Sleep Calculator: Best Bedtime or Wake-Up Time in 90-Minute Cycles
Pick the time you need to wake up (or the time you will go to bed) to see times that fit whole 90-minute sleep cycles.
- Nothing you type is stored
- Free
- No signup
Go to bed at
10:45 PM
5 cycles · 7.5 h- For 6 cycles (9 h)
- 9:15 PM
- For 4 cycles (6 h)
- 12:15 AM
An estimate for general information, not medical advice.
Includes 15 minutes to fall asleep.
All options
| Cycles | Bedtime | Hours asleep |
|---|---|---|
| 6 | 9:15 PM | 9 |
| 5 | 10:45 PM | 7.5 |
| 4 | 12:15 AM | 6 |
| 3 | 1:45 AM | 4.5 |
How to use
- Choose "I want to wake up at" or "I go to bed at".
- Enter the time and how long you usually take to fall asleep.
- Pick a bedtime or alarm time from the list; 5–6 cycles suit most adults.
Good to know
Sleep runs in cycles of light, deep and REM sleep, about 90 minutes each on average (real cycles vary from about 70 to 120 minutes). Waking at the end of a cycle, rather than from deep sleep, can leave you feeling less groggy.
Example: to wake at 6:30 AM with 15 minutes to fall asleep, 5 cycles (7.5 hours) means going to bed at 10:45 PM, and 6 cycles (9 hours) at 9:15 PM.
Adults need 7–9 hours a night (National Sleep Foundation; AASM), which is 5–6 cycles; teenagers need 8–10 hours. Cycle timing is a rough guide, so a regular schedule matters more than exact minutes. If you snore loudly, stop breathing at night or feel sleepy every day, see a doctor.
Questions
What time should I sleep to wake up at 6 AM?
With 15 minutes to fall asleep: 10:15 PM for 5 cycles (7.5 h) or 8:45 PM for 6 cycles (9 h).
How long is one sleep cycle?
About 90 minutes on average, but it varies between people and through the night. You can change the cycle length under More options.
Is 4 cycles (6 hours) enough?
Not for most adults on a regular basis. Short sleep is linked with poorer mood, focus and long-term health.
Why add time to fall asleep?
Most people take 10–20 minutes to drift off. Adding it makes the cycle timing line up with when you are actually asleep.
Is my data saved?
No. Everything is calculated on your device.