Flashcard Progress Calculator

Flashcard progress is governed by two competing flows: new cards entering the deck and review cards falling due. Introducing cards at a constant rate makes the first flow linear, so remaining cards divided by new cards per day gives the days needed to see everything once. The review flow, by contrast, grows with the size of the learned pool, which is why daily study time rises for several weeks before it plateaus. This calculator estimates reviews per card as five divided by your retention rate, so a learner holding 85 percent retention needs about six successful passes per card, while 70 percent retention pushes that toward eight. The Leitner box display maps the learned portion of the deck onto the classic five-box interval ladder of 1, 3, 7, 14, and 30 days. Practitioner ranges are fairly stable. Between 10 and 30 new cards per day is sustainable for most learners; medical and law students push 40 to 60 during dedicated study blocks; and retention below 80 percent usually signals overloaded card design rather than a scheduling problem. Average handling time runs about 8 to 12 seconds for a mature review and 20 to 30 seconds for a first exposure. The model assumes uniform card difficulty and perfect daily attendance. Real decks contain a minority of leeches that absorb a disproportionate share of reviews, and skipped days compress future workload into a backlog.

The box method modelled here comes from Sebastian Leitner, a German science journalist, who described it in his 1972 book So lernt man lernen, published in English as How to Learn to Learn. Leitner proposed a physical card file divided into compartments: a card answered correctly moved one compartment back and was seen less often, while a card answered wrongly returned to the first compartment. The scheme gave ordinary learners a mechanical way to concentrate effort on weak items without keeping records. Five years earlier, Paul Pimsleur had published A Memory Schedule in the Modern Language Journal in 1967, setting out graduated interval recall for language learning with intervals expanding from seconds to years. Computers replaced the card box in the 1980s. Piotr Wozniak, then a student in Poznan, Poland, began recording his own recall data in 1985 and later released SuperMemo for DOS, publishing the SM-2 algorithm in 1987, which introduced the per-card ease factor. Damien Elmes released Anki in 2006 using a modified SM-2 scheduler, and shared decks made large-scale flashcard study routine in medical education. All of these systems descend from Hermann Ebbinghaus's 1885 self-experiments on memorising nonsense syllables, which first quantified how quickly unreinforced material is lost.