Is Six Hours of Sleep Enough? Adults Need Seven, and Feeling Fine Is No Proof

Seven hours is the floor for adults. The American Academy of Sleep Medicine and the Sleep Research Society set that number in a joint consensus statement in 2015, and CDC uses the same line for everyone from 18 to 60.

If you get 6 and feel more or less fine, you have plenty of company. The answers below cover where the line comes from, why your own sense of tiredness is a weak guide, and what does and doesn’t make up the difference.

How many hours of sleep does an adult need?

You need at least 7 hours a night as an adult, and the main U.S. guidelines agree on that number.

CDC lists 7 or more hours for ages 18 to 60, then 7 to 9 hours for ages 61 to 64 and 7 to 8 hours from 65 on. The National Sleep Foundation’s 2015 recommendations, written by an 18-member panel that reviewed 312 studies, use similar bands and add a wider range for people whose needs run a little high or low.

Age	Recommended	May be appropriate for some
18 to 25	7 to 9 hours	6 to 11 hours
26 to 64	7 to 9 hours	6 to 10 hours
65 and older	7 to 8 hours	5 to 9 hours

National Sleep Foundation, 2015. The panel drew on studies published between 2004 and 2014.

Plan your nights around the middle column. The wider column allows a 20-year-old anywhere from 6 to 11 hours and a 40-year-old from 6 to 10. It covers people whose bodies need a little more or less, and a busy schedule doesn’t put you in that group.

Can you sleep too much?

Sleeping more than 9 hours can be normal for some adults, and the 2015 consensus statement names young adults, people recovering from sleep debt and people who are ill.

For everyone else, the statement calls the evidence uncertain. If you’ve started needing far more sleep for no clear reason, mention it at your next checkup.

Is six hours of sleep enough?

Six hours a night falls short of the adult minimum, and after the first few days it stops feeling short.

The clearest evidence comes from a 2003 study in the journal Sleep led by Hans Van Dongen at the University of Pennsylvania. His team kept 48 healthy adults aged 21 to 38 in a lab and gave them 4, 6 or 8 hours in bed each night for 14 days, while another group stayed awake for 3 days straight. Each day the volunteers took a reaction-time test that counts lapses, the moments when attention drops out.

An older Black woman with short silver-grey curly hair, in a deep teal cardigan over a cream blouse, pours tea from a speckled cream teapot at a sunlit wooden kitchen table, with a bowl of peaches in front of her and plants on the windowsill. — *By day 14 of the 2003 study, the 6-hour and 4-hour groups both reported feeling only slightly sleepy.*

By the end of two weeks, the 6-hour group was lapsing nearly as often as people who had gone a full night without sleep. Their sleepiness ratings rose in the first days and then barely moved while their test scores kept sliding.

So feeling fine tells you little after months of 6-hour nights. Your sense of how sleepy you are is the very measure that stopped tracking performance in that lab.

Do older adults need less sleep?

You still need 7 to 8 hours a night after 65, according to both CDC and the National Sleep Foundation.

What changes with age is the shape of your night. The National Institute on Aging notes that older people tend to go to bed earlier and get up earlier, and many find their sleep lighter and more broken than it used to be. The National Sleep Foundation’s wider range for this group runs from 5 to 9 hours, the only adult band that dips below 6.

If you’re over 65, your age group hits the target more often than any other. In CDC’s 2014 survey data, 73.7 percent of them reported 7 hours or more, the highest share of any age group.

Going to bed early isn’t the same as sleeping too little. If you’re asleep by 9:30 p.m. and up at 5 a.m., you’ve had 7.5 hours.

How many adults don’t get enough sleep?

About a third of American adults sleep less than 7 hours, according to CDC’s analysis of 2014 survey data from 444,306 people in every state and the District of Columbia.

In that survey, 11.8 percent reported 5 hours or less and 23.0 percent reported 6 hours, which puts 34.8 percent in the short group. Six hours was the most common short answer. To see which group you’re in, add up the hours you actually slept over the last seven nights and divide by 7.

Adults reporting at least 7 hours of sleep in the lowest and highest states and nationally, CDC analysis of 2014 survey data, adjusted for age. CDC found the lowest shares clustered in the Southeast and along the Appalachian Mountains.

Hawaii had the lowest share at 56.1 percent and South Dakota the highest at 71.6, a gap of 15.5 points against a national figure of 64.9 percent. Even in South Dakota, more than a quarter of adults fell short, and a well-rested state says nothing about your own nights.

Why do I wake up at 3 a.m.?

You’ve usually just reached the lighter part of your night, after most of your deep sleep is done.

Your sleep runs in cycles of about 90 minutes, four to six of them on a good night. Deep sleep fills more of your early cycles, and REM periods grow longer toward morning. By 3 a.m., a noise, a warm room or a full bladder has an easier time waking you.

On most nights you fall back asleep within minutes and won’t remember waking. Loud snoring with gasping or pauses, which a partner usually hears before you do, is worth raising with a clinician, and so is daytime sleepiness that lasts even after a few weeks of full nights.

Does a nap count toward my sleep total?

A nap adds sleep to your day, but the 7-hour floor in the 2015 consensus statement is written for the sleep you get at night.

A short nap can still help you. In a NASA study of long-haul airline pilots from the mid-1990s, crews given a 40-minute rest window during the cruise portion of a flight fell asleep in about 6 minutes and slept about 26. They stayed more alert through descent and landing than crews who didn’t rest.

If you need a nap every day just to get by, your nights are usually running short. The National Institute on Aging suggests skipping naps in the late afternoon or evening, since they can keep you awake at night.

Can I catch up on sleep over the weekend?

A Saturday lie-in wins back some lost sleep, but in a 2019 study in Current Biology it didn’t undo what a short week did to the body.

An older Black woman with short silver-grey curly hair, in loose peach pajamas, sleeps on her side under a rumpled sage and white quilt in a honey-wood bed, with late-morning sun coming through sheer curtains, a deep teal wall behind her and a cup and a book on the nightstand. — *The weekend group ate less after dinner on its two free days, and the late snacking came back once the 5-hour nights resumed.*

A University of Colorado Boulder team led by Christopher Depner kept 36 healthy adults aged 18 to 39 in a lab for two weeks. It compared 9-hour nights, 5-hour nights, and 5-hour weekdays broken by a weekend of unlimited sleep.

The weekend sleepers gained only 66 minutes of extra sleep. Both short-sleep groups snacked after dinner and gained weight. Insulin sensitivity, a measure of how well the body handles blood sugar, fell 13 percent in the group held to 5 hours and 9 to 27 percent in the weekend group.

The weekend group’s body clocks also shifted later on Sunday night, which can make it harder to fall asleep. For about one extra hour, that’s a poor trade.

Six hours a night comes to 42 hours a week, 7 short of the floor’s 49 and far more than the hour a lie-in won back. Moving your bedtime 30 minutes earlier on five weeknights wins back 2.5 of those hours.

If a sleep problem is new, severe or lasting, see a clinician.