What Is Spaced Repetition?
Spaced repetition is a study technique where you review material at increasing intervals over time. Instead of cramming everything the night before, you spread your reviews across days, weeks, and months.
The result? You remember 90%+ of what you study instead of the typical 20% from cramming.
The Forgetting Curve
In 1885, German psychologist Hermann Ebbinghaus discovered the forgetting curve — the rate at which we forget new information:
- After 1 hour: 50% forgotten
- After 1 day: 70% forgotten
- After 1 week: 90% forgotten
- After 1 month: Nearly everything forgotten
Spaced repetition fights the forgetting curve by scheduling reviews right before you would forget. Each review strengthens the memory and extends the time until the next review is needed.
How It Works in Practice
Here's a simplified example:
- Day 1: Learn a new concept → review it
- Day 2: Review again (1-day interval)
- Day 4: Review again (2-day interval)
- Day 8: Review again (4-day interval)
- Day 16: Review again (8-day interval)
- Day 32: Review again (16-day interval)
Each time you successfully recall the information, the interval doubles. If you forget, the interval resets to a shorter period.
The Research Behind It
Spaced repetition isn't a study hack — it's one of the most well-researched techniques in cognitive science:
- Cepeda et al. (2006): Spacing study sessions improves retention by 10–30% compared to massed practice
- Karpicke & Roediger (2008): Repeated retrieval produces more learning than repeated studying
- Dunlosky et al. (2013): Rated spaced practice as one of the two most effective study techniques (alongside practice testing)
Spaced Repetition Tools
Anki (Manual Cards, Powerful Algorithm)
Anki is the gold standard for SRS power users:
- Free and open-source
- Highly customizable algorithm
- Massive community deck library
- Downside: Ugly interface, steep learning curve, manual card creation
Butterfast (AI Cards, Modern Interface)
Butterfast combines AI-generated flashcards with built-in spaced repetition:
- Upload a PDF, YouTube video, or audio → get flashcards automatically
- Built-in SRS scheduling (no setup required)
- Gamification (XP, levels, streaks) to maintain consistency
- Downside: Less algorithm customization than Anki
How to Start Using Spaced Repetition
Step 1: Choose Your Tool
If you want maximum control: Anki
If you want AI-generated cards with a modern UI: Butterfast
Step 2: Create or Generate Cards
With Butterfast:
- Upload your study material (PDF, YouTube, audio, text)
- Select "Flashcards" as output
- AI generates cards automatically with spaced repetition scheduling
Step 3: Review Daily
The key to spaced repetition is consistency. Review your due cards every day — it takes 5–15 minutes.
Step 4: Trust the Process
Don't review cards that aren't due. The algorithm knows when you're about to forget — trust it.
Common Mistakes
1. Making Cards Too Complex
Each card should test one concept. If your card requires remembering 5 things, break it into 5 cards.
2. Skipping Days
Missing a day creates a backlog. Consistency beats intensity.
3. Re-Reading Instead of Recalling
Don't flip the card immediately. Spend 5–10 seconds trying to recall before checking.
4. Cramming Before Exams
Spaced repetition works best over weeks and months. Start early.
FAQ
How long does it take to see results?
Most students notice improved recall within 1–2 weeks of consistent daily reviews.
Can I use spaced repetition for any subject?
Yes — it works for any subject that requires memorization: languages, medicine, law, history, science, programming.
How many new cards per day?
Start with 10–20 new cards per day. Too many creates an overwhelming review backlog.
Is Butterfast's SRS as good as Anki's?
Anki's algorithm is more configurable. Butterfast's advantage is that cards are generated automatically and the interface is modern with gamification built in.
Start Remembering What You Study
Stop forgetting 90% of what you learn. Use spaced repetition to build lasting knowledge.