What Time Should You Go to Bed?

If you need to wake up at 6:00 AM, you should go to bed at 10:15 PM for five full sleep cycles, or 8:45 PM for six. The trick is not a fixed bedtime — it is counting back in 90-minute sleep cycles from your wake-up time, then allowing about 15 minutes to fall asleep. Waking at the end of a cycle feels far easier than waking in the middle of one.

That one idea explains why you can sleep for eight hours and still wake up groggy, while a shorter night sometimes leaves you feeling fine. Sleep is not one long block of rest. It runs in repeating cycles, and where you wake up inside a cycle matters as much as how long you slept. In this guide you will learn how the cycles work, how to find your own ideal bedtime for any wake-up time, and what to do when a perfect schedule is not possible.

How Sleep Cycles Work

A single sleep cycle lasts roughly 90 minutes and passes through four stages. Light sleep comes first, then deeper sleep, then REM (rapid eye movement) sleep, where most dreaming happens. A healthy adult goes through four to six of these cycles each night. You briefly wake between cycles — usually so briefly you do not remember it — and then start the next one.

The key insight is that waking up during deep sleep feels terrible. That heavy, confused, half-awake feeling even has a name: sleep inertia. It can last 15 to 30 minutes, and on a bad morning it can feel like you never slept at all. Waking up during light sleep or at the end of a cycle, on the other hand, feels much more natural, even after fewer total hours.

This is why the 90-minute rule is so useful. If you time your bedtime so that your alarm lands at a cycle boundary, you wake up in light sleep instead of deep sleep. You are not cheating your body out of rest — you are simply choosing where the alarm falls.

Your Ideal Bedtime, by Wake-Up Time

To find your bedtime, start at your wake-up time and count back in 90-minute steps. Then subtract about 15 minutes for the time it takes the average person to fall asleep. The table below does the math for the most common wake-up times. Five cycles (7.5 hours of sleep) suits most adults; six cycles (9 hours) is the better target if you are catching up on rest or you are regularly tired.

Take the 6:00 AM row as an example. Five cycles back from 6:00 AM is 10:30 PM, and subtracting 15 minutes to fall asleep gives a bedtime of 10:15 PM. Six cycles gives 9:00 PM minus 15 minutes, or 8:45 PM. If 10:15 PM is already in the past — say it is 11:00 PM and you are still awake — the next cycle boundary is 11:45 PM (four cycles). Going to bed at 11:45 PM will usually leave you feeling better at 6:00 AM than going to bed at 11:15 PM, even though you sleep for less time, because you wake at a cycle boundary instead of in the middle of deep sleep.

Want your exact bedtime for an unusual wake-up time, like 5:40 AM? Use the free Sleep Calculator — enter your wake-up time and it works out the best bedtimes for you in seconds.

How Many Hours of Sleep Do You Actually Need?

Most adults need between 7 and 9 hours a night, which is four to six full cycles plus the time to fall asleep. But the right number varies. Teenagers need 8 to 10 hours. Older adults often need slightly less, around 7 to 8 hours. And some people genuinely function well on 7 hours while others need a full 9.

The best test is simple: if you wake up a few minutes before your alarm most days and feel alert through the afternoon without caffeine, you are getting enough. If you need an alarm every morning, feel drowsy by mid-afternoon, or crash on weekends by sleeping two extra hours, your body is telling you it wants more sleep. Weekend lie-ins are not laziness — they are your body repaying a sleep debt.

Is 6 Hours of Sleep Enough?

Short answer: for most people, no — not as a habit. Six hours is four full cycles, which is better than six and a half hours that ends mid-cycle, but it is still below the recommended range for adults. A few nights of six hours will not harm you, and a cycle-timed six hours beats a poorly timed seven. But over weeks, regularly sleeping six hours is linked to poorer concentration, slower reaction times, and weaker immune function.

Think of it this way: cycle timing is a way to make the sleep you get work better, not a replacement for getting enough of it. Use the 4-cycle bedtime when you have a late night you cannot avoid. Do not plan your whole week around it.

