How Spaced Repetition Works (And Why It's the Best Way to Study)

What if there was a study technique so effective that it could help you remember almost anything — permanently? There is. It's called spaced repetition, and decades of cognitive science research prove it works.

In this guide, we'll explain exactly how spaced repetition works, why it's so powerful, and how you can start using it today.

The Forgetting Curve: Why We Forget

In 1885, German psychologist Hermann Ebbinghaus discovered the "forgetting curve" — a mathematical model showing how memories decay over time. Without review, you forget approximately:

• 50% of new information within one hour
• 70% within 24 hours
• 90% within a week

This is why cramming doesn't work. You might remember enough for tomorrow's exam, but the knowledge evaporates within days.

How Spaced Repetition Fights Forgetting

Spaced repetition is elegantly simple: review information at increasing intervals, timed to catch memories just before they fade. Each successful review strengthens the memory and extends the time before you need to review again.

Here's what a typical schedule looks like:

• First review: 1 day after learning
• Second review: 3 days later
• Third review: 7 days later
• Fourth review: 21 days later
• Fifth review: 60+ days later

Eventually, you might only need to review something once or twice a year to maintain it permanently. This is far more efficient than reviewing everything daily.

The SM-2 Algorithm

The most widely used spaced repetition algorithm is SM-2, developed by Piotr Wozniak in the late 1980s. Tools like DeckStudy and Anki use this algorithm to calculate optimal review intervals.

After each review, you rate how well you remembered:

• Easy: Interval increases significantly (e.g., 1 day → 4 days)
• Good: Interval increases normally (e.g., 1 day → 3 days)
• Hard: Interval stays the same or increases slightly
• Again: Card resets to a short interval

The algorithm adapts to your performance on each individual card, creating a personalized review schedule.

Why Spaced Repetition Is So Effective

1. The Testing Effect

Simply trying to recall information strengthens memory more than re-reading it. Every time you see a flashcard and attempt to answer, you're actively testing yourself — which is proven to be one of the best learning strategies.

2. Desirable Difficulty

Reviewing right before you forget creates a "desirable difficulty" — the slight struggle of recall strengthens the memory trace. If review is too easy (too soon), you don't learn much. If it's too hard (too late), you've already forgotten.

3. Interleaving

Spaced repetition naturally interleaves different topics, which research shows improves learning compared to studying one topic at a time.

How to Start Using Spaced Repetition

The easiest way to start is with a flashcard app that has spaced repetition built in. DeckStudy makes it incredibly simple:

1. Paste your study material
2. AI generates flashcards automatically
3. Study daily — the algorithm shows you exactly which cards to review
4. Rate your recall after each card
5. Watch your knowledge compound over time

The key is consistency. Even 10-15 minutes of daily review is more effective than hours of cramming once a week.

Common Mistakes with Spaced Repetition

• Adding too many cards at once: Start with 10-20 new cards per day. More than that creates an overwhelming review pile.
• Skipping days: Missed reviews compound. Try to review every day, even if it's just for 5 minutes.
• Bad card design: Cards should test one concept each. AI-generated cards from tools like DeckStudy typically follow this principle automatically.
• Not trusting the algorithm: If the algorithm says to review in 3 days, trust it. Don't review early "just to be safe."

Frequently Asked Questions

How long until I see results with spaced repetition?

Most students notice improved retention within 1-2 weeks. After a month of consistent use, the difference is dramatic — you'll remember things you would have completely forgotten without spaced repetition.

Does spaced repetition work for all subjects?

Spaced repetition is most effective for factual knowledge — vocabulary, definitions, formulas, historical dates, medical terms, etc. It's less suited for skills that require practice (like math problem-solving or essay writing), though it can help with the foundational knowledge those skills require.

How much time should I spend on spaced repetition daily?

15-30 minutes per day is the sweet spot for most students. This is enough to review due cards and add a reasonable number of new cards without burning out.

Start Building Lasting Memories

Spaced repetition isn't a hack or a shortcut — it's how your brain is designed to learn. By reviewing at scientifically optimal intervals, you work with your memory instead of against it.

Try DeckStudy free and let spaced repetition transform the way you study. Your future self will thank you.