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

Counting back six 90 minute cycles plus about 15 minutes to fall asleep puts bedtime near 8:45pm, and five cycles puts it near 10:15pm. Enter your own wake time above for the exact options.

How long is a sleep cycle?

About 90 minutes on average, though real cycles range from roughly 70 to 120 minutes and change through the night. That variation is why cycle-based times are estimates.

Is it better to sleep 6 hours or 7 hours?

Six hours is four complete cycles and seven often lands mid-cycle, so six can feel better on waking. Over weeks, though, total sleep matters more, and most adults need seven to nine hours.

Why do I wake up tired after eight hours?

Often sleep inertia from waking mid-cycle, but poor sleep quality, an irregular schedule, alcohol, or a late large meal all fragment sleep. If it persists despite good habits, it is worth raising with a doctor.

Sleep calculator

Work backwards from your alarm, or forwards from bedtime, in whole sleep cycles.

Runs in your browser. Nothing is sent, saved, or shared.

What do you know?

I need to wake up at

Time to fall asleep

min

Most people take 10 to 20 minutes.

Go to bed at one of these

21:45
6 cycles, 9 hr of sleep
Recommended
23:15
5 cycles, 7 hr 30 min of sleep
Recommended
00:45
4 cycles, 6 hr of sleep
02:15
3 cycles, 4 hr 30 min of sleep

Cycles average 90 minutes but really run from about 70 to 120, and they lengthen toward morning. Later times on this list are rougher estimates than earlier ones.

An alarm clock on a bedside table in morning light

Why cycles and not hours

Sleep runs in repeating cycles of light sleep, deep sleep, and REM, averaging about 90 minutes each. Waking at the end of a cycle, in light sleep, generally feels easier than being pulled out of the deep stage in the middle of one.

This is why six hours can leave you sharper than seven. Six is four clean cycles. Seven lands you mid-cycle, and the grogginess afterwards has a name: sleep inertia.

The 90 minutes is an average, not a clock

Real cycles run from roughly 70 to 120 minutes and vary within a single night, usually lengthening toward morning as REM takes a larger share. So the times here are approximations that get looser the further into the night they go.

Being honest about it: the fourth cycle boundary is a much rougher estimate than the first. Use these as targets to aim near rather than exact moments.

Falling asleep takes time too

Most people need 10 to 20 minutes to drop off, which is why the calculator adds a buffer before the first cycle starts. Going to bed at the calculated time and expecting to be unconscious instantly will put every cycle out by a quarter of an hour.

If you regularly fall asleep in under five minutes, that is usually a sign of sleep deprivation rather than a talent.

Consistency beats optimisation

Cycle timing is a small effect next to regularity. The same bedtime and wake time every day, weekends included, does more for how you feel than landing perfectly on a cycle boundary.

The cost of that consistency is real, and worth naming: it means giving up most of the late nights. Most people would rather have the late nights, which is a reasonable choice as long as it is a choice.

How to use a sleep cycle calculator

1
Choose a direction
Either you know when you must wake up, or you know when you are going to bed. The tool works both ways.
2
Enter the fixed time
Your alarm time, or the time you plan to be in bed with the lights off.
3
Adjust the time to fall asleep
Fifteen minutes is the default. Raise it if you know you take longer to drop off.
4
Pick a cycle count
Five or six cycles suits most adults, which is seven and a half to nine hours. Four is a short night, not a plan.

Questions people ask

What time should I go to bed to wake up at 6am?: Counting back six 90 minute cycles plus about 15 minutes to fall asleep puts bedtime near 8:45pm, and five cycles puts it near 10:15pm. Enter your own wake time above for the exact options.
How long is a sleep cycle?: About 90 minutes on average, though real cycles range from roughly 70 to 120 minutes and change through the night. That variation is why cycle-based times are estimates.
Is it better to sleep 6 hours or 7 hours?: Six hours is four complete cycles and seven often lands mid-cycle, so six can feel better on waking. Over weeks, though, total sleep matters more, and most adults need seven to nine hours.
Why do I wake up tired after eight hours?: Often sleep inertia from waking mid-cycle, but poor sleep quality, an irregular schedule, alcohol, or a late large meal all fragment sleep. If it persists despite good habits, it is worth raising with a doctor.