We're the team behind Flips, a flashcard app that shows you a word right before you forget it. The engine at its core is spaced repetition. The name sounds technical, but the idea is simple. In this article we'll walk through what spaced repetition is, why it works, and exactly how to start using it yourself today.
Spaced repetition means widening the gaps between reviews
Spaced repetition is a method where you review something at gradually increasing intervals. Review once the next day, then a few days later, then a week, then a month — stretching the gap each time.
Compared to cramming everything at once (massed practice), the same number of reviews produces far more durable memory. This has been confirmed across many studies. The point isn't to do more — it's to do a little at the right moment. That's the essence of spaced repetition.
Why it works: turning the forgetting curve to your advantage
Human memory fades rapidly right after learning. That's Ebbinghaus's "forgetting curve." Spaced repetition makes this curve an ally rather than an enemy.
The key is recalling something just as it's starting to fade. Review at that precise moment — before it's gone, but late enough that it takes some effort — and the memory is strongly reinforced, flattening the curve. Each review extends how long until you'd next forget, so you can safely widen the gap. Repeat, and you reach long-term retention with the fewest reviews. By contrast, reviewing right after learning is low-effort and inefficient, and reviewing after total forgetting is close to relearning. Aiming for "just about to forget" is the best return on your time.
A starting guide: 1, 3, 7, 14, 30 days
So how many days between reviews, concretely? The exact answer varies by person and material, but a widely used starting guide looks like this.
| Review | When | Purpose |
|---|---|---|
| 1st | The next day | Stop the steep early drop |
| 2nd | ~3 days later | Firm up short-term memory |
| 3rd | ~1 week later | Move to mid-term memory |
| 4th | ~2 weeks later | Confirm retention |
| 5th | ~1 month later | Send to long-term memory |
What matters isn't following the numbers exactly, but the direction: short gaps right after learning, longer gaps as it sticks. Items you recall easily get pushed to a longer interval; items you miss get pulled back to a shorter one. That adjustment is where spaced repetition earns its keep.
Doing it yourself: paper cards and a calendar
You can start spaced repetition with no special tools. The minimum is a set of cards (question on front, answer on back) and a calendar. The steps: turn what you want to learn into cards → the next day, hide the answer and try to recall it → if you got it, write "next: 3 days" on the calendar; if not, write "again tomorrow" → when that day comes, recall again. Repeat per card.
The principle is simple, but there's a big trap here. As the number of cards grows, scheduling falls apart. With 50 or 100 cards, just sorting out "which cards are due today" becomes a daily chore. The reason most people abandon spaced repetition isn't that the method is hard — it's that the bookkeeping doesn't last.
Let an app handle it, and review becomes "just answer"
The practical move is to hand the interval math and sorting to an app. That's exactly why we built Flips — to make this management overhead disappear.
Flips uses the forgetting curve to calculate the "next review date" for every single word. All you do is answer the words that come up. Cards you get right move to a longer interval; cards you miss return sooner. You never have to figure out "what should I review today." It sends a push notification at the optimal time, so there's no staring at a calendar either. Both Card Mode and Quiz Mode are recall-based, so spaced repetition and active recall run together.
Spaced repetition is the single most effective way to make memorization efficient. Understand the principle, then offload only the tedious management to a tool — that, we believe, is the smartest way to use it today. Try Flips for spaced repetition that just keeps going, without the thinking.
Flips
The flashcard app that shows you words right before you forget them. Spaced-repetition timing calculated for you. Free to start.
Learn more about FlipsFrequently Asked Questions
What's the difference between spaced repetition and cramming?
Cramming (massed practice) packs everything into a short window, so you remember right after the test but forget quickly. Spaced repetition spreads reviews over time, so the same number of reviews lasts far longer. For anything you want to keep, spaced repetition wins.
Do I have to follow the intervals exactly?
No. The 1/3/7/14/30-day schedule is just a guide. What matters is the direction — short right after learning, longer as it sticks. Push easy items to longer gaps and pull missed items back to shorter ones.
Can I do spaced repetition with paper cards?
Yes — cards and a calendar are enough to start. But as the count grows, sorting out what's due today gets overwhelming and easy to quit. Beyond a few dozen cards, letting an app manage it is the better choice.
Does it work for things other than languages?
Yes. Spaced repetition works for memorization in general — exam terminology, historical dates, medical and legal vocabulary, and more. With Flips you can build your own decks for any subject.