Spaced Repetition Calculator

Enter your exam date and when you first studied each topic. The calculator spaces out your reviews, with gaps that grow as the material sticks, and gives you the dates as a calendar file.

How to Use the Spaced Repetition Calculator

1. Set your exam date, or tap one of the quick options.
2. Add what you're learning. One row per topic, chapter or lecture, with the day you first studied it. Topics you haven't started yet can have a date in the future.
3. Read your schedule. Each date lists the topics to review that day, and every topic gets a final review the day before the exam.
4. Add it to your calendar. The calendar file creates an all-day event for each review day from today on. You can also copy the plan as text or print it.

Your plan is saved in this browser, so you can come back and add topics as the course goes on.

How the Spaced Repetition Schedule Is Built

Spaced repetition means reviewing material at increasing intervals instead of all at once. The tricky part is choosing the intervals, and the right answer depends on how far away the test is.

The calculator follows a large online study by Nicholas Cepeda and colleagues (2008). They had people learn a set of facts, review them after gaps of up to about three months, and take a test up to a year later. The best gap between study sessions grew with the time until the test, but as a share of it, it shrank: roughly 20 to 40% of the time left for a test a week away, and roughly 5 to 10% for a test a year away.

Here's how the calculator uses that:

• The first review is the day after you study. Then each gap is double the last one.
• The gaps stop growing at a ceiling set by the research above. The further away your exam, the longer the ceiling, but the smaller it is as a share of the time you have.
• The last review is the day before the exam, so everything is fresh.

This is a rule of thumb based on research, not a personalized algorithm. Flashcard apps like Anki go further and adjust each card's next review based on whether you remembered it. The two work well together: use the calculator to decide when to sit down with a topic, and Anki for the individual facts inside it.

How to Make Each Review Count

A review only helps if you make your brain work for the answer. Rereading your notes feels productive but does little; a 2013 review by John Dunlosky and colleagues rated rereading low and practice testing high.

• Test yourself first. Close your notes and write down, or say out loud, everything you remember. Then check what you missed. That's active recall.
• Explain it simply. If you can't explain a topic to a twelve-year-old, the Feynman technique shows you where the gaps are.
• Use your notes' cue column. If you take Cornell notes, cover the right side and answer the questions on the left.
• Keep reviews short. A focused 20-minute round of self-testing is much easier to repeat on a dozen review days than an hour of rereading. A Pomodoro timer helps you stop on time.

Frequently Asked Questions

What is the best spaced repetition schedule?

The best schedule depends on how long you need to remember the material. Start with a review the day after you learn something, then let the gaps grow, with a longer limit the further away your test is. Following the research above, the calculator lets the gaps grow to about five days for an exam a month away, and to three or four weeks for one a year away.

What if I miss a review?

Do the review as soon as you can, then carry on with the next date as planned. One late review costs you much less than giving up on the schedule. If you fall far behind, change the "first studied" date to today, and the calculator will build a fresh schedule from there.

Should I use this calculator or Anki?

Use both if you can. The calculator plans when to review whole topics before a fixed exam date. Anki schedules individual flashcards based on how well you remember each one, which is better for vocabulary, formulas and other facts you need to know cold.

How do I add the schedule to Google Calendar?

Click Add to calendar to download the file. Then, on a computer, open Google Calendar, go to Settings, choose Import & export, select the file and click Import. On an iPhone or Mac, opening the file lets you add the events to Apple Calendar. Outlook can open or import the same file. If you change your plan later, delete the old review events before importing the new file, because not every calendar app replaces them.

Does spaced repetition work for every subject?

It works for most subjects where you need to remember what you learned. In the Dunlosky review mentioned above, distributed practice earned its high-utility rating partly because it had helped across a wide range of learners, materials and tests. It works best alongside self-testing, so turn each review into a quiz rather than a read-through. Our guide on how to study effectively covers the other techniques worth combining with it.