Healthy adults need roughly 1.5 to 2 hours of deep sleep and about 1.5 to 2 hours of REM sleep per night, though the exact amounts vary by age and individual. Deep sleep typically accounts for 10% to 20% of your total sleep time, while REM sleep makes up 20% to 25%. For someone sleeping seven to nine hours, that math works out to roughly 90 to 120 minutes of each stage on a good night.
There is no official clinical threshold for exactly how many minutes you need of either stage. What matters more is getting enough total sleep and allowing your body to cycle through all stages naturally.
What Counts as Deep Sleep and REM Sleep
Your brain cycles through four stages of sleep roughly every 90 minutes. The first two stages are light sleep, where your body starts to relax and your heart rate slows. Stage three is deep sleep, also called slow-wave sleep, where brain activity drops to its lowest level and your body does its heaviest repair work. REM sleep is the final stage, characterized by rapid eye movements, vivid dreaming, and a brain that’s nearly as active as when you’re awake.
These stages don’t distribute evenly across the night. You get most of your deep sleep in the first half, during your earliest sleep cycles. REM periods start short (maybe 10 minutes) and grow longer as the night goes on, with the longest stretches happening in the final hours before you wake up. This is why cutting sleep short at either end, whether you go to bed too late or wake up too early, can disproportionately rob you of one stage over another.
Why Deep Sleep Matters
Deep sleep is when your body does its most critical maintenance. Growth hormone release peaks during this stage, driving tissue repair, muscle recovery, and cell regeneration. Your immune system also ramps up protein production that helps fight infection and inflammation.
One of the most important functions happens in your brain’s waste-clearance system, known as the glymphatic system. During deep sleep, the spaces between brain cells physically expand, allowing cerebrospinal fluid to flow more freely and flush out metabolic waste. This includes proteins like amyloid-beta and tau, which are associated with Alzheimer’s disease when they accumulate. The chemical environment shifts too: levels of norepinephrine (a stress-related neurotransmitter) drop, which helps this cleaning process work more efficiently.
People who consistently get too little deep sleep often report feeling physically unrested even after a full night in bed. Brain fog, slower reaction times, and difficulty with learning new physical skills are all tied to insufficient time in this stage.
Why REM Sleep Matters
REM sleep is primarily about your brain rather than your body. This stage plays a central role in consolidating emotional memories, processing difficult experiences, and strengthening learning from the previous day. Research in sleep neuroscience has shown that specific brain wave patterns during REM preferentially consolidate emotional memories over neutral ones, meaning this stage helps your brain prioritize what matters.
REM sleep also appears to function as a kind of emotional regulation system. During this stage, your brain replays and reprocesses stressful or upsetting experiences from waking life, potentially stripping away some of their emotional intensity. This is one reason a good night’s sleep can make a problem feel more manageable in the morning. Dream experiences during REM may help you rehearse coping strategies and create new mental scenarios for dealing with difficult situations.
Chronically low REM sleep is linked to increased emotional reactivity, difficulty with problem-solving, and impaired ability to read social cues.
How These Numbers Change With Age
Babies and young children spend a much larger proportion of their sleep in deep sleep, which makes sense given how rapidly their bodies and brains are developing. As you age, deep sleep naturally declines. By your 60s and 70s, you may spend significantly less than 10% of the night in deep sleep, and some older adults get very little of it. This decline is normal, though it likely contributes to the slower physical recovery and increased cognitive vulnerability that come with aging.
REM sleep is relatively more stable across the lifespan, though newborns spend up to 50% of their sleep in REM compared to the 20% to 25% typical of adults. The general recommendation for total sleep shifts with age too: children aged 6 to 12 need 9 to 12 hours, teenagers need 8 to 10, and adults need 7 to 9 hours.
What Disrupts Your Sleep Stages
Alcohol is one of the most common deep and REM sleep disruptors. It may help you fall asleep faster, but it suppresses REM sleep in the first half of the night and fragments sleep architecture overall. As your body metabolizes the alcohol, you often experience a REM rebound in the second half, leading to vivid dreams and frequent awakenings. The net result is less restorative sleep even if your total hours look fine.
Certain antidepressants, particularly SSRIs and SNRIs, can alter REM sleep patterns. These medications often reduce total REM time or change the muscle-relaxation patterns that normally accompany REM. Cannabis, antihistamines, and some blood pressure medications can also shift the balance between sleep stages.
Stress and anxiety tend to increase lighter sleep at the expense of deep sleep. Sleep apnea repeatedly pulls you out of deeper stages throughout the night, which is why people with untreated apnea can sleep for 8 or 9 hours and still feel exhausted. Irregular sleep schedules, late-night screen use, and caffeine consumed within 6 to 8 hours of bedtime all interfere with normal stage cycling as well.
Your Body Compensates for Lost Stages
If you’ve been deprived of sleep, your brain doesn’t simply pick up where it left off. It prioritizes. After a period of sleep loss, your body will spend more time in deep sleep first, since physical restoration takes precedence. Once that debt is partially repaid, REM sleep rebounds. This REM rebound effect is well documented: after even a few nights of poor sleep, you’ll experience longer and more intense REM periods once you get the chance to sleep fully. This is why people sometimes have unusually vivid or strange dreams after a stretch of bad sleep.
This rebound mechanism is adaptive. Research indicates that increased sleep, especially REM sleep, after stressful periods is an important recovery behavior. Your brain essentially increases its emotional processing time to catch up. The flip side is that chronically cutting your sleep short never gives your body the chance to complete this recovery cycle, and the deficits accumulate.
How to Tell If You’re Getting Enough
Consumer sleep trackers (wrist-worn devices, smart rings, mattress sensors) estimate your sleep stages using movement and heart rate data. These can give you a rough sense of trends over time, but they aren’t nearly as accurate as a clinical sleep study, which measures brain waves directly. If your tracker says you got 45 minutes of deep sleep one night and 90 the next, take the specific numbers with a grain of salt. The general pattern over weeks is more informative than any single night.
Practically, the best indicators that you’re getting enough of each stage are straightforward. If you wake up feeling physically rested, that suggests adequate deep sleep. If you feel emotionally balanced, can concentrate well, and remember new information without unusual difficulty, your REM sleep is likely sufficient. Persistent grogginess despite adequate total sleep hours, on the other hand, often points to disrupted sleep architecture rather than simply not enough time in bed.
The most reliable way to support both stages is consistent total sleep. Going to bed and waking up at roughly the same time every day, sleeping in a cool and dark room, and avoiding alcohol and stimulants in the hours before bed gives your brain the best chance to cycle through all stages in the proportions it needs.