Sleep calculator
What time should you go to bed?
Enter the time you need to get up. The calculator counts back in sleep cycles and shows bedtimes that leave you enough sleep. Or start from your bedtime and see when to set the alarm.
Counts in 90-minute cycles and says where that rule ends · Nothing you enter leaves this page
Your night
Your own estimate. Change it, and every time below moves with it.
Enter a time to see the results.
Other options
How the calculator counts
Three steps. The third is a rule of thumb, so it says so.
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Start from the time that is fixed
Usually that is the alarm: work, school, an early flight. The calculator counts back from it. Starting from your bedtime works the other way round.
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Add the time it takes you to fall asleep
Lying in bed is not sleeping yet. Enter your own number of minutes. Nobody knows it better than you, and every result shifts with it.
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Count in cycles of about 90 minutes
Sleep runs in cycles of light sleep, deep sleep and REM sleep, roughly 90 to 110 minutes each, four to six a night. The calculator uses 90 minutes and shows 6, 5 and 4 cycles, plus 7 hours, the minimum adults need.
Example: to wake at 6:30 a.m. with 15 minutes to fall asleep, five cycles of 90 minutes mean going to bed at 10:45 p.m. For 7 hours of sleep, the latest is 11:15 p.m.
Questions about sleep and bedtimes
What time should I go to bed?
Count back from your alarm: the sleep you need, plus the time you take to fall asleep. Adults need 7 hours or more on a regular basis. With an alarm at 6:30 a.m. and 15 minutes to fall asleep, that means lights out by 11:15 p.m. For five full 90-minute cycles, 10:45 p.m.
How long is a sleep cycle?
Roughly 90 to 110 minutes in adults, with four to six cycles a night. It is not a fixed number. A study that recorded eight healthy adults for about 30 nights each found that sleep varied from night to night, and differed more between people than within the same person. Ninety minutes is a rule of thumb, not a clock.
Will I feel less groggy if I wake up at the end of a cycle?
Maybe, but it is not proven. Some studies find heavier grogginess after waking from deep sleep and others do not, and a review of the research calls the role of deep sleep hard to pin down. Since cycles vary from night to night, no calculator can know where in a cycle your alarm will land. The well-established part is getting enough sleep.
How many hours of sleep do I need?
Adults should sleep 7 hours or more per night on a regular basis, according to a consensus of the American Academy of Sleep Medicine and the Sleep Research Society. That is a floor, not a target: the same statement says more than 9 hours may be right for young adults, for people recovering from sleep debt, and for people who are ill.
What if I take longer than 15 minutes to fall asleep?
Enter your own number; 15 is only where the field starts. If you lie awake for a long time most nights, a calculator can’t fix that, and sleep problems that last are worth raising with a doctor.
Is what I enter sent to WakeYa?
No. The calculation runs in your browser, and nothing you enter is sent anywhere. This page’s security policy does not even allow its scripts to open a connection.
Read more: How much sleep do you need? The number, and how to find your own · Sleeping through your alarm? What actually wakes heavy sleepers
Sources
- Kabrita CS, Ghanem FK, Khalil B: Physiology of Sleep. StatPearls (NCBI Bookshelf)Medical reference text: adult sleep cycles of roughly 90 to 110 minutes, four to six a night.
- Watson NF et al. (2015): Recommended amount of sleep for a healthy adult. SleepConsensus of the American Academy of Sleep Medicine and the Sleep Research Society: 7 hours or more.
- Leguia MG et al. (2025): Variability and predictability in human sleep. Brain CommunicationsEight healthy adults, recorded for a median of 30 nights each: sleep varies from night to night.
- Hilditch CJ, McHill AW (2019): Sleep inertia: current insights. Nature and Science of SleepReview: mixed findings on whether waking from deep sleep makes the morning fog worse.
WakeYa keeps the time you picked
The calculator gives you a bedtime. WakeYa takes care of the morning: at your alarm time it calls you with a voice that keeps talking until you have proven you are awake. There is no snooze button, and wake profiles give work days and weekends their own times. If the AI can’t connect, the classic alarm rings anyway.
