Spaced repetition is a study technique where you review material at increasing intervals — a day after you learn it, then a few days later, then a week, then a month. Each review comes just as the memory starts to fade, which is the most efficient moment to strengthen it. It's one of the most reliable findings in learning research, and it's the engine inside Koydo Flashcards.
The short version
•Review at growing gaps — roughly a day, a few days, a week, then weeks and months.
•A handful of well-spaced reviews outperforms many repetitions crammed together.
•The small effort of recalling a fading memory is what makes it durable.
•Software (or Koydo) handles the scheduling so you don't have to.
The idea in one sentence
Memory fades on a curve, and a well-timed review resets that curve higher than before — so the next review can wait even longer. Spacing your reviews out, rather than repeating something many times in one sitting, is what moves material into long-term memory.
Why spacing beats cramming
Cramming packs many repetitions into a short window. It feels productive because the material is easy to recall in the moment — but that fluency is temporary, and most of it is gone within days.
Spreading the same number of repetitions over days and weeks feels harder, because each time you return the memory has faded a little and you have to work to retrieve it. That effort is exactly what makes the memory durable. Researchers call this the spacing effect, and it has been confirmed across hundreds of studies (see our sources page).
How to actually do it
You can run spaced repetition by hand with paper cards and a box, scheduling each card forward as you get it right. But tracking dozens or hundreds of cards quickly becomes a chore — which is why most people use software that schedules every review automatically.
In Koydo, you never set intervals yourself: the app brings each card back at the right moment, so you just study what comes up each day. If you want to see the schedule a spaced system produces, try our free spaced repetition calculator.
Frequently asked
How is spaced repetition different from just reviewing?
Plain reviewing repeats material on no particular schedule, often all at once. Spaced repetition times each review to land just as the memory begins to fade, and stretches the gaps out as the memory strengthens — which is far more efficient.
What's a good spaced repetition schedule?
A common pattern is to review about a day after first studying, then around three days, a week, a couple of weeks, then a month or more. The exact gaps depend on how well you want to remember — our spaced repetition calculator shows the schedule for any target.
Does spaced repetition work for any subject?
It works best for facts, vocabulary, definitions, formulas, and other discrete pieces of knowledge — the kind of material flashcards are made for. For skills like problem-solving, pair it with practice and interleaving.
How many reviews until something is in long-term memory?
Often just four to five well-spaced, successful reviews are enough to hold a fact for a year or more. Each successful review buys you a longer gap before the next one.