Sleep Cycle Calculator — Best Time to Wake Up
Calculate the optimal bedtimes and wake-up times based on 90-minute sleep cycles to help you wake up feeling refreshed.
The Science of Sleep Cycles
Have you ever slept for 8 hours but woken up feeling exhausted? This often happens when you are woken up in the middle of a deep sleep stage. Waking up at the end of a sleep cycle helps you feel refreshed and alert.
The 90-Minute Sleep Cycle
Human sleep consists of repeating cycles that last approximately 90 minutes. Each cycle moves through stages of light sleep, deep sleep, and REM (Rapid Eye Movement) sleep. Waking up during light sleep—at the end of a cycle—minimizes sleep grogginess (sleep inertia).
Planning Your Sleep Schedule
This calculator helps you determine bedtimes or wake-up times based on these 90-minute intervals. It factors in an average of 15 minutes to fall asleep after getting into bed. For most adults, aiming for 5 or 6 sleep cycles (7.5 or 9 hours of sleep) is optimal.