Sleep
Calculator
Wake up feeling refreshed. By calculating your sleep in 90-minute cycles, you can avoid waking up during deep sleep, which is the primary cause of morning grogginess.
To wake up refreshed at your chosen time, aim to be asleep by:
Calculations include 15 minutes to fall asleep.
The 90-Minute Sleep Cycle
Humans sleep in cycles that typically last about 90 minutes. During these cycles, we move from light sleep to deep sleep and finally to REM (Rapid Eye Movement) sleep. If you wake up in the middle of a cycle (specifically during deep sleep), you’ll feel tired and groggy regardless of how many hours you slept.
How to Use This Tool
Enter the time you need to wake up, and we’ll calculate the best times for you to fall asleep. Each suggested time represents a specific number of completed cycles (typically 4, 5, or 6). Most adults need between 7.5 and 9 hours of sleep to function optimally.