Sleep calculator
Find the best time to go to bed or wake up, based on 90-minute sleep cycles.
How much sleep do you need?
| Age | Recommended per night |
|---|---|
| School age (6–12) | 9–12 hours |
| Teens (13–18) | 8–10 hours |
| Adults (18–64) | 7–9 hours |
| 65 and older | 7–8 hours |
Ranges from the American Academy of Sleep Medicine and the US National Sleep Foundation. This tool is general information, not medical advice.
Need a short rest instead? The nap timer is set for a 20-minute power nap.
Questions people ask
How does the sleep calculator work?
It counts back or forward in 90-minute sleep cycles and adds about 15 minutes to fall asleep. Waking at the end of a cycle, rather than in the middle of deep sleep, usually leaves you feeling less groggy.
How many sleep cycles do I need?
Most adults need 7 to 9 hours of sleep, which is about five or six cycles. Teenagers need 8 to 10 hours.
Is a sleep cycle always 90 minutes?
No. Cycles typically last 80 to 110 minutes and vary between people and through the night, so treat the times as a guide. Change the cycle length or the time to fall asleep if you know yours.