How the sleep calculator works
During the night you move through repeating sleep cycles of light sleep, deep sleep and REM sleep. Each cycle lasts about 90 minutes on average. Waking at the end of a cycle, rather than in deep sleep, can make it easier to get up.
Example: to wake at 7:00 AM after 5 cycles of 90 minutes with 15 minutes to fall asleep, go to bed at 11:15 PM (7:00 AM − 7 h 30 m − 15 m).
How much sleep do you need?
| Age group | Age | Recommended sleep |
|---|---|---|
| Newborn | 0–3 months | 14–17 hours |
| Infant | 4–12 months | 12–16 hours (including naps) |
| Toddler | 1–2 years | 11–14 hours (including naps) |
| Preschool | 3–5 years | 10–13 hours (including naps) |
| School age | 6–12 years | 9–12 hours |
| Teen | 13–17 years | 8–10 hours |
| Adult | 18–60 years | 7 or more hours |
| Adult | 61–64 years | 7–9 hours |
| Adult | 65 years and older | 7–8 hours |
Source: Centers for Disease Control and Prevention, based on the American Academy of Sleep Medicine and the National Sleep Foundation.
Frequently asked questions
What time should I go to bed?
Count back from your wake-up time in 90-minute sleep cycles, plus the time it takes you to fall asleep. To wake at 7:00 AM after 5 cycles (7.5 hours) and 15 minutes to fall asleep, go to bed at 11:15 PM.
How long is a sleep cycle?
A sleep cycle through light, deep and REM sleep lasts about 90 minutes on average, though it varies from roughly 70 to 120 minutes between people and through the night. You can change the cycle length in the calculator.
How many hours of sleep do adults need?
The CDC, based on guidance from sleep medicine groups, recommends 7 or more hours a night for adults aged 18 to 60, 7 to 9 hours for ages 61 to 64, and 7 to 8 hours for 65 and older.
Why do I feel groggy even after enough sleep?
Waking in the middle of deep sleep can leave you groggy, a feeling called sleep inertia. Timing your alarm for the end of a cycle may help you wake more easily. If tiredness continues, talk to a doctor.
Is this calculator medical advice?
No. It is a planning tool based on average sleep cycles. People with insomnia, sleep apnea or other sleep problems should speak to a healthcare professional.