About the Spaced Repetition Scheduler
This spaced repetition scheduler turns the day you first learned something into a list of review dates. Each review is spaced further apart than the last, because memory research consistently shows that reviewing just as you are about to forget strengthens recall far more than cramming the same number of sessions into one evening.
Choose a schedule: the popular expanding 1-3-7-14-30 day pattern, Leitner-box doubling (1, 2, 4, 8 days apart…), the SuperMemo SM-2 algorithm used by flashcard apps such as Anki, or your own custom list of days. The table lists every review with its weekday, the gap since the previous review and the days since you first studied, ready to copy into a calendar or planner.
It is useful for students preparing for exams, language learners, medical and law students working through large decks, and anyone who wants a simple paper or calendar system instead of an app. The SM-2 option assumes you recall the material every time with the same quality grade; a real app would restart the sequence after a failed review.
How to use the spaced repetition scheduler
- 1Enter the date you first studied the material.
- 2Pick a schedule — expanding days, Leitner doubling, SM-2 or your own list.
- 3Choose how many reviews you want to plan.
- 4For SM-2, choose how well you expect to recall the material each time.
- 5Copy the review dates from the table into your calendar or planner.
Formula and method
Every schedule is converted to "days after the study day" and added to your start date. The expanding schedule uses the widely taught 1, 3, 7, 14, 30, 60, 120… day checkpoints. The Leitner option doubles the gap after each successful review, which is what happens when a card moves up one box in a Leitner box system.
The SM-2 option follows Piotr Woźniak’s published SuperMemo-2 algorithm: the first interval is 1 day, the second 6 days, and every later interval is the previous one multiplied by the item’s ease factor (EF) and rounded up. EF starts at 2.5, is adjusted after each response of quality q (0–5) and never drops below 1.3. A grade of 4 leaves EF unchanged, 5 raises it by 0.1 and 3 lowers it by 0.14 per review. Woźniak defines I(n) as the interval after the n-th repetition, so your first study session counts as repetition 1 and its grade already updates EF before the third interval is calculated. Reviews that would fall more than 50 years out are left off.
- I(n)
- Gap in days before review n
- EF
- Ease factor (starts at 2.5, minimum 1.3)
- q
- Recall quality grade from 0 (blackout) to 5 (perfect)
- k
- Review number in the Leitner sequence
Worked examples
Expanding schedule from 5 January 2026
Reviews fall 1, 3, 7, 14, 30 and 60 days after 5 January: 6 Jan, 8 Jan, 12 Jan, 19 Jan, 4 Feb and 6 Mar. The longest gap is the 30 days between 4 February and 6 March, and six 15-minute reviews take 90 minutes (5,400 seconds).
Leitner doubling for an exam
Gaps of 1, 2, 4, 8 and 16 days put the reviews on days 1, 3, 7, 15 and 31 after 2 March, so the last review is on 2 April. Five 20-minute sessions add up to 100 minutes.
SM-2 with perfect recall
With grade 5 the ease factor rises by 0.1 after every response: 2.6, 2.7, 2.8, 2.9, 3.0. The gaps are 1 and 6 days, then ⌈6 × 2.8⌉ = 17, ⌈17 × 2.9⌉ = 50 and 50 × 3.0 = 150 days, so reviews land 1, 7, 24, 74 and 224 days after 1 September — the last on 13 April 2027.
Frequently asked questions
What is the best spaced repetition schedule?+
There is no single best schedule, but expanding gaps that roughly double or triple each time work well for most learners. Adaptive algorithms such as SM-2 adjust the gap to how easily you remember each item, which is why flashcard apps use them.
What are the 1-3-7 or 1-3-7-14-30 review rules?+
They are simple expanding schedules: review one day after learning, then three days, seven days, two weeks and a month after the original session. They are easy to follow on paper and approximate what adaptive algorithms produce for well-known material.
How does the SM-2 algorithm calculate intervals?+
SM-2 sets the first interval to 1 day and the second to 6 days. Each later interval is the previous interval multiplied by the ease factor, rounded up. The ease factor starts at 2.5 and changes after every review depending on how well you recalled the answer.
What happens if I miss a scheduled review?+
Review as soon as you can and continue from there; a late review is still far better than skipping it. If you have forgotten the material, treat it as newly learned and restart the sequence from the first short gap.
How many reviews do I need to remember something long term?+
For exam material, five or six well-spaced reviews over two to three months usually keep recall high. For lifelong retention, intervals keep growing to many months, so each item needs only occasional reviews once it is well learned.
What is the Leitner system?+
The Leitner system stores flashcards in numbered boxes. A correctly answered card moves to the next box, which is reviewed less often; a missed card goes back to box one. Doubling the gap for each box gives the 1, 2, 4, 8, 16 day pattern used here.