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 — minimizing total review time while maximizing retention.

The classic SuperMemo / Anki interval pattern:

• Day 0: Initial learn
• +1 day
• +3 days
• +7 days
• +14 days
• +30 days
• +90 days
• +180 days
• +365 days
• … continues with interval × ease factor (~2.5×)

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

Where the ease factor varies by recall confidence:

Average daily review load: For a steady-state deck of N cards, average daily reviews ≈ N / 200 at default ease. So a 10,000-card mature deck = ~50 reviews per day.

Adding new cards: Each new card creates 5-10 reviews in its first month, then 2-3 reviews per quarter. Adding 20 new cards a day balances out at ~50-80 reviews/day after 3-6 months.

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