Sleep Cycle Calculator
Find the best time to sleep or wake up
You should try to fall asleep at:
Note: Each sleep cycle lasts ~90 minutes.
We've factored in 15 minutes to fall asleep.
How Sleep Cycles Work
Human sleep is not a uniform state of rest. Instead, it consists of multiple cycles that last approximately 90 minutes each. During these 90 minutes, your brain cycles through several stages of sleep, moving from light sleep to deep sleep, into REM (Rapid Eye Movement) sleep, and back again. Waking up in the middle of a deep sleep phase often leads to grogginess and sleep inertia, while waking up at the end of a cycle leaves you feeling refreshed and alert.
Frequently Asked Questions
Why 90 minutes?
Scientific studies have shown that the average human brain takes about 90 to 110 minutes to complete one full progression through all the stages of non-REM and REM sleep. Structuring your sleep around these 90-minute blocks aligns your wake time with your body's natural biological rhythms.
How many cycles are ideal?
Most healthy adults need about 5 to 6 sleep cycles per night to feel fully rested. Five cycles equal 7.5 hours of sleep, while six cycles equal 9 hours. Our calculator highlights these specific cycle marks as optimal targets.