Spaced Repetition Schedules Explained: Find Your Perfect Interval

What Is a Spaced Repetition Schedule?

A spaced repetition schedule is a sequence of increasing time intervals between reviews of the same material. The goal is to test your memory right before you are about to forget it (usually when you have a ~90% chance of recall).

If you review too soon, you waste time. If you review too late, you forget and have to re-learn, which takes more effort.

The SM-2 Algorithm Explained

Created by Piotr Woźniak in the late 80s for SuperMemo, SM-2 is the industry standard (used by Anki and SpaceRep). It works by assigning an "Ease Factor" (EF) to every card.

FSRS vs SM-2: Which Is Better?

FSRS (Free Spaced Repetition Scheduler) is a newer algorithm based on machine learning. It claims to result in 20-30% fewer reviews for the same retention rate compared to SM-2.

However, FSRS requires a lot of review history to "train" itself on your brain. For most beginners, SM-2 is robust, proven, and requires zero configuration.

Standard Spaced Repetition Intervals

If you were doing this manually (without an algorithm), a common schedule looks like this:

Sample Schedules for Different Goals

1. The "Exam in 2 Weeks" Schedule (Aggressive)

You can't do true spaced repetition in 2 weeks, but you can do a compressed version.

• Day 0: Learn
• Day 1: Review
• Day 3: Review
• Day 6: Review
• Day 10: Review

2. The "Language Fluency" Schedule (Conservative)

For vocabulary, you want to be very sure before moving on.

• Day 0: Learn
• Day 1: Review
• Day 2: Review (Extra check)
• Day 4: Review
• Day 8: Review