SM-2 Spaced Repetition Calculator
Compute the next review interval and updated ease factor for a flashcard using the SuperMemo SM-2 algorithm used by Anki and most spaced-repetition apps.
How to Use the SM-2 Spaced Repetition Calculator
- Enter the current interval in days and ease factor (new cards start at EF = 2.5).
- Pick the quality grade for the most recent answer.
- Click Calculate to see the new interval and ease factor.
Anwendungsfälle
- •Building custom flashcard apps.
- •Planning study schedules.
- •Teaching the psychology of memory.
Formel
EF_new = EF_old + (0.1 − (5 − q)(0.08 + (5 − q) · 0.02)), clamped at 1.3. Interval: q < 3 → 1 day, otherwise round(interval × EF_new).
Häufig gestellte Fragen
Why clamp EF at 1.3?
SM-2 floors the ease factor to avoid "leech" cards collapsing to a review-every-day state. Anki uses the same floor by default.
Is the first interval always 1?
In pure SM-2 a new card is reviewed again after 1 day, then 6 days, then interval × EF. Anki tweaks this slightly with initial steps.
How does q < 3 work?
Any grade below 3 resets the interval to 1 day but still updates the ease factor, so repeated failures gradually make the card easier (smaller intervals).