Sleep duration The number of hours of sleep a person needs for optimal health changes throughout life. For example, children ages three to five need anywhere from 10 to 13 hours of sleep each night, whereas adults require 7 to 9 hours. (more) How Much Sleep Do You Need? Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Mar. 4, 2026 •History Sleep is a biological necessity, and sleep needs change throughout life. Newborns may need as many as 17 hours of sleep each day, whereas adults generally need 7 to 9 hours. The necessary amount of sleep for each individual is determined by multiple factors, including internal circadian clock, lifestyle, stress levels, and genetics. Health experts agree that the optimal amount of sleep depends on age and developmental needs. Below is a snapshot of typical recommendations....

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