forgetting helps to protect the brain from overload. Only some information is stored in the long-term memory and remains permanently available.

As important and helpful forgetting can be for the proper functioning of the brain, we wish to retain as much learning material as possible in learning.

Graphical representation of the forgetting curve according to Hermann Ebbinghaus.
Graphical representation of the forgetting curve according to Hermann Ebbinghaus. (The original uploader was Icez at English Wikipedia., Public domain, via Wikimedia Commons

The forgetting curve shows how we forget new information over time. It does not remain in short-term memory for long.

When we repeat it, we signal to the brain that the information is important and worth keeping. After the brain has classified the information as important, it moves it further into long-term memory with each repetition, where it is permanently stored.

Spaced Repetition and Long-Term Memory

Our goal is to learn so that as much learning material as possible is stored in long-term memory. This requires repetition of the learning material.

We can achieve the best results if we increase the time intervals between repetitions. This principle is called spaced repetition and is the basis of the Leitner system.

To follow spaced repetition, we need a schedule. This is a schedule that tells us when to repeat what we have to repeat.

Storing Knowledge

You can’t think without writing; at least not in a sophisticated, connectable way.

— Niklas Luhmann (German sociologist and inventor of the Zettelkasten)

Before we discuss the schedule in detail, we want to clarify how we can capture the learning material.

The original Leitner system is based on physical index cards that are written on both sides. One side contains the question and the other the answer.

The biggest advantage of physical index cards is their simplicity. You can write on them as you like. It is also possible to adjust the schedule at any time. There is no stiff software in between.

Index cards in size 4.1″x5.8″ (DIN A6) have proven to be particularly universal. The size of 2.9″x4.1″ (DIN A7) is also well suited for learning vocabulary.

Alternatively, there are also software solutions such as Anki (

Leitner’s Schedule and a Flashcard Box

To keep the temporal intervals of the learned information, we can follow a schedule. A time sequence of repetitions helps us to repeat the right information at the right time.

Leitner has proposed a schedule in which the time intervals are increased to achieve an optimal learning effect.

Leitner’s schedule for a 64-day learning period.
Leitner’s schedule for a 64-day learning period.

The procedure is as follows:

A piece of information is written on an index card. The card can be in one of seven slots in the flashcard box. The slots represent the path from short-term to long-term memory. Slot 1 contains new cards that still need to be learned to move to the next slots, and slot 7 contains cards that are almost learned.

When we learn cards from a slot, we proceed as follows. We read the question on the card and try to answer it. Then the answer was correct; we put the card in the next slot, e.g. from slot 1 to slot 2. If we were wrong, we would put it back to slot 1, e.g. from slot 5 to 1.

Leitners Schedule Card Movement
Correctly answered questions are moved to the next slot and incorrectly answered questions are moved to the first slot. (Zirguezi, CC0, via Wikimedia Commons

The schedule is organised into 64 days. All new cards go into slot 1. All correctly answered cards from slot 7 are considered learned and can be archived.

For example, on day 13, we learn the cards from slots 1, 2 and 4.

Intensify Learning With Active Recall

Creative people are better at recognizing relationships, making associations and connections, and seeing things in an original way–seeing things that others cannot see.

— Nancy Andreasen

Repeating facts using a schedule is a proven and effective way to store them in long-term memory. However, we should not use it to memorise isolated, useless facts.

The question is, how do we learn the material on the card? What we definitely shouldn’t do is repeated reading or multiple copying. This is a waste of time and discourages learning.

Understanding and associations are the keys to a good memory.

Our brain works associatively. This means that it forms links between information units and stores them in a structure. Only when this structure exists is the brain able to store the information in long-term memory permanently.

So the crucial thing is to answer the question on the card to evoke as many associations as possible.

  • What similar facts do I already know?
  • Can I question the answer?
  • What would happen if you saw it from a different perspective?

It is all about actively working with the material.

The application of knowledge is the transition from passive to active learning. With practice, we immediately see what we have got wrong and can close the gaps in our knowledge.

Tell me and I forget. Teach me and I remember. Let me do it and I learn.

— Benjamin Franklin

The ultimate form of active recall is to teach others. When you explain something to others, you should do it in a way that is very easy to understand. That means being able to reduce the information to the absolute core. Only if we can do this, we have understood it right.

The person who says he knows what he thinks but cannot express it usually does not know what he thinks.

— Mortimer Adler

A great master of active recall was Richard Feynman, a US physicist and Nobel laureate.

His method consists of 4 steps:

  1. Explain the topic as simple as possible
  2. Write down the missing knowledge
  3. Fill in the gaps in your knowledge
  4. Repeat

Use Mnemonics Where Associations Are Not Possible

It is not always possible to develop sufficiently good associations. Lists or dates are complicated to remember.

You can use mnemonics to memorize unrelated information. The loci method can help you learn lists.

For example, you imagine a familiar room. There are things there that you can clearly remember. Now you turn clockwise in your mind and associate a piece of information with the objects in the room.

This visual technique allows you to remember unrelated lists, for example, a long speech that you can give without looking at a piece of paper.

Sleep After Learning

Scientists proved that you should take a nap after studying.

Sleep plays a key role in the consolidation of new knowledge and additionally regenerates the mind and body.

However, it should not last longer than 15–20 minutes. A longer sleep reduces the refreshing effect and leads to sluggishness. Set an alarm clock if you need to.

Divide Up and Stay Tuned

Divide et impera (lat. divide and conquer)

Sometimes the goal seems far away. The amount of learning can be intimidating. It isn’t easy to get started.

Try to break a big task into small parts you can manage and measure.

With enough perseverance and a systematic approach, you can divide the material into small portions and learn every day only a piece at a time.

If you have realistic goals, you stay motivated and don’t have to fear that you won’t complete the task before the deadline.

Learning is like rowing against the current. As soon as you stop, you drift back.

— Laotse

You have to stick to a plan. Anything else will cause stress and bulimia learning. That is neither effective nor really fun.

Studying is not a sprint. It’s a marathon. Watch out for your speed and energy management.

Focus Is Key

He who undertakes much, accomplishes little.

— German proverb

We can use the best learning methods, but if we cannot focus, we will ultimately fail.

We live in a world driven by distractions. At the forefront are smartphones, which by design are distracting and highly addictive.

The use of smartphones reduces our concentration span. We are not able to concentrate on a task for longer. Our intelligence quotient measurably decreases when a smartphone is just lying on the table.

Learning consumes the brain a lot of energy. It takes time to reach the state of flow where you lose the sense of time passed and thing on a highly abstract level. It can take up to 30 minutes to get there. In this state, it is easier to concentrate and work effectively. If we are constantly interrupted, we are ripped out of the flow and have to start over and over again.

We must create an environment in which we are not constantly interrupted. Turn off your mobile phone and find a suitable place, e.g. the library or an exercise room, if you cannot find it at home.

Have Fun and Enjoy

Once we have mastered the methods and freed ourselves from distractions, we can start our learning adventure.

When you lose track of time, and everything suddenly seems easy and funny, you have reached the optimal state.

Stay there as long as you can and success will come on its own!