Find optimal bed or wake times based on 90-minute sleep cycles
Recommended Bedtimes
About Sleep Cycles
Each sleep cycle lasts approximately 90 minutes. Waking at the end of a cycle (rather than in the middle) may help you feel more refreshed, but real cycles vary from about 70 to 120 minutes between people and across the night, so treat the times as a rule of thumb. Adults are advised to sleep at least 7 hours per night (5 cycles = 7.5 h, 6 cycles = 9 h). An average of 15 minutes to fall asleep is factored in. Persistent sleep problems, loud snoring or daytime sleepiness are worth discussing with a doctor.
What This Means For You
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Frequently Asked Questions
A typical sleep cycle is about 90 minutes. Waking at the end of a cycle (rather than mid-cycle) leaves you feeling more rested. The calculator works back from your desired wake time in 90-minute increments.
Most adults need 5-6 complete cycles per night (7.5-9 hours). Teenagers need 8-10 hours; young children need 10-13 hours including naps.
7.5 hours is better. It contains a full extra cycle of deep and REM sleep. Six hours consistently is linked to memory issues, weight gain, and weakened immunity over time.