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How Much Sleep Do You Need?
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Sleep duration
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.

How Much Sleep Do You Need?

Written by
Kara Rogers
Kara Rogers is the senior editor of biomedical sciences at Encyclopædia Britannica, where she oversees a range of content from medicine and genetics to microorganisms. She joined Britannica in 2006 and...
Kara Rogers
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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
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.

Recommended sleep by age

Health experts agree that the optimal amount of sleep depends on age and developmental needs. Below is a snapshot of typical recommendations. These ranges are based on broad population studies that link sleep duration with physical health, emotional well-being, and cognitive performance.

  • Infants (4–12 months): 12–16 hours
  • Toddlers (1–2 years): 11–14 hours
  • Preschoolers (3–5 years): 10–13 hours
  • Children (6–12 years): 9–12 hours
  • Teens (13–17 years): 8–10 hours
  • Adults (18–64 years): 7–9 hours
  • Older adults (65+ years): 7–8 hours

Research shows that consistently falling short of these amounts can have measurable consequences. For example, adults who regularly sleep less than seven hours are likely to experience cognitive difficulties, such as trouble focusing, reduced reaction times, and poor memory. Other impacts of not obtaining sufficient sleep include emotional instability, marked by heightened stress responses and mood swings; decreased immunity, making it harder to fight infections; and metabolic disruptions with dysregulated appetite, which increase the risk for weight gain. Conversely, too much sleep is potentially linked to underlying health issues, such as depression or chronic inflammation.

Sleep quality

The quality of sleep matters just as much as the quantity. Every night, the body and brain embark on a complex journey of restoration that, when fulfilled, leaves the individual feeling refreshed and able to maintain alertness throughout the day, with steady mood regulation. These benefits are achieved through high-quality sleep, which can be defined as uninterrupted sleep that cycles naturally through the stages the body needs most: light sleep, deep sleep (critical for physical restoration), and REM sleep (rapid eye movement sleep; key for memory and emotional processing).

Fine-tuning sleep

To fine-tune personal sleep needs, individuals can track sleep and daytime energy for a few weeks to notice patterns and then gradually adjust their sleep schedule to accommodate longer, more restorative sleep. Consistency—falling asleep and waking up at roughly the same times daily—and managing lifestyle factors, including caffeine intake and screen time, are additional factors that can affect sleep duration and quality.

Kara Rogers