How far apart to space your study sessions, based on when the test is

The rule in one line: the further off the test, the longer the gap

The table above is the whole rule. Look up your test date, pick the gap next to it, and put review days on a calendar one gap apart.

There are two things the table does not show. First, the gap is a share of the wait, and that share shrinks as the test moves further away. Second, being a little off costs little. A review every week or two for a test in two months is in the right zone. A review every hour on the last night is not.

Where the numbers come from

Spacing means splitting study into sessions with gaps between them. Its opposite is cramming: the same hours in one block. It is one of the most tested ideas in learning research.

In 2006, Cepeda and colleagues pulled together 839 assessments of spaced study, from 317 experiments in 184 articles. All used verbal tasks, like word lists and word pairs. Only 12 of 271 direct comparisons found no benefit from spacing, or a negative one. The review also found that the best gap grew as the time until the test grew.

Two years later the same group ran a large study of more than 1,350 people. People learned a set of facts, then reviewed them after a gap of up to 3.5 months. They took a final test up to a year after the review. For any test date, a longer gap helped at first. Past the best point, results fell off slowly.

That study gives the first and third rows of the table. It did not report a test two or three months away. The book reads between the two results and suggests about 1 to 2 weeks. It says plainly that this is its own estimate, not a published number, and we repeat that here.

The authors drew a sharp conclusion from the pattern: "many educational practices are highly inefficient." Most of us learned to study the week before, in one long push. The data point the other way.

What to do in each review session

The gap tells you when to come back. It does not tell you what to do once you are there.

The answer from the book is to make every review a test. Close your notes and write what you can recall, or run your flashcards cold. Then check. Rereading after a gap can help a little, as Dunlosky noted in 2013. Testing yourself after a gap does more.

How many reviews is enough? Rawson and Dunlosky (2011) ran three experiments with 533 students learning concepts, tested one to four months later. Their advice: practice each idea until you recall it correctly 3 times. Then relearn it 3 more times, in widely spaced sessions.

A big flashcard deck makes this hard to track by hand. The book's Three-Box Card System does the math for you. Cards you get right move to a box you see less often. Cards you miss go back to the front. The idea goes back to a card box from 1972 credited to Sebastian Leitner. No controlled trial of the box itself turned up, so the book badges it PROMISING, not SOLID. Its parts are each well supported.

Setting up your own Spacing Calendar

The Spacing Calendar is a SOLID tool from Stop Rereading. It takes about ten minutes to plan.

1. Write your test date and today's date. Count the days between.
2. Pick your gap from the table.
3. For each topic, mark the day you first learn it. Then mark review days, one gap apart, up to the test.
4. Make every review a recall session. Do not reread.
5. If you miss a review, do it as soon as you can. Then pick the gap up again from that day.
6. In the last week, add one or two short reviews of everything, a day or two apart.

Spacing: Less Cramming, More Coming Back has the full calendar, the Three-Box Card System and a worked example of a family planning for a final nine weeks out.

The 30-Day Plan at the back lays out a month of learning in chunks. Each chunk is reviewed the next day, then about 3 days later, a week later and two weeks later. The book is clear that the rhythm is its own reading of the research, not a tested schedule.

If your test is only days away, our page on an exam in a week fits these gaps into seven days.