Spaced repetition schedule calculator

The forgetting curve in numbers

Hermann Ebbinghaus measured how much of a list of nonsense syllables he still remembered after different delays. The figures below are the savings percentages usually quoted from his 1885 experiment: memory drops fast at first and then levels off, which is why early reviews are close together.

These come from a single experiment on one person using meaningless syllables. Real material, sleep, interest and how well you learned it change the curve, so use them as a rough guide, not a prediction.

Common interval patterns

Each number is the day of a review counted from the first study day. Start with the standard pattern and move to a gentler or longer one if you keep forgetting or need the cards for months.

How many days to introduce every card

Days needed to introduce all the cards at a fixed number of new cards per day. The last review of the final card comes later, after the longest interval.

FAQ

What is a good spaced repetition schedule?

A common starting point is to review on day 1, 3, 7, 14 and 30 after you first learn something. The gaps grow because each successful recall makes the memory last longer. If you keep forgetting cards, add an extra early review (1-2-4-7-14-30); if you need the material for months, extend the pattern to 60 and 90 days.

How does the forgetting curve relate to review intervals?

Without review, memory falls steeply in the first day and more slowly afterwards. Reviewing just before you would forget resets the curve and makes the next drop slower, so each interval can be longer than the last. That is why schedules double or nearly double the gap after every review.

How many new cards should I add per day?

It depends on how much time you have for reviews, because every new card comes back several times. With a 5-review pattern, adding 20 new cards a day means about 100 reviews a day once the schedule is in full swing. The table above shows how many days it takes to introduce a deck at 10, 20, 30 or 50 cards a day.

What if I miss a day or fall behind?

Do the overdue cards first, then continue; it is better to review late than to skip a review. If many cards are overdue, pause new cards for a few days until the backlog is cleared. The calculator assumes you keep up, so treat its dates as a plan, not a deadline.