Find the best times to wake up or go to sleep based on natural 90-minute sleep cycles. Waking up at the end of a sleep cycle helps you feel refreshed, alert, and energized instead of groggy.
When you fall asleep, your brain goes through distinct repeating neurological phases. A single standard biological sleep cycle lasts approximately 90 minutes on average.
Waking up in the middle of deep sleep (Phase 3 or 4) leaves you feeling tired and groggy (sleep inertia), even if you slept for a long time. Conversely, waking up right at the completion of a full 90-minute loop allows you to wake up naturally energized.
Note: It takes the average human adult about 14 minutes to fall completely into deep sleep, which is factored automatically into our calculation algorithms.