The Takeaway

  • Although there is some genetic variation, most adults need between 7.5 to 8.5 hours of sleep per 24-hour period to function optimally.
  • You can find your optimal sleep time if you set aside several days (perhaps during a vacation) to allow yourself to sleep as long as possible.
  • Once you know how much sleep you need, it's important to allot that amount of time in your daily schedule for sleep.

How Much Is Enough?

Picture of a clock
An individual’s preference for rising early or sleeping late is largely influenced by genetics. © 2008 JuniperImages Corporation

The amount of sleep that a healthy individual needs is largely determined by two factors: genetics and age. Genetics plays a role in both the amount of sleep a person needs, as well as his or her preference for waking up early (these are the so-called "larks," or morning-type individuals) or staying up late (these are the "owls," or evening-type people). Our internal biological clock, which regulates the cycling of many functions including the sleep/wake cycle, can vary slightly from individual to individual. Although our internal clock is set to approximately 24 hours, if your clock runs faster than 24 hours, you tend to be a "lark" and wake up early; if your clock runs more slowly, you tend to be an "owl" and go to bed later.

The majority of healthy adults require at least 7 hours per 24-hour period.1 This is true from young adulthood through late in life, though many older people have difficulty sleeping in a single block of time each night. Generally, sleep needs during a 24-hour period follow this pattern:

  • Newborns (1 to 3 months)*
  • Infants (4 to 12 months) – 12 to 16 hours
  • Toddlers (1 to 2 years) – 11 to 14 hours
  • Preschoolers (3 to 5 years) – 10 to 13 hours
  • School-aged children (6 to 12 years) – 9 to 11 hours
  • Adolescents (13 to 18 years) – 8 to 10 hours
  • Adults (18 years to the end of life) – at least 7 hours 1,2

*Recommendations for infants younger than 4 months are not included due to the wide range of normal variation in duration and patterns of sleep, and insufficient evidence for associations with health outcomes.2

Even without considering genetics and age, the National Sleep Foundation's 2008 Sleep in America poll found that many adults are apparently not meeting their sleep needs, sleeping an average of only 6 hours and 40 minutes during the week, and about 7.5 hours on the weekends.3 How can you tell if your sleep is adequate and meets your needs? Sleep scientists and physicians have a variety of methods to help determine if you are getting enough sleep.

Dr. Lawrence Epstein discusses ways to determine individual sleep needs.

Pay Attention to Your Sleepiness

Picture of man sleeping on train
Falling asleep during the day is a likely sign that you are not getting adequate sleep. © 2001-2008 HAAP Media Ltd, a subsidiary of Jupiterimages

Sleep needs and patterns of sleep and wakefulness are not the same for everyone. The first step in determining your need for sleep is through self-evaluation. Ask yourself: "How tired do I feel during the daytime? When do I feel most alert? When does fatigue set in?" Even moments of sleepiness that you may think of as routine, for instance, falling asleep on the subway on the way to work, or during a lecture, are likely a sign that you are not getting enough sleep.

Paying attention to your body's cues for sleep is the first step toward figuring out if you are meeting your sleep needs, or if you are sleep deprived or suffering from a sleep disorder (or possibly both).

Keep a Sleep Diary

A very helpful tool to track your sleep time and patterns is a sleep diary. Used in sleep research and clinical settings, a sleep diary is a handy reference to help people become familiar with their own natural patterns of sleep and wakefulness. The information that you will record in the sleep diary is simple and straightforward. It includes the time you go to bed, the time you wake up, your total hours of sleep, and whether you had any nighttime awakenings (and if so, how long you were awake) and any daytime naps. In addition, noting how you feel upon awakening (refreshed or tired), and how you feel at different times of the day will enable you to become more aware of your patterns, and help you determine if you are getting adequate sleep. Just keeping track of your sleep in this way may help improve your situation. If you need more help to improve your sleep, refer to Adopt Good Sleep Habits and Address Your Sleep Issues.

Follow this link to print out a Sleep Diary [PDF].

Take a Sleep Vacation

Another method for determining your sleep need is to take a "sleep vacation." During a two-week period, when you have a flexible schedule or perhaps are on vacation, pick a consistent bedtime and do not use an alarm clock to wake up. Chances are that for the first few days or week you will sleep longer because you'll be paying off your "sleep debt"—the amount of sleep deprivation that you've accumulated over a period of time. If you continue going to bed at the same time and allowing your body to wake up naturally, you will eventually establish a pattern of sleeping essentially the same amount of time each night, probably in the range of 7 to 9 hours. Congratulations! You've identified the amount of sleep that you need.

Make Sleep a Priority

Children crossing the street
Making sleep a priority improves overall health and judgment, as well as the safety of others. © Andersen Ross/Blend Images/Corbis

Now that you know how much sleep you need—and if you've allowed your body to pay back your sleep debt and "find" its natural sleep patterns and duration—you are probably also feeling a lot better, sharper, happier, and healthier. This is how it feels to be well rested. The next step is to make sure that you continue to make sleep a priority and find ways to protect your sleep time.

If You're Having Problems with Sleep

You may be doing all the right things—respecting your sleep needs and patterns, setting aside an ample amount of time to sleep, keeping a sleep diary—but still experiencing daytime sleepiness, fatigue, or insomnia. If that's the case, you should consider consulting a sleep specialist who can help you set up a better sleep environment, provide support for making behavioral changes that may be interfering with sleep, or possibly diagnose a sleep disorder. You have a right to feel well rested—and there are many resources available to help you get the sleep you need.


  1. Watson NF, Badr MS, Belenky G et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. J Clin Sleep Med. 2015; 11:59102.
  2. Paruthi S, Brooks LJ, D'Ambrosio C et al. Recommended Amount of Sleep for Pediatric Populations: A Consensus Statement of the American Academy of Sleep Medicine. J Clin Sleep Med. 2016; 12:785-786.
  3. National Sleep Foundation. 2008 Sleep in America Poll.