Find the ideal times to sleep or wake up based on natural 90-minute sleep cycles.
Sleep is organized into repeating cycles, each lasting about 90 minutes. Each cycle moves through light sleep, deep sleep, and REM. Waking up mid-cycle can leave you groggy even after a full night. Waking at the end of a cycle tends to feel natural and refreshed.
Most adults need 5 to 6 complete cycles, which equals 7.5 to 9 hours of sleep. The calculator adds 14 minutes for the average time it takes to fall asleep.
Keeping a consistent sleep schedule is one of the most effective ways to improve sleep quality. Aim to go to bed and wake up at the same time every day, even on weekends.