Sleep Calculator
Waking at the end of a 90-minute sleep cycle tends to feel easier than waking in the middle of one. The times below include 15 minutes to fall asleep.
Tips for better sleep
- Keep the same wake time every day, including weekends.
- Get daylight soon after waking to anchor your body clock.
- Avoid caffeine for about 6–8 hours before bed.
- Keep the bedroom cool, dark and quiet.
- Put screens away 30–60 minutes before bed.
Cycle length varies from person to person, so treat the suggested times as a starting point. If you regularly wake up groggy at one time, try the next cycle earlier or later.
Sleep cycles and hours
| Cycles | Time asleep | Good for |
|---|---|---|
| 6 | 9 h | Long rest, recovery |
| 5 | 7 h 30 min | Recommended for most adults |
| 4 | 6 h | A short night |
| 3 | 4 h 30 min | Emergency only |
More time tools
Questions
How long is a sleep cycle?
About 90 minutes on average, though it varies from roughly 70 to 120 minutes between people and through the night.
How much sleep do adults need?
The CDC recommends 7 or more hours a night for adults aged 18 to 60.
Why add 15 minutes?
Most people take 10 to 20 minutes to fall asleep, so the bedtimes leave time to drift off.