How many hours to study for an exam (and how to work it out)

If you're looking up how many hours to study for an exam, the honest answer is that there's no single number that works for everyone, but there is a way to figure out yours in about ten minutes. It depends on how much material is covered, how much you understood in lecture, what kind of exam it is and what grade you're aiming for. What holds for almost everyone: a few hours spread over several days beat a lot of hours crammed into the night before, and an hour of practice is worth more than an hour of rereading.

The usual mistake isn't studying too little. It's not knowing how much you need until it's too late. You open the course folder on Thursday, find twelve lectures of thirty slides each, and the midterm is Monday. What follows is how to avoid that last-minute math: how to estimate the hours before you start, how many actually count in a day, and how to spread them out.

I'll use one concrete example throughout: a Principles of Economics midterm covering twelve lectures, each with a slide deck and a textbook chapter or two. The numbers are from that example and from how I plan my own studying; adjust them to your course.

Work out the hours from the material, not from panic

"How many hours?" is easier to answer backwards: first look at what you need to study, then put time on each piece. Do it before you start, with the syllabus and the files open:

1. List what's covered. Every lecture, every reading, every problem set. In the example: twelve slide decks, four chapters and one problem set.
2. Rate each topic. Green if you understood it in lecture, yellow if sort of, red if you missed it or it went over your head.
3. Give each color a time. A green topic needs review and practice; a red one needs to be learned from scratch. I budget two or three times as long for a red as for a green.
4. Add practice separately. Taking a full past exam under time, grading it and going back over what went wrong takes its own block of time.
5. Add a buffer. Something always takes longer than you thought.

The number you get is yours, not one from a Reddit thread. If it comes out to twenty hours and you have four days, you know it's five a day, or that something has to go. If it's forty and you have two days, better to find out now than on Sunday night.

You'll also hear the old rule of thumb of two to three hours of study outside class per credit hour each week. It's useful for planning a semester, but for a specific exam the count from your own material is much more accurate.

In the economics example, with five lectures in green, five in yellow, two in red and two past exams to practice with, the count comes to about eighteen hours. That isn't a universal figure: it's what that material takes for that student.

How many hours a day actually count

Even with a free day, you won't get ten good hours of studying out of it. You get far fewer hours with your brain switched on, and the rest is seat time: you're sitting in front of the material, but nothing's going in.

A few signs you've stopped studying:

• You read the same slide three times and can't say what it's about.
• You drift back to rereading and highlighting because practice feels too hard.
• You check your phone every few minutes without noticing.

That's why it helps to think in blocks instead of loose hours. A fifty-minute block with a short break, or the pomodoro technique if that suits you better, with a daily limit you can keep up for several days in a row. For a lot of people that looks more like three or four hours of real studying than eight. If you hit more on a good day, great; if it leaves you wiped out for the next one, it didn't pay off.

What matters isn't your record for one day, it's a pace that lasts until the exam. Five days of three solid hours almost always beat one twelve-hour marathon followed by four days of nothing.

Spread out beats crammed

This is one of the most solid findings in learning research: what you study across several separate sessions is remembered better than the same material studied in one go. It's called the spacing effect, and it's why the same number of hours gives different results depending on how you split them.

In practice that means two things:

• Start earlier, even with fewer hours. Eighteen hours over six days beat eighteen hours over two.
• Come back to every topic more than once. Day one you learn it, a couple of days later you review it by trying to recall it, and the day before you practice it.

I go deeper into this in spaced repetition. Every pass over a topic takes less time than the last, so your total time shrinks as you go, which is why the last few days feel lighter when you start early.

Where the hours actually go

Knowing how many hours you have is half of it. The other half is what you spend them on, because not every activity pays off the same.

Rereading and highlighting eats the most time and leaves the least behind. It feels like progress because everything looks familiar, but recognizing something isn't the same as being able to explain it on the exam.

Practicing by recalling gives you the most per hour: closing your notes and writing down what you know about a topic, working problems without looking at the solution, answering past exam questions. It's harder, and that's exactly why it works.

Figuring out what you didn't get is what eats time without you noticing. A slide with three words and a graph that got ten minutes of explanation in lecture can cost you half an hour of digging through the textbook. That's where Filmina, a web app that explains your lecture slides out loud, one at a time, pointing at the part it's talking about, can help, and you can ask Mina about your own material when something doesn't click. It needs an internet connection and the free plan has a monthly cap on minutes, so use it for your red and yellow topics, not for what you already know.

A rule that works for me: at least half your hours should be practice, not reading. If all you did today was read, the day counts for less than the hours you sat there.

When the hours don't add up

Sometimes the count comes out higher than the time you have. It happens, and it's not the end of the world. What doesn't work is skimming everything equally fast and learning nothing properly.

What does work:

1. Prioritize by what the exam weighs. Look at past exams and the syllabus: which topics always show up and which almost never do. The regulars go first.
2. Do yellows before reds. A topic you almost understand takes little time to finish; one you never saw can eat a whole day.
3. Don't cut sleep. Sleep is when what you studied gets consolidated. An all-nighter costs you more than it gives.
4. Cut the rereading, not the practice. If something has to go, make it the second pass through your notes.

If you're down to a few days, how to study for an exam in a week has a day-by-day plan that starts from exactly this count.

An example schedule

With the eighteen hours from the economics example and six days until the midterm, one possible split:

• Days 1 and 2: the red and yellow topics, until they make sense. Four hours each.
• Day 3: a first round of practice on everything so far, notes closed. Three hours.
• Day 4: a full past exam under time, then grade it. Three hours.
• Day 5: go back over what went wrong on the practice exam. Two hours.
• Day 6: a short review, mixed questions from every topic, and an early night. Two hours.

It doesn't have to look exactly like this. What matters is that every topic shows up more than once and that the last day is the lightest, not the heaviest.

Frequently asked questions

How many hours a day should I study for an exam?

It depends on how many days you have and how much material is covered, but for most people three or four focused hours kept up over several days work better than one very long day. Work out the total from your material and split it across the days you have left.

How many days before an exam should I start studying?

As early as you can, even with fewer hours a day. A week is enough for most exams if you kept up with the course; if there are topics you never covered, start earlier.

Is it better to study for long hours or in shorter sessions?

Shorter sessions spread over several days. What you study across separate sessions is remembered better than the same material studied in one go, even if the total hours are the same.

Does pulling an all-nighter before an exam help?

Almost never. You show up tired, you perform worse, and what you studied that night consolidates poorly without sleep. A short review and a full night's sleep work better.