Why You Still Feel Tired After 8 Hours

If you sleep eight hours and still wake up exhausted, one of three things is usually going on. First, your alarm may be landing in deep sleep — try shifting your bedtime by 30 minutes either way and see if mornings improve. Second, your sleep quality may be poor: snoring, a room that is too warm, or late caffeine can break your cycles without you fully waking. Third, your sleep schedule may be inconsistent. Sleeping from 11 PM to 7 AM on weekdays and 2 AM to 10 AM on weekends gives your body jet lag every Monday, even though the total hours are the same.

Consistency matters more than most people expect. Your body runs on a circadian rhythm — an internal clock that expects sleep at roughly the same time each night. Keeping your bedtime and wake-up time within about an hour, even on weekends, is one of the highest-impact changes you can make.

Napping Rules That Actually Work

A nap can rescue a bad day or ruin your night, and the difference is length. Keep naps to 20 minutes or less and you stay in light sleep, waking up refreshed. Go past 30 minutes and you sink into deep sleep, waking up groggy — the same sleep inertia problem, just in miniature. The one exception is a full 90-minute nap, which completes a whole cycle and works well on days when you have the time.

Timing matters too. Nap before 3:00 PM if you can. A late-afternoon nap steals sleep pressure from the night, making it harder to fall asleep at your normal bedtime. If you regularly need a nap to get through the day, treat it as a signal: your nighttime sleep probably needs more attention.

How to Fall Asleep on Time

Knowing your bedtime is only half the battle — getting to sleep at it is the other half. A few habits make a real difference. Dim your lights and put your phone down 30 to 60 minutes before bed; bright screens tell your brain it is still daytime. Keep your bedroom cool, dark, and quiet. Avoid caffeine after early afternoon, since it stays in your system for six hours or more. And get some bright light in the morning — sunlight or a bright room within an hour of waking resets your internal clock and makes you sleepy at the right time that evening.

If you lie awake for more than 20 minutes, get up and do something calm in dim light — reading, stretching — until you feel drowsy, then try again. Lying in bed frustrated trains your brain to associate bed with being awake, which makes the next night harder.

The Bottom Line

Stop asking only "how many hours should I sleep?" and start asking "when should my alarm go off in my cycle?" Count back from your wake-up time in 90-minute steps, subtract 15 minutes to fall asleep, and aim for five or six cycles most nights. Keep the schedule consistent, and when a late night is unavoidable, pick the next cycle boundary rather than just going to bed as soon as you can. Try it for a week — most people notice the difference on the very first morning. To get your exact bedtimes, use the free Sleep Calculator.

Frequently Asked Questions

What time should I go to bed if I wake up at 6 AM?

For a 6:00 AM wake-up, go to bed at 10:15 PM for five sleep cycles (7.5 hours) or 8:45 PM for six cycles (9 hours). Both times include about 15 minutes to fall asleep, so your alarm lands at the end of a cycle instead of in the middle of deep sleep.

Is it better to sleep 6 hours or 7.5 hours?

For most adults, 7.5 hours is better because it covers five full sleep cycles and falls inside the recommended 7 to 9 hour range. Six hours is only four cycles and, while better than a poorly timed longer sleep, it leaves most people short on rest if it becomes a habit.

Why do I feel groggy after sleeping 8 hours?

Feeling groggy after eight hours usually means your alarm woke you during deep sleep, your sleep quality was poor, or your sleep schedule is inconsistent. Try shifting your bedtime by 30 minutes so the alarm falls at a cycle boundary, and keep your bedtime and wake-up time steady across the week.

How long should a nap be?

Keep naps to 20 minutes or less to stay in light sleep and wake up refreshed, or take a full 90-minute nap to complete an entire sleep cycle. Avoid naps of 30 to 60 minutes, which wake you from deep sleep and leave you groggy, and try to nap before 3:00 PM so it does not delay your nighttime sleep.