Spaced Repetition Calculator
Enter what you learned and when. This tool calculates when to review each item at expanding intervals, merges everything into one chronological review calendar, and exports it as an .ics file for your calendar app.
What did you learn?
Review dates per item
Combined review calendar
Why these intervals? Hermann Ebbinghaus showed in the 1880s that memory decays along a "forgetting curve": without review, most new material fades within days. Each well-timed review interrupts the decay and flattens the curve, so the next review can wait longer. That is why spaced repetition uses expanding gaps (1, 3, 7, 14, 30, 90 days) instead of cramming: a few minutes of review at the right moments beats hours of re-reading. Pair this schedule with active recall - test yourself instead of re-reading - for the strongest effect.