Sleep Cycle Calculator
Find good times to fall asleep or wake up, based on 90-minute sleep cycles.
Tip: Falling asleep usually takes 10 to 20 minutes, so add that time to your bedtime when you plan.
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About this digital tool
A sleep calculator helps you choose when to go to bed or when to wake up, based on sleep cycles of about 90 minutes. Enter a wake-up time and the tool suggests times to fall asleep. Or enter when you lie down and see when you would wake at the end of a cycle. The idea is that waking at the end of a cycle, rather than in the middle of deep sleep, often makes getting up easier. Each option shows the number of cycles and the total hours: five cycles are 7.5 hours and six cycles are 9 hours. Most adults need 7 to 9 hours of sleep. Cycle length varies between people, so treat the times as a practical guide. If you struggle with insomnia or feel sleepy during the day, speak with a doctor.
How to use
- Enter the time you want to wake up, or the time you plan to go to bed.
- Review the suggested times, each shown with its number of cycles.
- Pick the option that fits your schedule and your sleep needs.
Frequently asked questions
Why are sleep cycles about 90 minutes?
Each cycle moves through light sleep, deep sleep and REM sleep, and the whole cycle takes about 90 minutes on average. Waking in the middle of a stage can leave you feeling groggy.
How many hours of sleep do adults need?
Most adults need 7 to 9 hours, which is about four to six cycles. Teenagers usually need 8 to 10 hours and children 9 to 12. Quality matters as much as quantity.
How long should I allow to fall asleep?
Most people fall asleep within 10 to 20 minutes. If it takes much longer, add a few minutes to your bedtime in the calculator.
Can I use this if I have trouble sleeping?
The calculator only helps with timing. If you regularly struggle to fall or stay asleep, or feel tired during the day, speak with a doctor.