Sleep Cycle Calculator
Work out when to go to bed (or when to set your alarm) so you wake up at the end of a sleep cycle instead of in the middle of one.
Go to bed at one of these times (best options first):
9:45 PM
6 sleep cycles · 9.0 h of sleep · recommended
11:15 PM
5 sleep cycles · 7.5 h of sleep
12:45 AM
4 sleep cycles · 6.0 h of sleep
2:15 AM
3 sleep cycles · 4.5 h of sleep
Assumes the average person falls asleep in about 15 minutes and one sleep cycle lasts about 90 minutes. Waking at the end of a cycle feels easier than waking mid-cycle.
Why sleep cycles matter
Sleep moves through repeating cycles of light sleep, deep sleep, and REM, each lasting roughly 90 minutes. Waking at the end of a cycle, when sleep is naturally light, tends to feel easy. Waking mid-cycle, especially during deep sleep, produces the heavy grogginess known as sleep inertia, even after a long night.
How to use the results
Adults need 7 or more hours of sleep, so prefer the 5 or 6 cycle options whenever your schedule allows. The calculator adds 15 minutes for falling asleep, which is the average; if you know you take longer, shift bedtime earlier. Consistency beats precision: keeping the same wake time every day, including weekends, does more for sleep quality than any single perfect night.
Cycle length varies from person to person (roughly 80 to 110 minutes), so treat these times as good starting points, not exact science. This is general information, not medical advice.
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