Spaced Repetition Review Schedule Calculator

Spaced Repetition Schedule (SRS)

Spaced repetition exploits the forgetting curve: memory retention drops fast at first, then slowly. By reviewing at expanding intervals, you reinforce memory just before it would have been lost, which minimises total review time while keeping retention high.

Interval versus due date, which are not the same number

An SRS interval is the gap since the last review, not the days since you first learned the card. With the default 2.5 ease the gaps run 1, 3, 6, 16, 39, 98 days, so the sixth review falls on day 163, not day 98. The table this calculator prints gives both columns, because mixing them up is the single easiest way to plan a review calendar that is weeks out of step with reality.

The standard formula: Next interval = Last interval × Ease factor

Where the ease factor varies by recall confidence:

Where the daily review number comes from

In a steady state you add the same number of cards every day, so on any given day the cards coming due are one cohort per due date that fits inside the deck’s age. That makes the load

Daily reviews = New cards per day × (number of due dates within the deck's age)

With default ease, six due dates fall inside the first year (days 1, 4, 10, 26, 65 and 163), so 15 new cards a day settles near 90 reviews a day by the twelve-month mark. Push out to three years and two more due dates come inside the window, taking it to 120. The load climbs, but logarithmically, not in step with the deck.

A different number you will see quoted: for a mature deck of N cards that has stopped taking new material, average daily reviews land near N / 200, so a finished 10,000-card deck costs about 50 a day. That figure and the one above describe different situations, and the gap between them is the whole cost of still adding cards.

Interval caps. Anki’s default maximum interval is 36,500 days, which effectively means no cap, and the arithmetic here follows that. Most people set theirs to a year or two. A cap raises the long-horizon daily load, since a card capped at 365 days keeps coming back instead of drifting out to a decade.

Practical settings:

• Beginner: 5-10 new cards/day
• Intermediate: 10-20 new cards/day
• Advanced: 5-15 new cards/day (most time on review, not new)
• Cramming for an exam: 20-30 new/day with shorter intervals (lower ease)

Why this works: The 2.5× expansion was determined experimentally by Piotr Wozniak (SuperMemo, 1985) and validated by Anki users tracking millions of reviews. Cards reviewed at well-spaced intervals have ~90% recall vs. ~50% for cramming.

Common mistakes:

• Marking cards “Easy” too often → intervals expand too fast → forgetting
• Marking “Hard” too often → intervals barely grow → time waste
• Skipping days → backlog of due cards → demotivation cascade
• Ignoring “leeches” (repeatedly failed cards) → suspend or rewrite