Spaced repetition: spaced reviews explained simply

The forgetting curve

As early as 1885, Hermann Ebbinghaus described how quickly we forget what we’ve learned without review – most of all shortly after learning it. Every successful review makes the memory more stable, so the next interval can be longer. Spaced repetition uses exactly this effect.

How the intervals are calculated

Many flashcard apps use variants of the SM-2 algorithm, developed in the late 1980s for the SuperMemo software. After each answer you rate how well you knew the card. From that, the algorithm calculates when the card comes back: later after a good answer, soon after a mistake.

Aynora uses a simplified SM-2 variant with four ratings: again, hard, good and easy. You rate with a button, the keys 1–4 or by swiping.

Using spaced repetition every day

• Study a little every day rather than for hours once a week – the due cards set the workload.
• Rate honestly: if you press “easy” too often, you’ll see hard cards too rarely.
• Start early: spaced reviews need days to weeks of lead time before an exam.
• Keep cards small: one fact per card is easy to rate clearly.
• Answer first, then flip: active recall is where the learning happens.

Spaced repetition with Aynora

Aynora creates the cards from your PDFs with AI and schedules the reviews automatically. A daily goal, a streak and optional push reminders help you stick with it. Free costs nothing and needs no credit card.