What Time Should I Go to Bed? Sleep Cycles, Bedtimes, and Wake-Up Times

What time should I go to bed?

If you have ever typed what time should I go to bed into a search bar at midnight, you already know the frustrating part: there is no single bedtime that works for everyone. The right bedtime depends on one thing above all else — the time you have to wake up. Work backwards from your alarm, count in full sleep cycles, and you get a bedtime that is personal and easy to repeat every night.

This guide explains how that maths works, gives you two fully worked examples, and shows how much sleep different age groups generally need. At the end you will find a free tool that does the calculation for you in seconds. One honest note up front: a good bedtime helps you plan your night, but no calculator can promise how you will feel in the morning — sleep quality, stress, light, and health all play a part too.

Start with your wake-up time, not your bedtime

Most people pick a bedtime first — "I will go to bed at 11" — and then set an alarm that cuts their sleep short. That order is backwards. Your wake-up time is usually fixed by work, school, or family life, so it should be the anchor. Once the alarm time is set, subtract whole sleep cycles to find bedtimes that let you wake up at the end of a cycle rather than in the middle of one.

The 90-minute sleep cycle, explained

While you sleep, your brain does not stay in one state all night. It moves through a repeating cycle of stages: light sleep, deeper sleep, and dream-rich REM sleep. One full pass takes about 90 minutes for most adults, and a typical night contains four to six cycles back to back.

Two things to keep in mind. First, 90 minutes is an average: real cycles vary from person to person, roughly between 80 and 110 minutes. Second, falling asleep itself takes time — most people need around 15 minutes after getting into bed — so a good bedtime calculation includes that buffer. The payoff is simple: waking at the boundary between cycles tends to feel easier than being dragged out of deep sleep mid-cycle, which is what causes that heavy, groggy feeling after the alarm.

Worked example 1: you wake up at 6 AM

Say your alarm goes off at 6:00 AM. Counting backwards in 90-minute cycles, and allowing 15 minutes to fall asleep, gives these bedtimes:

For most adults, the 5-cycle option — in bed by 10:15 PM — is the sweet spot: seven and a half hours of sleep, inside the commonly recommended 7 to 9 hours for adults. The 6-cycle option, 8:45 PM, is the better choice if you are catching up after short nights or you simply function better on nine hours. The 4-cycle option, 11:45 PM, gives only six hours and should be an occasional fallback, not a nightly habit.

Notice how the maths works: 6:00 AM minus five cycles (7 hours 30 minutes) is 10:30 PM, and minus the 15-minute buffer gives 10:15 PM. Aim for lights out, phone down, eyes closed by 10:15 — not just getting into bed at 10:15 and scrolling for half an hour.

Worked example 2: you go to bed at 10 PM

Now flip the question. Suppose 10:00 PM is the only bedtime that fits your evening, and you want to know when to set the alarm. Allowing 15 minutes to fall asleep, you would actually start sleeping around 10:15 PM. Counting forward in 90-minute cycles:

If your day allows it, 7:15 AM (six cycles) is the most generous option, and 5:45 AM (five cycles) is the practical one for early risers. The 4:15 AM option is there if you genuinely need to be up before dawn, but six hours night after night is below what most adults need.

How much sleep do you actually need?

Cycle maths tells you when to sleep, but the number of cycles you need depends on your age. The table below gives the widely published general ranges used by sleep health organisations — guidelines for planning, not medical prescriptions.

For adults, that 7–9 hour range maps neatly onto five or six sleep cycles (7.5 or 9 hours). For teenagers, the 8–10 hour range is a reminder that a 6 AM school start with a midnight bedtime is well short of what a growing body and brain needs.

Do not forget the 15 minutes it takes to fall asleep

Almost every bedtime calculation quietly assumes you fall asleep the moment your head touches the pillow. Real life does not work like that. The average healthy adult takes somewhere between 10 and 20 minutes to drift off, so this guide uses 15 minutes as a sensible default.

If you regularly lie awake for much longer than 20 minutes, the answer is not a later bedtime — it is fixing what keeps you awake: bright screens, late caffeine, or a bedroom that is too warm or noisy.

What about naps?

A nap can rescue a bad night, but its length matters as much as a night's bedtime. A 20-minute nap stays inside light sleep and is the safest option for a quick recharge. A 90-minute nap completes one full cycle and can work well on a weekend afternoon. The danger zone is the 30–60 minute nap, which tends to end in deep sleep and leaves you groggier than before. Naps after about 3 PM can also steal sleep pressure from the night ahead.

Five habits that make your bedtime actually work

1. Keep the same wake time, even on weekends. A steady wake time anchors your body clock far more effectively than a steady bedtime alone.
2. Dim the lights an hour before bed. Bright light, especially from screens, tells your brain it is still daytime.
3. Cut caffeine after mid-afternoon. Caffeine has a half-life of around five to six hours, so a 4 PM coffee is still half-active at 10 PM.
4. Cool and darken the bedroom. A slightly cool, dark, quiet room helps you fall asleep faster and stay asleep through the cycles.
5. Treat the bedtime as a deadline, not a suggestion. Set a "wind-down" alarm 30 minutes before bedtime.

Frequently asked questions

What time should I go to bed if I wake up at 7 AM?

Counting back in 90-minute cycles with a 15-minute buffer: 9:45 PM for six cycles (9 hours), 11:15 PM for five cycles (7 hours 30 minutes), or 12:45 AM for four cycles (6 hours). For most adults, 11:15 PM is the practical choice.

Is 6 hours of sleep enough?

For most adults, no — not as a regular pattern. Six hours is four sleep cycles, below the generally recommended 7–9 hours. An occasional short night is normal, but regular six-hour nights are linked with poorer concentration and mood.

What if I go to bed on time but cannot fall asleep?

First check the usual causes: screens in the last hour, caffeine after mid-afternoon, and a room that is too warm or bright. If you regularly lie awake for more than 30 minutes despite good habits, or you snore heavily, talk to a doctor — that is beyond what a bedtime calculator can fix.

Does the 90-minute cycle rule work for everyone?

It works as a planning average. Real cycles vary between roughly 80 and 110 minutes and shift with age and sleep debt, so treat the calculated times as targets, not exact science. If a calculated bedtime consistently leaves you groggy, shift it by 15–20 minutes and see if that feels better.

The bottom line

So, what time should you go to bed? Take your wake-up time, subtract whole 90-minute cycles, subtract 15 minutes to fall asleep, and aim for five or six cycles — 7.5 or 9 hours for most adults. For a 6 AM alarm that means 10:15 PM; for a 10 PM bedtime it means waking at 5:45 AM or 7:15 AM.

If you would rather skip the maths, the free Sleep Calculator does it instantly: enter your wake-up time or bedtime, adjust the fall-asleep time, and it shows your best bedtimes or wake-up times, including a nap mode. Remember, this guide and the calculator are planning aids, not medical advice — if you have ongoing sleep problems, a doctor is the right next step.