What is the 2-3-5-7 spaced repetition method?

What is the 2-3-5-7 spaced repetition method? It is a fixed revision schedule: after you first learn something, you review it on day 2, then day 3, day 5, and day 7. The idea is to catch each item just as it starts to fade, which is the real spacing effect at work. But the specific numbers are a study-blog rule of thumb, not a result from any paper. They spread on exam-prep and GCSE revision sites (you will also see it written "2/3,5/7"), and they treat every fact the same way, whichever ones you find easy or hard. That is the difference from an algorithm like FSRS, which times each card to your own recall instead of a one-size timetable.

For a handful of exam facts, a fixed 2-3-5-7 timetable is fine, and better than cramming. For hundreds of words across months, a schedule that adapts to how well you actually remember each one saves a lot of pointless reviews. Here is how an adaptive schedule decides each interval.