How many hours of sleep do you need? Most adults, 7 or more

Most adults need at least 7 hours of sleep a night, on a regular basis. That is the recommendation of the American Academy of Sleep Medicine and the Sleep Research Society, and the National Sleep Foundation gives a range of 7 to 9 hours for most adults.

Seven is a floor, not a target. Some people need eight or nine, and the only way to learn your own number is to notice how you do on different amounts.

How much sleep do adults need?

In 2015 the American Academy of Sleep Medicine and the Sleep Research Society brought together a panel of sleep experts to look at the research and agree on a number. Their answer for adults aged 18 to 60 was 7 or more hours a night, regularly. They linked sleeping less than that, night after night, with a range of health problems, with more errors and with a greater risk of accidents.

The US Centers for Disease Control and Prevention (CDC) sums up the guidance from sleep medicine groups for different ages like this:

Two details matter. These are hours of sleep, not hours in bed, and most people spend a little time awake in bed at each end of the night. And they are about what you get regularly, not on one good night.

What about more? The same expert panel said that sleeping more than 9 hours a night may be right for young adults, for people paying back a stretch of short nights, and for people who are ill. For other adults, they weren't sure whether regularly sleeping that long was good or bad. If you regularly need far more than 9 hours to feel rested, it is worth mentioning to a doctor.

Why sleep needs vary

The ranges exist because people are different.

• Genes. Some people genuinely do well near the bottom of the range and some need the top of it. People who truly thrive on much less than 7 hours exist, but they are rare. Many people who feel fine on five or six have simply got used to being tired.
• Age. Teenagers need more than adults, and their body clocks also run later, which is why early starts are hard for them. Older adults often sleep more lightly and wake more in the night.
• Sleep debt. After a run of short nights, you need more for a while.
• Illness, pregnancy and hard training. All of these can raise how much sleep you need.
• Sleep quality. Eight hours broken by a snoring partner, a hot room or a bladder that wakes you twice is not the same as eight unbroken ones.

How do you know if you're not getting enough sleep?

You can't always feel it directly. People who have been short of sleep for weeks often stop noticing how tired they are, even as their attention and mood slide. These are the more reliable signs:

• You need an alarm every day and usually hit snooze.
• You sleep much longer on days off than on workdays.
• You feel heavy and slow after lunch, and fight to stay awake in meetings.
• You get through the afternoon on coffee.
• You doze off within minutes of sitting down in the evening, on the couch, at a movie or on a train.
• You are shorter-tempered and more forgetful than usual.
• You feel drowsy when you drive. If that happens, pull over somewhere safe and rest. A drowsy driver is a danger to everyone on the road.

One or two of these on a bad week is normal. Most of them, most weeks, means you are probably running short.

How to find your own number

The recommendations give you a range. Your own number is somewhere inside it, and you can get a rough idea of where.

Try the vacation test

On a week or two off, with no alarm and no late nights, go to bed when you feel sleepy and get up when you wake on your own. The first few nights you may sleep long, paying back debt. After that, your sleep usually settles to a steady length. That length is a fair guide to what you need.

Keep a simple sleep diary

For two weeks, write down roughly when you went to bed, when you woke and how you felt at 3 PM, on a scale of one to five. Patterns show up fast: the nights that lead to clear afternoons tend to share a length.

Use what you already have

If you use an iPhone, the Health app can show your sleep, from your iPhone's sleep schedule or from an Apple Watch if you wear one to bed. Treat the minutes as an estimate, since a wrist device can only infer when you are asleep. The trend over weeks is more useful than any single night.

How do you protect sleep when work runs late?

Late finishes are where sleep usually goes. A few habits keep a busy week from turning into a short-sleep week.

Fix the wake time, then count back

You can't make yourself fall asleep, but you can choose when you get up. Pick a wake time you can keep most days, then count back about 8 hours to get a bedtime that leaves room for 7 or more hours of actual sleep. If you get up at 6:30, that means being in bed around 10:30. What time should you go to bed? has a table for other wake times. Keeping that wake time steady, weekends included, makes the bedtime easier to keep, as Why a consistent bedtime matters explains.

Stop work an hour before bed

Work that runs right up to bedtime keeps your head busy long after the laptop closes. Pick a time to stop, write tomorrow's list so it is out of your head, and close the lid. How to stop working late on your Mac has steps that make the stop stick, from a shutdown routine to Screen Time.

Let your Mac draw the line

A couple of Apple's own settings help:

• Downtime. In System Settings > Screen Time > Downtime you can set a nightly schedule during which only the apps you allow are available.
• A Focus at night. In System Settings > Focus you can add a schedule to a Focus such as Do Not Disturb, so notifications go quiet at bedtime. If you use a sleep schedule on your iPhone, its Sleep Focus can carry over to the Mac when Share across devices is on.

Pay back a short night gently

After a late one, resist sleeping in late, which pushes your body clock later. Get up within an hour or so of your usual time, get some daylight, and go to bed a little earlier the next night. A short nap early in the afternoon can help in between.

A nudge before the hours go

Notchpals can't count your hours. It doesn't track sleep and has no idea when you dropped off. Where it helps is the evening, which is usually where the hours go. Its Sleep characters know one thing about your night, the bedtime you set (11 PM unless you change it), and if Nod the koala is in your crew, Nod comes out of your Mac's notch in the hour before it, as long as you are still working.

NodBedtime's coming. Last call for emails. Wrap it up, nice and easy.

Keep working and Nod tries again once bedtime has passed, and once more if you are still at it in the small hours. Press Done and Nod says goodnight. If you have already left the desk, none of it happens: the crew only visits while you are at the Mac.

When it is more than hours

Sometimes the problem isn't time in bed. If you regularly get 7 hours or more and still wake exhausted, if someone has noticed you snore loudly or seem to stop breathing in your sleep, if you struggle to fall or stay asleep most nights, or if you nod off during the day without meaning to, talk to a doctor. Sleep problems are common and many of them can be helped, but they need someone who can look at the whole picture.