Cramming works, for about a day. Spread the same hours across a couple of weeks and you remember more, for longer, with less total effort. The catch is knowing when to review each thing, which is where most people give up and go back to rereading everything the night before.
The forgetting curve#
After you learn something, your chance of recalling it drops: quickly at first, then more slowly. Each time you successfully review it, the curve flattens. The memory lasts longer before it fades, so the next review can wait longer.
That gives you the core rule of spaced repetition: review right before you’d forget. Too early and the review does little, because recall was easy. Too late and you’re relearning from scratch. Just before forgetting, the effortful recall is what makes the memory stick.
How big should the gaps be?#
It depends on how long you need to remember. A large study had people learn facts, review them after a gap, and take a test much later. The best gap grew with the time until the test, but more slowly: for a test a week away, reviewing after a day or two worked well; for a test months away, the best gap was weeks.1
Day 0
Learn it
Read, understand, and test yourself once before you stop.
Day 1
First review
Short and effortful. Most forgetting happens in the first day.
Day 3–4
Second review
If it came back easily, push the next one further out.
Day 8–10
Third review
Mix it in with other topics.
Week 3+
Long-term
Gaps keep growing as long as you keep getting it right.
These are rough numbers. In reality every card has its own curve: the definition you nailed on day one needs far less review than the formula you keep mixing up.
How Cramby schedules your cards#
Cramby schedules flashcards with FSRS (the Free Spaced Repetition Scheduler), a modern open-source algorithm. For every card it tracks two things:
- Stability: how many days the memory lasts before your recall drops to the target.
- Difficulty: how hard this particular card is for you, which controls how fast its stability grows.
Each grade you give updates both, and the next review is set for when your chance of recalling it falls to about 90%. You can see the result on the grade buttons: they show when the card will come back for each answer before you pick one.
Grading yourself honestly#
The schedule is only as good as your grades. A quick guide:
Grade this
- Again
- Hard
- Good
- Easy
When
- You couldn’t recall it, or got it wrong
- You got there, but it took real effort or you were unsure
- You recalled it with a normal amount of thought
- Instant and certain. Use sparingly
Pressing Good on a card you half-remembered feels kind, and costs you later: the card disappears for too long and comes back forgotten.
Making cards that work#
- One idea per card. “List the 6 causes of…” is six cards, or a quiz question, not a flashcard.
- Ask for production, not recognition. “What does the Calvin cycle produce?” beats “The Calvin cycle produces G3P: true or false?”
- Add the why. Cards with a short reason on the back are easier to rebuild when you half-forget.
- Turn mistakes into cards. Questions you miss in quizzes are the best cards you’ll ever make.
The short version
- Review right before you’d forget: that’s when recall builds the most memory.
- Gaps should grow, and the best gap depends on when you need to remember.
- Cramby uses FSRS to schedule each card on its own curve, aiming for 90% recall.
- Grade honestly. Again and Hard are what make the schedule fit you.
Sources
