Sleep Calculator: What Time to Go to Bed or Wake Up

Sleep Calculator: Best Time to Sleep and Wake Up

Tell it when you need to wake up and it suggests bedtimes that let you wake at the end of a sleep cycle, or pick a bedtime to see good alarm times. You can adjust how long you take to fall asleep and your cycle length, and switch between 12- and 24-hour time.

By Suman Sharma · Updated October 25, 2026

How to use this tool

Choose what you want to know

Pick 'Wake up at' to get bedtimes, 'Go to bed at' to get alarm times, or 'Sleep now' to use the current time.

Enter the time

Set your wake-up time or bedtime. Open 'Adjust for you' if you usually take longer than 15 minutes to fall asleep.

Pick a time

Options with 5 or 6 cycles (7½ to 9 hours) are marked as recommended for most adults.

Example

You need to be up at 7:00 AM.

Input

Mode: Wake up at
Wake-up time: 7:00 AM
Time to fall asleep: 15 min · Cycle length: 90 min

Result

6 cycles (9 h): go to bed at 9:45 PM
5 cycles (7 h 30 min): go to bed at 11:15 PM
4 cycles (6 h): 12:45 AM
3 cycles (4 h 30 min): 2:15 AM

Each option is 90 minutes apart, counted back from 7:00 with 15 minutes added to fall asleep. If you take 30 minutes, every bedtime moves 15 minutes earlier.

How sleep cycles work

Through the night you move through repeating cycles of light sleep, deep sleep and REM sleep. Each cycle lasts about 90 minutes on average, though anywhere from roughly 70 to 120 minutes is normal, and most people go through four to six a night.

Waking up from deep sleep is what leaves you groggy, a feeling called sleep inertia. Timing your alarm for the lighter sleep at the end of a cycle can make getting up easier, even after the same amount of sleep.

How much sleep you need

The American Academy of Sleep Medicine and the Sleep Research Society recommend at least 7 hours a night for adults. Teenagers need more, around 8 to 10 hours. Five cycles is 7½ hours and six is 9, which is why those are the recommended options here.

The limits of a calculator

Cycles aren't identical: early cycles have more deep sleep, later ones more REM, and length varies from person to person and night to night. Treat the times as a good starting point. If you consistently wake up tired after enough hours, or snore heavily, talk to a doctor, since conditions like sleep apnea can't be fixed by timing.

Bedtimes for common wake-up times

Allowing 15 minutes to fall asleep and 90-minute cycles. Times are for 6, 5 and 4 cycles (9, 7½ and 6 hours of sleep).

Wake at 5:00 AM: 7:45 PM, 9:15 PM or 10:45 PM
Wake at 5:30 AM: 8:15 PM, 9:45 PM or 11:15 PM
Wake at 6:00 AM: 8:45 PM, 10:15 PM or 11:45 PM
Wake at 6:30 AM: 9:15 PM, 10:45 PM or 12:15 AM
Wake at 7:00 AM: 9:45 PM, 11:15 PM or 12:45 AM
Wake at 7:30 AM: 10:15 PM, 11:45 PM or 1:15 AM
Wake at 8:00 AM: 10:45 PM, 12:15 AM or 1:45 AM

Habits that make the times work

Keep the same wake-up time every day, weekends included. It anchors your body clock more than bedtime does.
Get daylight soon after waking; it helps you feel sleepy at the right time in the evening.
Stop caffeine 8 or more hours before bed. The caffeine calculator shows how much is left at bedtime.
Keep the bedroom cool, dark and quiet.
If you can't sleep after about 20 minutes, get up and do something calm until you feel sleepy.

Common errors

Forgetting the time it takes to fall asleep

Going to bed at 11:00 isn't falling asleep at 11:00. If you usually lie awake for half an hour, set 30 minutes under 'Adjust for you'.

Using the short options every night

Three or four cycles can get you through one short night, but regularly sleeping 6 hours or less builds up sleep debt. Aim for 5 or 6 cycles most nights.

Getting the 12- and 24-hour times mixed up

Switch the clock to the format you use. 00:45 in 24-hour time is 12:45 AM, a quarter to one in the morning, not lunchtime.

Frequently asked questions

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

With 15 minutes to fall asleep and 90-minute cycles: 8:45 PM for 6 cycles, 10:15 PM for 5 cycles, or 11:45 PM for 4. Enter 6:00 in the calculator to adjust for yourself.

Is it better to sleep 6 or 7 hours?

Adults are advised to sleep at least 7 hours. Six hours is exactly four cycles, so you may wake up more easily than after 7, but over time you'll be short on sleep. Seven and a half hours, five cycles, is a better target.

How long is a sleep cycle?

About 90 minutes on average, but it varies between people and across the night, typically from about 70 to 120 minutes. You can change the cycle length in the calculator.

Does waking up between cycles really help?

Waking from light sleep usually feels better than being pulled out of deep sleep. Cycle lengths vary, so aligning to them is an estimate, but it's a reasonable way to choose between alarm times.

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

With 15 minutes to fall asleep: 11:15 PM for 5 cycles (7½ hours) or 9:45 PM for 6 cycles (9 hours). 12:45 AM gives 4 cycles, but that's only 6 hours.

How long does it take to fall asleep?

Most healthy adults fall asleep in about 10 to 20 minutes. The calculator uses 15 by default; change it if you usually take longer.