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The number of days is the more interesting half of this page. A meta-analysis of 839 assessments of distributed practice found that the best gap between learning something and reviewing it grows with how long you need to hold on to it, and the largest experiment on the question put the optimum at about 20% of the delay from review to test. That is a figure you can actually schedule against. The hours box is the half the research has less to say about.
Last updated 1 October 2026
A date subtraction and a division, plus what the research says about the gap. This page counts whole calendar days to your exam and divides your planned hours by them. It does not know the format of the exam, what is on it, how much you already know, or whether those hours will be one block or fourteen, which is the thing that matters most. Nothing below is medical or psychological advice; it is what the published work on distributed practice reports, quoted, with the limits of each claim stated.
A countdown looks like a motivational widget. It happens to display the one variable that the best-evidenced finding in the study-skills literature is actually about.
That finding is distributed practice, or the spacing effect: material studied on separate occasions is remembered better than the same material studied for the same total time in one block. The reference work is Cepeda, Pashler, Vul, Wixted and Rohrer’s meta-analysis in Psychological Bulletin in 2006, and its scope is the reason it carries weight: “This review found 839 assessments of distributed practice in 317 experiments located in 184 articles.”
Its central result is not “spread your work out”, which everyone already says. It is that the right amount of spreading depends on how long you need to remember the material: “Analyses suggest that inter-study interval (ISI) and retention interval operate jointly to affect final test retention; specifically, the ISI producing maximal retention increased as retention interval increased.”
In plainer terms: the gap between studying something and coming back to it should be longer when the test is further away. There is no single correct study gap, and anything that tells you to review every three days regardless is leaving out the variable the research says the answer depends on. The exam date in the box above is that variable.
The 2006 meta-analysis established the shape of the relationship. The quantity came from a single very large experiment by the same group, Cepeda, Vul, Rohrer, Wixted and Pashler in Psychological Science in 2008. Its abstract is worth quoting at length, because the design matters for what you can take from it:
“To characterize spacing effects over significant durations, over 1350 individuals were taught a set of facts and – after a gap of up to 3.5 months – given a review on the same facts. A final test was administered at a further delay of up to 1 year. At any given retention interval, an increase in the inter-study gap at first increased, and then gradually reduced, test performance. The optimum gap value was about 20% of the test delay for delays of a few weeks, falling to about 5% when delay was one year. The interaction of gap and test delay implies that many educational practices are likely to be highly inefficient.”
Two definitions decide how to read that. The gap is the interval between first learning the material and reviewing it. The test delay is the interval between that review and the final test. The optimum is a ratio between them, and it is not a fixed number of days.
For a student, the exam is the final test, so the two intervals have to add up to the time you have. If you have D days and plan one review, then gap plus test delay equals D, and setting the gap at 20% of the test delay gives a gap of D divided by six.
The 20% ratio, worked out for one review before an exam
| Days until the exam | Review on about day | Exam then falls this long after the review |
|---|---|---|
| 14 days | 2 | 12 days |
| 21 days | 4 | 17 days |
| 35 days | 6 | 29 days |
| 70 days | 12 | 58 days |
| 365 days, at the 5% ratio | 17 | 348 days |
This table is arithmetic from the ratio the study reports. It is not a schedule the study tested, and the rows are rounded to whole days.
Now the caveats, which are the reason this page gives you one table rather than a planner.
That design used two study sessions. Learn, review once, test. A term of coursework involves lectures, reading, problem sets and several revision passes, and the paper does not say how to distribute n sessions. Extending a two-session optimum to a semester is an extrapolation, and it is mine rather than theirs.
The 20% figure is given “for delays of a few weeks”. The 12-day test delay in the first row of that table sits at or below the short end of what the experiment characterises well, so read the top rows as a direction rather than a prescription. The 5% figure is for a one-year delay, which is the regime a cumulative final or a professional exam might sit in.
It taught facts and tested recall of facts. Both Cepeda papers work with verbal material and recall. An exam that asks you to apply a method to a problem you have not seen is a different task, and these studies did not test it.
The authors’ own conclusion is a warning, not a recipe. “The interaction of gap and test delay implies that many educational practices are likely to be highly inefficient.” The claim is that timing has a large effect and is usually chosen badly. It is not that a particular calendar is correct for you.
A countdown tells you how many sessions you can fit. It says nothing about what should happen in one, and that turns out to be where most of the available gain sits.
John Dunlosky and colleagues reviewed ten study techniques for Psychological Science in the Public Interest in 2013 and rated each one by how well the evidence supported it. Writing about that review in American Educator the same year, Dunlosky gives the two definitions that matter here:
Those two were the winners, in his words: “We rated two strategies—practice testing and distributed practice—as the most effective of those we reviewed because they can help students regardless of age, they can enhance learning and comprehension of a large range of materials, and, most important, they can boost student achievement.”
Set against that are the methods most revision in the last week actually consists of. Dunlosky opens with highlighting, rereading and cramming the night before, and reports: “Quite often, students believe these relatively ineffective strategies are actually the most effective ... Unfortunately, in a recent review of the research, my colleagues and I found that these strategies are not that effective, especially if students want to retain their learning and understanding of content well after the exam is over.” On rereading specifically: “Despite its popularity, rereading has inconsistent effects on student learning”, and on how common it is, “A survey conducted at an elite university revealed that 84 percent of the students studied by rereading their notes or textbooks.”
He also explains why the better method loses: “In both cases, learning itself feels tougher when it is distributed instead of massed, but the competency and learning that students may feel (and teachers may see) during massed practice is often ephemeral.” Cramming works, in the sense that it produces a feeling of fluency on the night. The feeling is the problem, because it is evidence about the next hour rather than about Thursday.
