Sleep Smarter.
Wake Refreshed.
Calculate your ideal bedtime using sleep cycle science. Wake up refreshed by timing your sleep to complete full 90-minute cycles.
Sleep Cycle Calculator
What time do you need to wake up?
7:00 AM
Go to bed at...
Sleep stages — 5 cycles
Your night
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Get My Free Sleep TipsHow Sleep Cycles Work
Every night, your body cycles through distinct stages of sleep in roughly 90-minute intervals. A complete cycle moves from light sleep (N1, N2) into deep sleep (N3) and then into REM (rapid eye movement) sleep, where most dreaming occurs.
Waking up at the end of a complete cycle — rather than in the middle of deep sleep — is the key to feeling alert and refreshed. Our calculator times your bedtime so you complete full cycles before your alarm goes off.
Most adults complete 4 to 6 sleep cycles per night. The early cycles are rich in deep sleep (critical for physical recovery), while later cycles contain more REM sleep (essential for memory consolidation and emotional regulation).
The standard 90-minute cycle is an average. Your personal cycle length may be anywhere from 80 to 110 minutes, which is why aligning your wake time to the end of a cycle makes such a noticeable difference in how you feel each morning.
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Medical Disclaimer
The information provided by Sleep Stack is for educational and informational purposes only and is not intended as medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or sleep disorder. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.