To sleep well before an exam, stop studying about an hour before bed, go to bed at a time that gives you 7.5 hours of sleep, and don't pull an all-nighter. Just as important: one rough night before a test is less damaging than you'd fear. Your sleep over the week and month before tends to matter more than the night before.
Free toolSleep CalculatorBest bedtime or wake-up time, based on 90-minute sleep cycles.Why the whole week matters more than one night
In a study of 88 college chemistry students who wore sleep trackers all semester, better sleep quality, longer sleep and more consistent sleep were all linked to better grades. Sleep measures accounted for nearly a quarter of the difference in performance.
The surprise: sleep on the single night before a test wasn't linked to scores. Sleep over the week and month beforehand was.
That's good news on two counts. If you're anxious and sleep badly the night before, it probably won't sink you. And the most useful thing you can do for exam season is start sleeping well a week or more out, not just the night before.
What bedtime to aim for
Work back from when you need to be up. These bedtimes include 15 minutes to fall asleep and end on a full 90-minute sleep cycle, so you're more likely to wake at a light point.
| Wake-up time | 5 cycles (7.5 h) | 6 cycles (9 h) |
|---|---|---|
| 6:00 AM | 10:15 PM | 8:45 PM |
| 6:30 AM | 10:45 PM | 9:15 PM |
| 7:00 AM | 11:15 PM | 9:45 PM |
| 7:30 AM | 11:45 PM | 10:15 PM |
| 8:00 AM | 12:15 AM | 10:45 PM |
Five cycles is a solid target for most adults. Leave enough time to wake up properly, eat, and get to the exam without rushing. For any other time, use the sleep calculator.
Don't pull an all-nighter
Sleep is when your brain does a lot of the work of stabilizing what you learned during the day. Cramming all night trades that away for a few extra hours of tired, low-quality studying.
Staying awake also hits your thinking hard. In a classic study, performance after 17 hours awake was comparable to having a blood alcohol level of 0.05%, and after 24 hours it was comparable to 0.10%, over the US legal driving limit. That's not the state you want to sit a three-hour exam in.
If it's already too late and you've been up all night, read how to recover from an all-nighter.
The night-before plan
- Stop studying about an hour before bed. A last skim of your summary sheet is fine. Learning new material at midnight mostly raises your stress.
- Pack everything first. ID, pens, calculator, water, charger. One less thing to worry about in the dark.
- Set two alarms. Knowing you have a backup makes it easier to stop checking the time.
- Dim the lights and put your phone away. Group chats about "what's going to be on it" are a sleep killer.
- Write down what's bugging you. A quick list of worries or last-minute topics gets them out of your head.
- Go to bed at your usual time, not dramatically earlier. Going to bed two hours early usually just means lying awake.
Watch your caffeine
Caffeine is a study staple, but it lingers. Here's how much of one 95 mg cup of coffee is still in your system at bedtime, assuming the average 5-hour half-life:
| Coffee this many hours before bed | Caffeine still in you |
|---|---|
| 8 hours | about 31 mg |
| 6 hours | about 41 mg |
| 4 hours | about 55 mg |
| 2 hours | about 72 mg |
A single cup takes almost 10 hours to drop below 25 mg. Energy drinks and double shots take longer. Check your own cutoff with the caffeine calculator.
If you can't fall asleep
It happens to almost everyone before a big exam. Try not to fight it.
- Rest counts for something. Lying quietly in the dark is more restful than scrolling.
- If you've been awake a long while, get up, sit somewhere dim, and do something calm until you feel sleepy. More tips in lying in bed awake.
- Remind yourself that one short night is unlikely to make or break your result, especially if you've slept reasonably well in the days before.
Exam morning
- Get up at your planned time, even if you slept badly.
- Get some daylight and eat something you're used to.
- Have your usual caffeine, not double. Now isn't the time to find out how an extra energy drink affects your nerves.
Exam season as a whole
If you have a run of exams, protect a steady schedule across the whole stretch. Aim for 7 to 9 hours most nights, keep a consistent wake-up time, and treat sleep as part of your revision plan. For more on student sleep, see how much sleep college students need.