Sleep calculator
Say when you need to get up, or when you’re going to bed, and get times that fit whole sleep cycles of about 90 minutes.
Sealed on this device
Runs in your browser. Nothing is uploaded.
Sealed
Your night
It’s now
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The times follow the clock while this page is open.
Go to bed at
Choose a time to see the suggestions.
Cycles vary from night to night and from one person to another: take these times as a guide, not a rule.
How much sleep is recommended
| Age | Recommended |
|---|---|
| Newborns, 0 to 3 months | 14 to 17 hours |
| Babies, 4 to 11 months | 12 to 15 hours |
| Toddlers, 1 to 2 years | 11 to 14 hours |
| Preschoolers, 3 to 5 years | 10 to 13 hours |
| Children, 6 to 13 years | 9 to 11 hours |
| Teenagers, 14 to 17 years | 8 to 10 hours |
| Adults, 18 to 64 years | 7 to 9 hours |
| Adults, 65 and over | 7 to 8 hours |
Source: National Sleep Foundation (2015). Children’s figures include naps.
Babies and young children have shorter sleep cycles, so the times above are meant for teenagers and adults.
If you often find it hard to fall asleep or stay asleep, or feel tired even after enough sleep, talk to a doctor.
How it works
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Say what you know
Choose the time you need to wake up, the time you plan to go to bed, or “Going to bed now”.
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Set the time
Enter the time. If you know your own rhythm, change how long you take to fall asleep or the length of a cycle.
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Pick a time
Choose between 4, 5 or 6 full cycles. Each suggestion shows how much sleep it gives and how that compares with the recommendation for your age.
Frequently asked questions
How does the sleep calculator work?
Sleep runs in cycles of about 90 minutes. To wake up at a given time, the calculator counts back 4, 5 or 6 full cycles, then the time it takes you to fall asleep. To wake up at 7:00 a.m. with 15 minutes to fall asleep, it suggests going to bed at 9:45 p.m. (9 hours of sleep), 11:15 p.m. (7 hours 30 minutes) or 12:45 a.m. (6 hours). From a bedtime, it counts forward the same way.
How long is a sleep cycle?
About 90 minutes on average, but it varies from about 70 to 120 minutes, from one person to another and over the night. During each cycle you go through light sleep, deep sleep and REM sleep, when most dreams happen, and the REM periods get longer towards the morning (National Institute of Neurological Disorders and Stroke, “Brain Basics: Understanding Sleep”). That’s why you can change the cycle length, and why the results are an estimate.
How much sleep do I need?
The National Sleep Foundation recommends 7 to 9 hours a night for adults aged 18 to 64, 7 to 8 hours from 65, and 8 to 10 hours for teenagers aged 14 to 17. The American Academy of Sleep Medicine (AASM) recommends at least 7 hours a night for adults aged 18 to 60, and 8 to 10 hours for teenagers aged 13 to 18. Needs vary from one person to another: these are ranges, not targets.
Is it better to wake up at the end of a cycle?
Sleep is lighter at the end of a cycle, and waking from deep sleep can leave you groggy for a while. Many people find it easier to get up between cycles, but there is little evidence that timing your alarm to the minute helps. Getting enough sleep, at regular times, matters more. If you often sleep badly or feel tired even after enough sleep, talk to a doctor.
Does it handle daylight saving time?
Yes. The calculator plans the coming night in your device’s time zone. On the night the clocks go forward or back, the times shift so that you still get the same amount of sleep, and a note tells you.
Is anything saved?
No. Everything is calculated in your browser. Your times and settings are not saved, not even on this device, and are never sent anywhere.