Zz
Sleep Calculator
When to go to bed or set the alarm so you wake between 90-minute sleep cycles.
Result…
How it's calculated
Bedtime = wake time − cycles × 90 min − time to fall asleep Wake time = bedtime + time to fall asleep + cycles × 90 min
Sleep runs in cycles of light, deep and REM sleep, each about an hour and a half; waking at the end of a cycle rather than in the middle of deep sleep leaves you less groggy. Cycle length varies between people and through the night, so treat the times as a guide. Most adults need seven to nine hours.
Your numbers, step by step
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