CALCULATOR 30
Sleep Cycle Calculator
Bedtimes for the time you need to wake, or wake times for when you go to bed, in sleep cycles.
Go to bed at
22:45
Allows about 15 minutes to fall asleep. Cycles vary from person to person, so treat these as a rough guide.
- 21:156 cycles · 9 h7–9 h guidance
- 22:455 cycles · 7.5 h7–9 h guidance
- 00:154 cycles · 6 h
For general information only; not medical advice. Consult a qualified professional before making health decisions.
How this is calculated
Assumptions
One sleep cycle ≈ 90 minutes About 15 minutes to fall asleep
Times
Bedtime = wake time − 15 min − cycles × 90 min Wake time = bedtime + 15 min + cycles × 90 min
Real cycles vary from about 70 to 120 minutes between people and through the night, so treat these as a rough guide. Getting enough total sleep matters more than timing.
Sources
- Carskadon MA, Dement WC, Normal human sleep: an overview. In Kryger MH, Roth T, Dement WC, Principles and Practice of Sleep Medicine.
- Hirshkowitz M et al. (2015), National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health 1:40–43.
About the sleep cycle calculator
How sleep cycles work
Through the night you move through light sleep, deep sleep and REM sleep in cycles of roughly 90 minutes. Waking from light sleep near the end of a cycle usually feels easier than being pulled out of deep sleep, which is the idea behind timing your alarm to whole cycles.
Read more about the Sleep Cycles calculator
How much sleep you need
The US National Sleep Foundation recommends 7–9 hours for adults and 7–8 hours from 65. Five or six cycles (7.5–9 hours) fit that range. A consistent wake time, even at weekends, does more for sleep quality than any calculator.
Frequently asked questions
What time should I go to bed to wake at 6:30?
Around 9:15 pm for six cycles or 10:45 pm for five, allowing 15 minutes to fall asleep.
Is the 90-minute rule accurate?
It's an average. Cycles vary between people and get longer and lighter later in the night, so use it as a starting point.
Is it better to sleep less but wake between cycles?
No. Regularly getting less than 7 hours costs more than any grogginess saved by timing.