Should you sleep or revise for one more hour?

The short answer

If you are choosing between a few more hours of revision and a proper night's sleep, choose sleep. NHS guidance on exam stress says cramming all night is usually a bad idea, and that sleep will help more than a few hours of panicky last-minute study. ^[1]

An extra 30 to 60 minutes is a closer call. It depends on what you would do with it, how much sleep you can still get, and when you need to be up. The questions below can help you weigh it up. They are practical suggestions, not a formula tested in research.

Why sleep matters for an exam

Sleep after learning helps memories settle in. Researchers call this consolidation: while you sleep, the brain appears to strengthen and reorganise what you took in during the day. ^[2]

Sleep before a demanding day matters too. In one brain imaging study, people who had missed a night's sleep were worse at forming new memories the next day than people who had slept. ^[4]

Going without sleep also affects attention. A review of sleep deprivation studies found the largest effects on simple attention, with lapses where people briefly lose focus, and clear effects on working memory, the mental space you use to hold information while you work with it. Reasoning was less affected in those studies. ^[3]

Those studies mostly looked at a full night or more without sleep, not an hour less. They show why protecting sleep is sensible, not exactly what one hour costs.

How to decide tonight

Ask yourself three questions before you carry on.

If you do one more hour, make it count

Choose a task with an end point. Testing yourself, such as answering a few practice questions or writing down what you remember about a topic without notes, is a more useful kind of study than rereading or highlighting. ^[5]

Set an alarm for when you will stop, and stick to it. When it goes off, write down one thing to look at in the morning if there is time, then start winding down.

1. Pick one topic you already know reasonably well.
2. Test yourself on it for a fixed time, without notes.
3. Check your answers and note one thing to glance at tomorrow.
4. Stop at the alarm and start getting ready for bed.

What about an all-nighter?

Staying up all night is the option most likely to backfire. After a night without sleep, attention lapses become more common and forming new memories gets harder. ^{[3] [4]}

In one small study, college students who had been awake for 24 hours did worse on a critical thinking test than students who had slept, yet rated their own concentration, effort, and performance higher. A later, larger study found people could still roughly judge their performance after sleep loss, so the evidence here is mixed. Either way, feeling fine is not a reliable sign that you are. ^{[6] [7]}

If you are so far behind that an all-nighter feels like the only option, it may be worth telling a teacher, tutor, or someone at home. That is a sign the workload needs looking at, not a failure on your part.

If you are already short of sleep

Try not to panic about one bad night. In a study of college chemistry students, sleep over the week and month before a test was linked to their marks, but sleep on the single night before was not. That was a correlation in one class, so it does not prove one night never matters, but it does suggest the pattern over time counts for more. ^[8]

If you cannot sleep, you do not have to force it. Our night-before guide has ideas for winding down and what to do if you are lying awake.

In the morning, eat something if you can, give yourself extra time to get there, and read each question carefully. If you feel unwell during the exam, tell the person supervising.

What to do the night before an exam

A 14-day revision timetable with room for rest