What is spaced repetition? A beginner's guide

Updated March 2026 · 5 min read

Spaced repetition is a study technique where you review information at increasing intervals over time. Instead of cramming everything the night before an exam, you spread your reviews out — and the result is dramatically better long-term retention.

The forgetting curve

In 1885, psychologist Hermann Ebbinghaus discovered that we forget new information in a predictable pattern. Within 24 hours of learning something, you'll forget roughly 70% of it — unless you review it. Each time you review, the memory gets stronger and takes longer to fade.

Spaced repetition exploits this by timing your reviews right before you're about to forget. This is the most efficient way to move information from short-term to long-term memory.

How SRS algorithms work

A Spaced Repetition System (SRS) is software that automates this process. After you review a flashcard, you rate how well you remembered it:

• Again — you forgot. The card comes back in minutes.
• Hard — you struggled. The card comes back in a day or two.
• Good — you remembered. The card comes back in several days.
• Easy — instant recall. The card comes back in weeks or months.

The algorithm adjusts the interval for each card individually. Over time, well-known cards appear very rarely while difficult cards keep coming back until you've mastered them.

Who uses spaced repetition?

• Medical students — memorising thousands of terms, drug names, and anatomy
• Language learners — building vocabulary in a new language
• Law students — case law, statutes, and legal principles
• Programmers — API references, keyboard shortcuts, algorithms
• Anyone preparing for exams — GCSEs, A-levels, university finals, professional certifications

How to get started

1. Choose an SRS app. Popular options include Anki (desktop), AnkiMobile (iOS, $24.99), and sumi (iOS, free).
2. Create or import flashcards. Keep cards simple — one fact per card. Use cloze deletions for fill-in-the-blank style.
3. Review daily. Consistency matters more than volume. Even 10 minutes a day builds strong long-term memory.
4. Trust the algorithm. Don't skip cards or override the schedule. The system works best when you follow it.

Tips for effective flashcards

• Keep cards atomic — one concept per card
• Use your own words, not copy-pasted text
• Add context — "The capital of Japan is {{Tokyo}}" is better than "Tokyo = ?"
• Use images where they help (anatomy diagrams, maps, charts)
• Review in short, frequent sessions rather than long marathons

The research

Spaced repetition is one of the most well-studied learning techniques in cognitive science. A comprehensive review published in Psychological Science in the Public Interest found that distributed practice (spacing) was one of only two study techniques rated as having "high utility" — the other being practice testing, which is exactly what flashcards provide.

Try spaced repetition with sumi

Free flashcard app for iPhone with built-in SRS. Import your Anki decks or create your own.