Sleep Cycle Calculator
Best times to go to bed or wake up, based on 90-minute sleep cycles.
Result
How to use
- 1
Choose whether you know your wake-up time or your bedtime.
- 2
Pick the time.
- 3
Go to bed or set your alarm at one of the suggested times so you wake between cycles.
Questions
Why 90 minutes?
Sleep runs in cycles of light, deep and REM sleep that last about 90 minutes on average (70–120 minutes in reality). Waking at the end of a cycle usually feels easier than waking from deep sleep.
How much sleep do adults need?
Most adults need 7–9 hours a night — five cycles (7.5 hours) or six cycles (9 hours). Teenagers need 8–10 hours and school children 9–12 hours.
What if I take longer to fall asleep?
Change the “time to fall asleep” setting. The average healthy adult falls asleep in 10–20 minutes.
About this Sleep tool
Sleep Cycle Calculator — Best times to go to bed or wake up, based on 90-minute sleep cycles. It is one of 200 free tools on namasivayam.in, made by software engineer Namasivayam Vadivelan for everyday use in India.
Everything is calculated instantly in your browser: nothing you type or upload is sent to any server, there is no sign-up, and it works on mobile and desktop. Choose whether you know your wake-up time or your bedtime.
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Results are estimates to help you plan. They are not financial, tax or medical advice.