How Much Deep Sleep Do You Need, and How to Get More

There is no official target for deep sleep, but in healthy young adults it typically makes up roughly a fifth of the night, which works out to well over an hour in 7 to 9 hours of sleep, and the amount falls steadily with age. Deep sleep, also called slow-wave sleep or N3, is the stage when your brain waves are slowest and you are hardest to wake. It is linked to physical recovery, growth hormone release, memory and clearing waste from the brain. You cannot force more of it, but sleeping long enough, moving during the day, and cutting late caffeine and alcohol all help. This guide explains how much deep sleep you need, how it differs from REM sleep, and how to get more.

It is educational, not medical advice.

Key Takeaways

• Deep sleep declines with age: in 149 healthy men, deep slow-wave sleep fell from about 18.9% of the night at age 16 to 25 to about 3.4% at age 36 to 50 (Van Cauter et al., 2000).
• The trend holds across studies: a meta-analysis found the percentage of slow-wave sleep falls with age in adults (Ohayon et al., 2004).
• Exercise helps: a single bout of exercise had a small beneficial effect on slow-wave sleep in a meta-analysis of 66 studies (Kredlow et al., 2015).
• Caffeine reduces it: caffeine typically reduced slow-wave sleep and slow-wave brain activity in a systematic review (Clark and Landolt, 2017).
• Alcohol is a false friend: it can increase deep sleep early in the night but disrupts sleep in the second half (Ebrahim et al., 2013).

What Is Deep Sleep?

Sleep cycles through stages several times a night. Light sleep (stages N1 and N2) takes up most of the night, deep sleep (N3, or slow-wave sleep) comes mostly in the first few hours, and REM sleep, when most vivid dreaming happens, gets longer toward morning. In deep sleep, brain waves become large and slow, breathing and heart rate settle, and it is hard to wake up; if you are woken from it, you often feel groggy for a while.

Our guide to the stages of sleep explains how deep sleep fits alongside N1, N2 and REM sleep in each cycle of the night.

How Much Deep Sleep Do You Need?

No health body sets an exact number of minutes, and the right amount depends on your age. What studies do show is how much healthy people usually get. In a combined analysis of 149 healthy men, deep slow-wave sleep made up about 18.9% of the night in early adulthood and about 3.4% in midlife, with lighter sleep taking its place (Van Cauter et al., 2000). A meta-analysis of sleep studies from childhood to old age confirmed that the percentage of slow-wave sleep falls as adults get older (Ohayon et al., 2004).

Group (from one study of healthy men)	Deep sleep share of the night	About how much in 7.5 hours of sleep
Age 16 to 25	About 19%	About 85 minutes
Age 36 to 50	About 3%	About 15 minutes

These figures come from men only, and individual numbers vary widely, so use them only as a rough guide. The best everyday test is simple: if you wake feeling reasonably refreshed and function well during the day, you are probably getting enough.

If you regularly fall short, the missed hours add up; our guide to sleep debt explains what research shows about catching up.

For total sleep rather than deep sleep alone, see our guide how much sleep do I need, with recommended hours by age.

Can You Trust Your Sleep Tracker?

Rings, watches and apps estimate sleep stages from movement and heart rate rather than brain waves, so their deep sleep numbers are estimates. They are useful for spotting trends, such as less deep sleep after late drinks, but a low number on one night is not a reason to worry. Only a lab sleep study measures stages directly.

Trackers also report REM sleep; our guide to how to increase REM sleep explains how much you need.

What Does Deep Sleep Do?

• Physical recovery and hormones: deep sleep is closely tied to the release of growth hormone, and the age-related fall in slow-wave sleep was accompanied by lower growth hormone secretion (Van Cauter et al., 2000).
• Memory: the slow oscillations of deep sleep help consolidate memories. In one study, gentle sounds timed to these slow waves boosted them and improved next-day memory (Ngo et al., 2013).
• Clearing waste: in mice, sleep increased the space between brain cells by about 60% and sped up the clearance of waste products, including beta-amyloid (Xie et al., 2013).

An alarm that goes off during deep sleep is one reason mornings can feel groggy; our guide to how to wake up when you are tired explains why and what helps.

Deep Sleep vs REM Sleep

REM sleep is not deep sleep. Deep sleep (N3) is the slow-wave stage concentrated in the first half of the night, when the body is most still and hardest to wake. REM sleep comes in longer stretches toward morning, the brain is very active, most vivid dreams happen, and the muscles are temporarily relaxed. Both matter, and a full night of sleep is the only reliable way to get enough of each. Many trackers label stages as light (or core), deep and REM.

Long or late daytime naps can make it harder to sleep at night; our guide to how long a nap should be explains why 10 to 20 minutes in the early afternoon works best for most people.

How to Get More Deep Sleep

1. Sleep long enough, on a regular schedule

Deep sleep comes early in the night, but a regular schedule with enough total sleep protects every stage. Keep the same wake time every day; our morning routine checklist shows how.

