How it works
Sleep runs in cycles that are often approximated as about 90 minutes. This tool counts back 4, 5 or 6 cycles from your wake time and adds about 14 minutes to fall asleep. It is a rule of thumb, not medical advice. The CDC recommends that adults aged 18–60 get 7 or more hours per night.
Source for the 7+ hour guideline: CDC, "About Sleep".
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Frequently asked questions
How many hours of sleep do adults need?
The CDC recommends 7 or more hours a night for adults aged 18–60.
Why 90 minutes?
It is a common average cycle length; real cycles vary from person to person and through the night.