And one concrete schedule, from the same article: “For any given class, two short study blocks per week may be enough to begin studying new material and to restudy previously covered material.” Two blocks a week per course, each one covering something new and something old, is a cheaper thing to set up than any plan the box above could generate, and it is what the person who ranked the methods recommends.
Total hours divided by days remaining. That is the whole calculation, and it is worth seeing it run so you know what you are looking at.
12 planned hours, at four different distances from the exam
The denominator is the number of days until the exam, which counts today and every day up to but not including exam day. So the row answers the question “if I do the same amount every available day, how much is that”, and it answers it correctly.
What it gets right is the direction. Dividing a total across the days you have, rather than leaving it in one block, is distributed practice in the sense Dunlosky defines it, and the research above says that is the side to err on.
What it cannot see is everything about the arrangement. Twelve hours as one Sunday and twelve hours as fourteen daily sessions produce the same 0.9 h/day row and are not the same preparation, because the gaps are the mechanism rather than a side effect of the total. The row also has no view on what happens in those hours, and the gap between testing yourself and rereading is wider than any pacing difference it can show you. Treat it as a sanity check on whether your plan fits in the time, not as the plan.
Worth stating exactly, because “days” is ambiguous and tools disagree about it. This page takes midnight today in your browser’s own timezone, takes midnight on the date you picked, subtracts, and rounds to the nearest whole day. So a day here is a calendar day, not a 24-hour period, and an exam at 9am and an exam at 5pm on the same date both read as the same number of days away.
Rounding is what makes that survive a clock change. From 1 October 2026 to 1 April 2027 the count comes out at 182 days, which is correct, even though in a timezone that moves its clocks forward in spring one of those days is only 23 hours long and the raw subtraction lands just short of 182. Spans that cross two changes cancel out.
Past dates are handled rather than refused: the headline switches from days until to days since, and the pace figure drops out, since there is nothing left to pace.
Whether your hours figure is right. You typed it. Nothing checks it against the size of the syllabus, and almost everyone underestimates. The reading page estimator at least puts a sourced rate behind the reading part of it.
How to arrange the sessions. It shows a flat daily figure. The research is about gaps, and a flat figure is only one of many arrangements that produce it.
What is on the exam. No syllabus, no topic list, no weighting, no past papers. A countdown that treats every exam as one undifferentiated block of hours is, by construction, not a revision plan.
What you already know. Twelve hours is a lot for a topic you half know and nothing at all for one you have not started, and the pace row is identical in both cases.
Whether hours are even the unit. The literature above counts sessions and the intervals between them. It does not report findings in hours of study, and this page has no field for a session or a gap.
Anything about you. This is a date subtraction. It is not advice about stress, sleep or concentration, it does not diagnose anything, and if the countdown is making things worse rather than better, the people to talk to are at your institution’s student services.
Every quotation and figure on this page was read against the sources above on 1 October 2026. Nothing you type leaves your browser. To map a whole term rather than one date, the semester date planner covers that end. More: the rest of the MyCampusKit tools.
The one quantified answer in the literature comes from Cepeda and colleagues (Psychological Science, 2008), who taught over 1,350 people a set of facts, reviewed those facts after a gap of up to 3.5 months, and tested at a further delay of up to a year: "The optimum gap value was about 20% of the test delay for delays of a few weeks, falling to about 5% when delay was one year." Applied to a single review before an exam, a 20% ratio works out as a gap of about one sixth of the time you have, so roughly day 6 of a 35-day run. That last step is arithmetic from their ratio, not a schedule they tested, and their design used exactly two study sessions rather than a term's worth.
For remembering it later, the evidence is strong and old. Cepeda and colleagues' 2006 meta-analysis in Psychological Bulletin "found 839 assessments of distributed practice in 317 experiments located in 184 articles", and concluded that the inter-study interval and the retention interval "operate jointly to affect final test retention; specifically, the ISI producing maximal retention increased as retention interval increased". Dunlosky adds the reason cramming survives anyway: "learning itself feels tougher when it is distributed instead of massed, but the competency and learning that students may feel (and teachers may see) during massed practice is often ephemeral".
Total study hours planned divided by the number of days until the exam, and nothing else. Twelve hours with the exam 14 days away gives 0.9 h/day. It counts today and every day up to but not including exam day, so with the exam tomorrow the same 12 hours become 12.0 h/day. If the exam is today or in the past there is no pace to show and the row reads as a dash.
No, and hours are the wrong unit for one. What the research counts is sessions and the gaps between them: the same twelve hours in one block and in twelve separate hours are not the same thing on a test two weeks later, and the gap is the entire mechanism. This page knows your total and your deadline and nothing about how the hours are arranged.
As whole calendar days in your browser's own timezone, from midnight today to midnight on the exam date, with the result rounded. Rounding is what makes it survive a clock change: from 1 October 2026 to 1 April 2027 it returns 182 days, which is right, even though in a timezone that puts its clocks forward one of those days is only 23 hours long. A day here is a calendar day, not a 24-hour period.
Dunlosky's review of ten study techniques rates two as the most effective: distributed practice, "implementing a schedule of practice that spreads out study activities over time", and practice testing, "self-testing or taking practice tests on to-be-learned material". Of highlighting, rereading and cramming he writes that "my colleagues and I found that these strategies are not that effective, especially if students want to retain their learning and understanding of content well after the exam is over". A countdown is a prompt to open a session; it has no opinion on what you do in it, and the difference between testing yourself and rereading is larger than anything on this page.
Yes, and the headline switches to counting days since instead of days until. That is deliberate rather than an error state, so an old date left in the box will still read sensibly. There is no pace figure for a date that has gone.