Leitner System vs Anki: Which Flashcard Method Wins?

Two titans of spaced repetition. One born in 1972 from a German journalist's shoebox. The other coded in 2006 by a Japanese med student. Both promise to beat the forgetting curve — but they take radically different paths to get there. Here's an honest breakdown of the Leitner system and Anki, and how to pick the right one for you.

Introduction: two philosophies of memory

Every flashcard app makes the same core promise: show you the right card at the right time. The difference is how they decide what "the right time" means.

The Leitner system uses a structural approach. Cards live in numbered boxes. Each box has a fixed review interval. Get the card right, it moves up. Get it wrong, it drops back to Box 1. The intervals are predetermined — every card in Box 4 gets reviewed on the same schedule, regardless of whether it's an easy vocabulary word or a brutal organic chemistry mechanism.

Anki takes an algorithmic approach. Every card has its own computed interval, based on how many times you've reviewed it, how hard you rated it, and a mathematical model of human forgetting. No two cards share the same schedule unless by coincidence.

Both methods are grounded in the same cognitive science: Hermann Ebbinghaus's forgetting curve, active recall, and the spacing effect. The disagreement is about how much optimization a human learner actually needs — and what that optimization costs in complexity.

How the Leitner system works

Sebastian Leitner's method is elegant in its simplicity. You have a series of boxes (traditionally 5, modernized to 7 in most implementations). All new cards enter Box 1, which you review daily. When you answer a card correctly, it advances to the next box. When you answer incorrectly, it returns to Box 1 — no matter how far it had progressed.

Each box has a progressively longer review interval: daily, then every 2 days, then every 4, 7, 15, 31, and finally 64 days. A card that passes all seven reviews without a mistake graduates in about 119 days — roughly four months of spaced recalls that match the forgetting curve's natural decay.

The beauty of this system is transparency. At any moment, you know exactly where every card stands. Box 3 means "I've recalled this correctly three times at increasing intervals." There's no hidden state, no ease factor, no mathematical model running behind the scenes. The schedule is deterministic and human-readable.

The Leitner insight: you don't need a perfect schedule. You need a good-enough schedule that you'll actually follow. Simplicity drives consistency, and consistency drives retention.

How Anki works: from SM-2 to FSRS

Anki was created in 2006 by Damien Elmes, a medical student who wanted to optimize his study sessions. Its original scheduling engine was based on SM-2, an algorithm developed by Piotr Wozniak in 1987 for the SuperMemo project. SM-2 assigns each card an "ease factor" (a multiplier that adjusts how quickly intervals grow) and recalculates it after every review based on your self-reported difficulty rating.

In 2023, Anki adopted a new default algorithm: FSRS (Free Spaced Repetition Scheduler), developed by Jarrett Ye. FSRS is trained on over 700 million review logs and uses a four-parameter memory model to predict each card's probability of recall at any given moment. It adjusts for card difficulty, current stability (how well you know it), and the "desired retention" rate you set (typically 90%).

The result is per-card precision. A card you find easy might jump to a 45-day interval after just three reviews. A card you struggle with might stay at 3-day intervals for weeks. FSRS continuously updates its model as you study, learning your patterns over time.

The tradeoff is complexity. Anki has over 50 settings that affect scheduling. Terms like "ease factor," "graduating interval," "new card steps," "learning steps," and "maximum interval" require genuine study to understand. The FSRS optimizer requires collecting review data and running a parameter tuning process. Many Anki users never configure these settings correctly — and suboptimal settings can undermine the very precision the algorithm promises.

Head-to-head comparison

Let's compare the two methods across the dimensions that actually matter to learners. Neither system is universally better — each has clear strengths.

When to choose the Leitner system

The Leitner method is the right choice when simplicity and consistency matter more than algorithmic precision. That's most people, most of the time. Specifically:

• You're new to flashcards. Starting with Leitner builds the habit of daily review without the cognitive overhead of learning a complex app. Once the habit is solid, you can decide if you need more.
• You study languages at a normal pace. For typical language learning (1,000–3,000 words over several months), the Leitner system's fixed intervals are more than sufficient. The marginal gain from per-card scheduling is negligible at this scale.
• You value understanding your system. With Leitner, you always know where you stand. There's no "why did the algorithm show me this?" frustration. This transparency builds trust, and trust keeps you coming back.
• You want a free, low-friction tool. LeitnerBox gives you the full 7-box system with unlimited cards, achievements, and practice mode — free, with no account required. The $7.99 lifetime Pro tier adds cloud sync and analytics. No subscription, no recurring cost.
• You study on iPhone. Anki's iOS app costs $24.99. LeitnerBox is free. For budget-conscious students, this is a real consideration.

When to choose Anki

Anki earns its reputation among power users for good reasons. It's the right tool when the scale or nature of your material demands precision:

• Medical school. Med students routinely study 20,000–40,000 cards. At this scale, per-card scheduling saves hours per week by showing only the cards that truly need review. Shared decks like AnKing provide pre-tagged, pre-formatted content for every board exam topic.
• You need multimedia cards. If your material involves audio pronunciation, chemical structures, anatomical diagrams, or mathematical notation, Anki's template system and multimedia support are unmatched.
• You enjoy tinkering. Some people genuinely enjoy optimizing their workflow. If you find satisfaction in configuring FSRS parameters, creating custom card templates with CSS, and analyzing your review statistics, Anki is a playground.
• You already use Anki successfully. The best system is the one you already use. If Anki is working for you, there's no reason to switch. Anki is a proven tool with a 20-year track record.

That said, it's worth noting that many Anki users never unlock the tool's full potential. Studies of Anki usage patterns suggest that a significant portion of users stick with default settings — and the defaults are not always optimal. FSRS only works well when trained on sufficient review data (at least 1,000 reviews), which means new users are essentially running on an untrained model.

Our take

We built LeitnerBox because we believe the original Leitner system is underrated. In a world obsessed with algorithmic optimization, there's something radical about a method that's fully transparent, requires zero configuration, and has worked reliably for over 50 years.

Anki is a powerful tool. We respect it. For extreme-scale use cases like medical school, it's hard to beat. But for the vast majority of learners — language students, exam preppers, professionals upskilling, hobbyists memorizing poetry or history — the Leitner system delivers 95% of the benefit with 10% of the complexity.

The research backs this up. A 2019 meta-analysis in Psychological Bulletin found that the specific spacing schedule matters far less than the act of spacing itself. Whether you review a card at day 7 or day 9 has a trivial impact on retention. What matters is that you show up and review at all. And simple systems make showing up easy.

The best flashcard system is the one you use every day. For most people, that's the simplest one available. The Leitner system has survived five decades not because it's mathematically optimal, but because it's humanly optimal. It fits in your head, it works without Wi-Fi, and it never asks you to calibrate an ease factor.

If you've been intimidated by Anki's learning curve, or if you tried it and bounced off the settings screen — give the Leitner system a chance. You might find that less algorithm means more learning.