How much deep sleep do you need?

How much deep sleep is normal for adults

Healthy adults typically spend between 10% and 25% of their sleep in deep sleep. That range comes from a review in the Journal of Clinical Sleep Medicine, which says normal subjects spend 10% to 25% of their total sleep time in it. Cleveland Clinic gives a single figure at the top of that range: about 25% of total sleep time in adults. The Sleep Foundation also notes there's no consensus on one number for normal or ideal deep sleep.

In minutes, the two ends of that range work out like this:

Deep sleep in minutes at 10% and 25% of total sleep

Time asleep	At 10%	At 25%
6 hours	36 min	90 min
7 hours	42 min	105 min
8 hours	48 min	120 min
9 hours	54 min	135 min

Say your tracker shows 1 hour of deep sleep after 7 hours asleep. That's about 14%, which sits inside the range.

What deep sleep does

Deep sleep is stage 3 of non-REM (non-rapid eye movement) sleep, the deepest of the stages. NHLBI, part of the National Institutes of Health, says deep sleep is also called slow-wave sleep, after a pattern that shows up in measurements of brain activity. The other main type is REM sleep, when dreaming usually happens.

According to Cleveland Clinic, your body uses deep sleep to repair injuries and strengthen your immune system, and you need it to wake up feeling rested. It's also hard to wake from. Cleveland Clinic says waking during deep sleep can leave you groggy for about 30 minutes.

Why most deep sleep happens early in the night

You usually get more deep sleep early in the night than later. Cleveland Clinic says the body tries to fit in as much stage 3 sleep as it can early on. NHLBI adds that you usually get more REM sleep later in the night. You go through these stages in cycles, usually four to six a night.

So if your tracker's stage chart shows more deep sleep early in the night, that matches what NHLBI describes.

How much deep sleep you need by age

Deep sleep shrinks as you get older. NHLBI says the amount peaks in early childhood, drops sharply in the teenage years and keeps falling through adulthood. Some older people may not have any slow-wave sleep at all. Cleveland Clinic puts it simply: the older you get, the less stage 3 sleep you need.

None of these sources gives a deep sleep target for each age. What changes with age shows up in other ways. MedlinePlus says older adults wake up more often because they spend less time in deep sleep, and they wake an average of 3 or 4 times a night. The CDC recommends 7 or more hours for adults 18 to 60, 7 to 9 hours for ages 61 to 64 and 7 to 8 hours from 65 on.

Can you get more deep sleep?

None of the health sources above names a proven way to raise deep sleep on its own. What they do recommend is enough total sleep and a few habits that help sleep in general. The CDC's list:

• Go to bed and get up at the same time every day.
• Keep your bedroom quiet, relaxing and cool.
• Turn off electronic devices at least 30 minutes before bed.
• Skip large meals and alcohol before bedtime.
• Avoid caffeine in the afternoon and evening.
• Exercise regularly.

On alcohol, MedlinePlus adds that a drink at bedtime can cause you to wake later in the night. If you sleep 7 hours or more and still wake up tired most days, bring it up with a doctor, whatever your tracker says about deep sleep.

How to check your deep sleep in Apple Health

Open the Health app on your iPhone, tap Browse, then Sleep, then Show More Sleep Data and choose Stages. Apple says you'll see the time and percentage you spent Awake or in REM, Core or Deep sleep. The Deep figure is the one to compare with the numbers above. On an Apple Watch, open the Sleep app and turn the Digital Crown.

Treat the deep sleep number as an estimate. In a 2024 study, 35 adults without a sleep disorder each spent one night in a sleep lab wearing three trackers. The Oura Ring's deep sleep was close to the lab test's. A Fitbit counted 15 minutes too little, and an Apple Watch Series 8 counted 43 minutes too little (51 minutes against 94). All three got total sleep about right. The study was small and Oura paid for it, but it shows how far a tracker's deep sleep number can be from a lab measurement.

So a few weeks of nights will tell you more than one. Find your usual range on your own device and watch for nights well outside it. In that study the Oura and the Apple Watch were 44 minutes apart on the same nights. So if you switch trackers, your deep sleep number may change even if your sleep hasn't. If you use an Oura, WHOOP or Garmin, see how to get its sleep into Apple Health so all your nights are in one place.

Sleep Tiles reads the sleep stages your tracker saves to Apple Health and shows them for each night, with stats over 7, 30 or 90 days. Each night's score includes a restfulness part (see how the score is calculated), and habit tags show how much things like caffeine or alcohol move your score.

Common questions

Is 1 hour of deep sleep enough?

On a 7 hour night, 1 hour of deep sleep is about 14% of your sleep. That's inside the 10% to 25% range given in a Journal of Clinical Sleep Medicine review, though below Cleveland Clinic's figure of about 25%. Your tracker's number is also an estimate, so look at your average over a few weeks.

How much deep sleep vs REM sleep should you get?

Cleveland Clinic says each one makes up about 25% of total sleep in adults, and stage 2 sleep takes about 45%. Deep sleep is more common early in the night and REM later, according to NHLBI.

Why does my Apple Watch show so little deep sleep?

One possible reason is that it undercounts. In a 2024 sleep lab study, an Apple Watch Series 8 counted 43 minutes less deep sleep than the lab test did, on average, while getting total sleep about right. The study was small and only one night long, so it's a reason to watch your trend over weeks.

Is it normal to get less deep sleep as you get older?

Yes. NHLBI says slow-wave sleep keeps decreasing through adulthood, and some older people may not have any at all. MedlinePlus says this is one reason older adults wake up more often during the night.

This guide is general information, not medical advice. If poor sleep, snoring, breathing pauses or daytime sleepiness keep going, talk to a doctor.