Sleep Calculator
Bedtime and wake-up times based on 90-minute cycles
β» A sleep cycle averages 90 minutes but ranges from roughly 70 to 110 minutes between individuals. This is a guide based on waking near a cycle boundary, not a medical tool.
Recommended sleep by age
| Age group | Recommended |
|---|---|
| Newborn (0-3 mo) | 14-17 h |
| Infant (4-11 mo) | 12-15 h |
| Toddler (1-2 y) | 11-14 h |
| Preschool (3-5 y) | 10-13 h |
| School age (6-13 y) | 9-11 h |
| Teen (14-17 y) | 8-10 h |
| Adult (18-64 y) | 7-9 h |
| Older adult (65+) | 7-8 h |
FAQ
Why 90-minute blocks?
Sleep runs in repeating cycles of light sleep, deep sleep and REM, averaging about 90 minutes each. Waking in the middle of deep sleep feels far worse than waking near the end of a cycle, even for the same total hours.
Why add time to fall asleep?
Lying down is not the same as being asleep. Healthy adults usually need 10-20 minutes, so 14 is used as the default. Increase it to 20-30 if you normally take longer to drift off.
How many cycles should I aim for?
Five cycles (7.5 hours) and six cycles (9 hours) are highlighted for adults. Four cycles is on the short side, and three is a fallback for nights when a full sleep is not possible.
It did not make me feel rested
Cycle length varies from roughly 70 to 110 minutes between people and shifts with your condition. Track a few nights to find your own interval. If you sleep enough but stay sleepy through the day, it is worth discussing with a doctor.
Ad (AdSense)