Sleep

Sleep calculator: what time to go to bed or wake up

Pick the time you need to wake up, or the time you are going to bed, and get bedtimes or wake-up times that fit 4, 5 or 6 full sleep cycles of about 90 minutes, plus the minutes it takes you to fall asleep. Adults are advised to sleep 7 hours or more, which means 5 or 6 cycles for most people.

I want toTimeYour wake-up time or your bedtime, depending on the choice above.Sleep cyclesMinutes to fall asleepminAbout 15 minutes is typical for good sleepers. Change it if you usually take longer.

11:15 PM

7 to 9 h of sleep

Bedtime for 6 cycles (9 h of sleep)9:45 PM
Bedtime for 5 cycles (7.5 h of sleep)11:15 PM
Bedtime for 4 cycles (6 h of sleep)12:45 AM
Time in bed for your choice, including falling asleep7 h 45 min

7.5 h

The large time is the bedtime for the number of cycles you chose. It counts back from your wake-up time: the minutes you set for falling asleep, then whole cycles of 90 minutes. Real cycles run shorter or longer, so read it as a target, give or take a few minutes.

Within the 7 hours or more advised for adults.

What this means

Five cycles give about 7.5 hours of sleep and 6 cycles give about 9 hours. Both meet the adult recommendation of 7 hours or more per night. Waking at the end of a cycle, when sleep is lighter, is the idea behind the calculator; because real cycles vary, treat the time as a close estimate.

What to do next

If you still wake up groggy, try moving bedtime by 10 to 15 minutes for a few nights, since your own cycles may be a little shorter or longer than 90 minutes. If you sleep this long and still feel unrested most days, mention it to a doctor.

This is general health information, not a diagnosis. Reference ranges vary by laboratory and by person — use the values on your own report and talk to a clinician about what they mean for you.

How the sleep calculator works

Sleep runs in cycles. In each one you pass through light sleep, deep sleep and REM (dreaming) sleep, and the whole sequence averages about 90 minutes in adults, repeating 4 to 6 times a night. The idea behind a cycle calculator is to time your alarm for the end of a cycle, when sleep is lighter. The calculator adds the time it takes you to fall asleep (15 minutes unless you change it) and then counts whole cycles. To wake at 7:00 AM after 5 cycles, you would go to bed at 11:15 PM: 15 minutes to fall asleep plus 7 hours 30 minutes of sleep.

Bedtimes for a 7:00 AM wake-up, with 15 minutes to fall asleep.
Cycles	Sleep	Go to bed at
6 cycles	9 h	9:45 PM
5 cycles	7.5 h	11:15 PM
4 cycles	6 h	12:45 AM

What time should I go to bed?

Find your wake-up time in the left column and read across. Each bedtime already includes 15 minutes to fall asleep. Five cycles (7.5 hours) is the usual sweet spot for adults; 6 cycles (9 hours) suits days when you are catching up on sleep.

Bedtimes by wake-up time, with 15 minutes to fall asleep.
Wake-up time	6 cycles (9 h)	5 cycles (7.5 h)	4 cycles (6 h)
5:00 AM	7:45 PM	9:15 PM	10:45 PM
5:30 AM	8:15 PM	9:45 PM	11:15 PM
6:00 AM	8:45 PM	10:15 PM	11:45 PM
6:30 AM	9:15 PM	10:45 PM	12:15 AM
7:00 AM	9:45 PM	11:15 PM	12:45 AM
7:30 AM	10:15 PM	11:45 PM	1:15 AM
8:00 AM	10:45 PM	12:15 AM	1:45 AM

How long is a sleep cycle, really?

The 90-minute cycle is an average. In a laboratory study of 369 healthy adults and more than 6,000 recorded cycles, the median cycle lasted 96 minutes, cycle length differed a lot from person to person, and the first cycle of the night was consistently shorter than the later ones. Age, sex and how sleep-deprived you are all shift the timing. So the calculator gives you a good first guess. If you keep waking groggy at the suggested time, move bedtime 10 to 15 minutes in either direction for a week and see which feels better.

How many hours of sleep do adults need?

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults sleep 7 or more hours per night on a regular basis. Regularly sleeping less than that is linked with weight gain, diabetes, high blood pressure, heart disease, stroke and depression. More than 9 hours may be appropriate for young adults, people recovering from sleep debt and people who are ill.

Adult sleep duration, from the AASM and Sleep Research Society consensus (2015).
Sleep per night	Cycles of 90 min	What the consensus says
Under 7 hours	4 or fewer	Below the recommendation when it happens regularly
7 to 9 hours	5 to 6	Meets the recommendation of 7 hours or more
Over 9 hours	7 or more	May suit young adults, recovery from sleep debt or illness; otherwise uncertain

Frequently asked questions

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

For 5 sleep cycles (7.5 hours) go to bed at 10:15 PM, and for 6 cycles (9 hours) at 8:45 PM. Both times include 15 minutes to fall asleep. If you need longer to drift off, set your own figure in the calculator.

How long is one sleep cycle?

About 90 minutes on average, and most people go through 4 to 6 cycles a night. Individual cycles vary: a large laboratory study found a median of 96 minutes, with the first cycle of the night shorter than the rest.

Is it better to sleep 6 hours or 7.5 hours?

For adults, 7.5 hours. Six hours is below the 7 hours or more that sleep medicine societies recommend on a regular basis. Timing the alarm to a cycle may make a single short night feel easier; it does not change how much sleep you got.

How long should it take to fall asleep?

Falling asleep within about 15 minutes is considered a sign of good sleep quality. Taking much longer on most nights is one of the things an insomnia questionnaire asks about.

How many sleep cycles do I need?

Most adults need 5 or 6 cycles, which is 7.5 to 9 hours of sleep. Sleep medicine societies recommend 7 hours or more per night for adults, and 4 cycles (6 hours) falls short of that. If you sleep 5 or 6 cycles and still feel tired most days, talk to a doctor.