When a card comes back, and what your rating decides

A card does not come back on a timer: its next date is recalculated after every answer you give. You will need a deck you have already run through at least one session, or there is nothing to look at.

The first minutes: the card is still being learned

A new card starts in learning, and there the schedule is counted in minutes rather than days. Answer correctly and it returns in about ten minutes. Get it wrong and it returns after two other cards, and keeps coming back that way until you answer it correctly, with an easier question each time.

In a small deck you see this immediately: the same few cards come round every few shows. That is the intent. Until the knowledge comes back reliably, there is nothing worth postponing for days.

A card moves onto the calendar when two conditions hold together: two correct answers in a row, and a Correct rating in two different hard modes. Hard modes are the ones where you have to produce the answer yourself: typing it and filling a gap in a sentence, in either direction. Flip, multiple choice and matching pairs are not hard modes. A Hard rating keeps the streak going but does not close a hard mode: the card comes round again to give you a clean shot at it.

If the card carries only one hard mode, that one is enough. If it has none at all (say only flip and multiple choice are switched on), it moves on once every one of its modes has been rated Correct. The first calendar interval is always one day.

Days and weeks: how the interval grows

The second interval is about six days, and each one after that is the current interval multiplied by the card's "ease". Ease starts at 2.5 and moves with your ratings: Correct lifts it by about 0.1, Hard drops it by 0.14. It never leaves the range 1.3 to 3.0.

That is where the spread inside one deck comes from. A card you consistently rate Correct is months out after a few reviews. One that is a struggle every time gains days far more slowly and keeps coming back every week or two for a long time, which is not a fault but exactly what you want the schedule to do.

The mode you answered in also counts. Only the hardest mode available on that card extends the date in full; an easy one (multiple choice, matching pairs) gives less, so a lucky guess does not carry a card as far as an answer produced from memory. The comparison is made inside the card: if typing and gaps are switched off on it, whatever mode is left becomes its hardest.

What you choose with the rating button

① Wrong · ② Hard · ③ Correct — the three prices of one review.

In flip modes you set the rating yourself: Wrong, Hard or Correct. In graded modes the check sets it for you: an exact answer counts as Correct, an answer that is one or two characters off counts as Hard, anything else counts as Wrong.

"Full growth" in the right-hand column is a ceiling rather than a promise: it goes to an answer given in the card's hardest mode, and no earlier than the due date. The two dampers are below.

The rating answers one question: did you recall it, or did you peek? A Hard on a card you dragged out of memory after a pause serves you better than a Correct given out of politeness to yourself.

A mistake does not reset the card

A wrong answer on a card that already lived on the calendar does not send it back to the start. The card goes to relearning and returns after two other cards until you answer it correctly. To get back onto the calendar it needs two correct answers in a row, the second one no sooner than about ten minutes later. The correct answer right after the mistake counts as the first of the two: it comes from fresh memory and says nothing on its own about whether you will recall the card in a few days.

The interval the card returns to is shorter than the one you forgot it at: about a third of it, but never less than a day. Forget a card after twelve days, and twelve days is too long for it for now, so after relearning it comes back in three or four. Forget it there too, and the interval shrinks again until it lands on one you can hold. Ease drops by 0.2 along the way, so the interval grows more slowly from there. How often this has happened is the Lapses figure on the Statistics page.

Why an early review barely moves the date

When the cards due today run out, the session counter changes to "All required done · Early review" and you can keep going. But the growth of the interval is measured against how much of the planned wait you sat out. Answer a card on the same day you last saw it and the date barely shifts.

The same multiplier damps the gain in ease, so an evening of cramming cannot accelerate future dates by the back door: twenty correct answers in a row will not send a card half a year out. For the same reason Drill card (the mode that narrows the session to a single card) credits exactly one answer: the repetitions after it change neither the schedule nor today's progress.

Where to see what is happening to your memory

The Memory section on the Statistics page sorts your cards into four states:

• New. You have not started them;
• Learning. Being learned or relearned, scheduled in minutes;
• Consolidating. On the calendar, but still on a short interval;
• Long-term. The interval has reached three weeks or more.

All four cards of this deck are still Learning: their schedule is counted in minutes.

The share of that last state is also shown on the page as its own figure, Long-term. It moves slowly, and that is the point: it measures memory rather than how much you did today.