Spaced Repetition Interval Planner
How it works
Spaced repetition is the most evidence-backed technique in learning science for long-term memorisation. Rather than reviewing material at fixed intervals, spaced repetition schedules reviews at increasing intervals calibrated to when you're most likely to forget — just before forgetting happens. The Spaced Repetition Interval Planner generates a personalised review schedule based on the SM-2 algorithm used by Anki, the most popular flashcard application.
**The forgetting curve** Hermann Ebbinghaus (1885) showed that memory decays exponentially if not reviewed: within 24 hours, ~60% of newly learned material is forgotten; within a week, ~75%. Each successful review resets and extends the retention period. A well-spaced review schedule produces the same long-term retention as massed practice with 8–10× fewer total review minutes.
**The SM-2 algorithm (basis of Anki)** After each review, rate your recall: 0 (complete blackout) to 5 (perfect). Interval calculation: - First review: 1 day - Second review: 6 days - Subsequent reviews: previous interval × ease factor (default 2.5, adjusts based on ratings) - If score < 3: reset to first review
**Optimal review timing** The goal is to review at approximately 80–90% retention probability — the "desirable difficulty" zone. Reviews too early waste time on well-remembered material; reviews too late rebuild a decayed memory (less efficient). The planner visualises your review workload over 30, 60, and 90-day horizons.
**What to memorise with spaced repetition** Medical school uses Anki for anatomy, pharmacology, and pathology. Language learners use it for vocabulary. Lawyers use it for case law. Developers use it for API signatures. The technique works best for discrete factual knowledge (vocabulary, dates, formulas, anatomy) rather than conceptual understanding (problem-solving, writing, analysis).
Privacy: all scheduling runs in the browser. No cards or data are transmitted.
Frequently Asked Questions
- Cramming (massed practice) concentrates all study in a short period before an exam. It works for short-term recall (the exam) but produces rapid forgetting — most crammed material is forgotten within days. Spaced repetition distributes practice over time with increasing intervals between reviews. The 'spacing effect' (first documented by Ebbinghaus, 1885) shows that spaced practice produces 2–3× better long-term retention per unit of study time. The cost is that spaced repetition requires planning ahead — it doesn't work well if you start 2 days before an exam.
- Anki (free, open source) is the gold standard: highly customisable, huge shared deck library, sync across devices, and based on the SM-2 algorithm. Used by medical students worldwide (Anki pre-built decks for Step 1 are common). Alternatives: Quizlet (simple, large community, paid tier for adaptive learning), Brainscape (confidence-based spaced repetition), Memrise (language learning with native speaker videos), RemNote (combines note-taking and spaced repetition). For language learning specifically: Duolingo uses a form of spaced repetition in its streak/review system.
- Daily maintenance reviews: 20–30 minutes per subject is typical for students with 200–500 mature cards in Anki. New cards per day: 10–20 new cards/day is sustainable for most subjects (learning 10 new items/day = 300/month). Avoid 'Anki bankruptcy' (falling 500+ cards behind) by keeping a consistent daily habit rather than large irregular sessions. In the early weeks, all cards are new and daily time can be higher (40–60 min); after 3–4 months, reviews stabilise at 15–25 min/day as cards reach longer intervals.
- Spaced repetition works best for factual knowledge requiring direct recall (vocabulary, anatomy, drug names, formulas, historical dates). For conceptual understanding (statistical reasoning, programming problem-solving, essay writing), spaced practice still helps — but the 'flashcard' format needs to change. Instead of fact cards, use problem cards: 'Describe the mechanism of action of beta-blockers' (not just 'what are beta-blockers?'). Working through practice problems at spaced intervals is effectively spaced repetition for procedural and conceptual knowledge. The principle transfers; the implementation differs.