2. Exercise during the day

In a meta-analysis of 66 studies, a single session of exercise had small beneficial effects on total sleep time, time to fall asleep, sleep efficiency and slow-wave sleep, and regular exercise improved sleep quality (Kredlow et al., 2015).

3. Cut caffeine earlier

Caffeine typically lengthened the time to fall asleep, shortened sleep and reduced slow-wave sleep and slow-wave brain activity in a systematic review, and older adults may be more sensitive (Clark and Landolt, 2017). Stop by early afternoon.

4. Go easy on alcohol at night

Alcohol consistently increases slow-wave sleep in the first half of the night, but it delays REM sleep and disrupts sleep in the second half (Ebrahim et al., 2013). The net result is worse sleep, not better.

5. Keep the bedroom cool, dark and quiet

Fewer disturbances mean fewer interruptions to deep sleep. Blackout curtains, a cool room and earplugs or steady background noise all help.

6. Wind down before bed

A warm shower 1 to 2 hours before bed, dim lights and screens away all help you fall asleep sooner; see our guide to how to fall asleep fast for the research behind each step.

7. Be cautious with "deep sleep" products

Sound devices that time gentle noise to slow brain waves are an active research area, but the technique used in studies is precise lab equipment, not ordinary background noise. Supplements marketed for deep sleep vary widely; our guides to magnesium glycinate for sleep and sleep supplements without melatonin review what human trials show.

If you need rest during the day without a nap, our guide to non-sleep deep rest (NSDR) covers a guided relaxation practice you can do while staying awake.

Why Am I Not Getting Deep Sleep?

Common reasons include short or irregular sleep, late caffeine, alcohol in the evening, a warm or noisy bedroom, stress, and simply getting older. Some medical conditions and medicines can also reduce it, which is why persistent poor sleep is worth discussing with a doctor.

If you keep waking in the early hours, see our guide on why you wake up at 3am.

Where Our Products Fit

Our Melatonin Nasal Spray provides 200 mcg of melatonin with L-theanine per serving as part of a bedtime routine, and our Theanine Nasal Spray provides 36 mg of L-theanine per two-spray serving for calm evenings. Follow the directions on the label. Our sleep health guide and our guide on how to sleep better cover sleep quality in more depth, and L-theanine for sleep explains what the research shows.

When to See a Doctor

Safety note: talk to a doctor if you wake unrefreshed most mornings despite enough time in bed, snore loudly or stop breathing during sleep, feel very sleepy during the day, or have had poor sleep for more than a few weeks. These can point to conditions such as sleep apnea, insomnia or restless legs syndrome, which a sleep study can assess. Do not drive if you feel drowsy. Check with your doctor before starting a sleep supplement if you are pregnant, breastfeeding or taking medication.

Sources

• Van Cauter E et al. Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men. JAMA, 2000. PubMed
• Ohayon MM et al. Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan. Sleep, 2004. PubMed
• Kredlow MA et al. The effects of physical activity on sleep: a meta-analytic review. Journal of Behavioral Medicine, 2015. PubMed
• Clark I et al. Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep Medicine Reviews, 2017. PubMed
• Ebrahim IO et al. Alcohol and sleep I: effects on normal sleep. Alcoholism, Clinical and Experimental Research, 2013. PubMed
• Ngo HV et al. Auditory closed-loop stimulation of the sleep slow oscillation enhances memory. Neuron, 2013. PubMed
• Xie L et al. Sleep drives metabolite clearance from the adult brain. Science, 2013. PubMed

Frequently Asked Questions

How much deep sleep should I get a night?

There is no official target. In one study of healthy men, deep sleep was about 19% of the night in young adults and about 3% in midlife, so the amount depends heavily on age.

How many hours of deep sleep do you need?

Most adults get well under two hours, and often under one hour after early adulthood. Feeling refreshed during the day matters more than an exact number.

Is REM sleep the same as deep sleep?

No. Deep sleep is slow-wave sleep, mostly early in the night. REM sleep is when most dreaming happens and comes mostly later in the night.

How can I increase deep sleep naturally?

Sleep enough on a regular schedule, exercise during the day, stop caffeine by early afternoon, limit evening alcohol and keep the bedroom cool, dark and quiet.

Why am I not getting deep sleep?

Short or irregular sleep, late caffeine, evening alcohol, a disruptive bedroom, stress and age are the most common reasons. Persistent problems are worth checking with a doctor.

Does alcohol help deep sleep?

It can increase deep sleep early in the night, but it disrupts sleep later in the night, so overall sleep is worse.

Are sleep tracker deep sleep numbers accurate?

They are estimates based on movement and heart rate. They are useful for trends, but only a lab sleep study measures sleep stages directly.

What happens if you don't get enough deep sleep?

You may wake unrefreshed and feel tired during the day. Deep sleep is linked to physical recovery, growth hormone release and memory.

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.