Most adults need 7 to 9 hours of sleep per night. That range comes from a large expert review published in Sleep Health, and the CDC reinforces the lower end: at least 7 hours for anyone 18 or older. But the right number for you depends on your age, your genetics, and whether the sleep you’re getting is actually restful.
Recommended Sleep by Age
Sleep needs shift dramatically from birth through old age. Newborns need the most, and the requirement gradually drops until it levels off in adulthood. Here are the current expert recommendations:
- Newborns (0 to 3 months): 14 to 17 hours
- Infants (4 to 11 months): 12 to 15 hours
- Toddlers (1 to 2 years): 11 to 14 hours
- Preschoolers (3 to 5 years): 10 to 13 hours
- School-age children (6 to 13 years): 9 to 11 hours
- Teenagers (14 to 17 years): 8 to 10 hours
- Young adults (18 to 25 years): 7 to 9 hours
- Adults (26 to 64 years): 7 to 9 hours
- Older adults (65 and up): 7 to 8 hours
These are ranges, not single targets. A 30-year-old who feels sharp and energized on 7 hours doesn’t need to force 9. And a teenager who sleeps 8 hours isn’t falling short just because the range goes up to 10. The key is where you land within that window while feeling genuinely rested during the day.
Why Sleep Cycles Matter
Your brain doesn’t sleep in one continuous block. It cycles through light sleep, deep sleep, and REM sleep in a repeating pattern that lasts roughly 80 to 100 minutes per cycle. Over a full night, you typically complete four to six of these cycles.
Deep sleep dominates the early cycles and handles physical repair, immune function, and memory consolidation. REM sleep, where most dreaming happens, takes up a larger share of later cycles. This is why cutting your night short by even one cycle doesn’t just cost you time. It disproportionately cuts into REM sleep, which plays a major role in emotional regulation and learning. Waking up in the middle of a cycle also tends to leave you groggier than waking at the end of one, which is why 7.5 hours of sleep can sometimes feel better than 8.
What Happens When You Sleep Too Little
Sleeping under 7 hours regularly isn’t just about feeling tired. The American Heart Association added sleep duration to its core cardiovascular health metrics in 2022, placing it alongside blood pressure, cholesterol, and physical activity as a vital sign of heart health. Insufficient sleep disrupts how your body processes sugar and stores fat, raising the risk of type 2 diabetes and obesity over time. It also impairs the neural processes involved in attention, decision-making, and emotional control.
The cognitive effects are not subtle. Chronic short sleep is now considered an acquired risk factor for dementia in older adults, alongside conditions like high blood pressure and physical inactivity. For younger adults, the more immediate toll shows up as slower reaction times, worse memory, and a higher likelihood of anxiety and depression. Even people who feel they’ve “adapted” to 5 or 6 hours typically perform worse on objective cognitive tests than they realize.
Can You Catch Up on Weekends?
The idea of sleeping in on Saturday to make up for a rough week is appealing, but research from Harvard suggests it doesn’t work the way most people hope. In one study, subjects who cut their sleep by five hours over the workweek and then slept extra on weekends still showed excess calorie intake after dinner, reduced energy expenditure, increased weight, and harmful changes in how their bodies processed insulin. Their results were similar to subjects who stayed sleep-deprived all weekend without any catch-up sleep at all.
Sleep debt resolved “on paper,” meaning total hours evened out, but the metabolic damage had already been done. The takeaway is straightforward: consistently sleeping enough during the week matters more than compensating on weekends. Even adding 30 minutes to your nightly sleep on weekdays has a bigger payoff than banking on a long Saturday morning.
When Sleeping Too Much Is a Problem
Oversleeping gets less attention than sleep deprivation, but regularly needing more than 9 hours to feel rested can signal an underlying issue. According to Johns Hopkins Medicine, persistent oversleeping is associated with type 2 diabetes, heart disease, obesity, depression, and a greater overall risk of dying from a medical condition. The sleep itself isn’t necessarily causing these problems. Instead, the excessive need for sleep often points to conditions like sleep apnea, thyroid disorders, or depression that are disrupting sleep quality, forcing your body to spend more time in bed to get what it needs.
If you’re sleeping 9 or 10 hours and still waking up tired, the issue is likely not duration but quality. Fragmented sleep from breathing interruptions, restless legs, or frequent waking can mean you’re spending plenty of time in bed without completing enough full sleep cycles to feel restored.
Some People Genuinely Need Less Sleep
There is a small group of people who thrive on just 4 to 6 hours a night. Researchers have identified a condition called familial natural short sleep, traced to mutations in a gene called DEC2 and at least six other genes discovered since. These natural short sleepers don’t just tolerate less sleep. They function normally, show no cognitive decline, and don’t accumulate the health risks associated with sleep deprivation in the general population.
This trait is rare, though no precise population estimate exists. If you sleep 5 hours a night and genuinely feel alert, energetic, and healthy without caffeine propping you up, you may carry one of these variants. But most people who believe they’re fine on minimal sleep are actually running on accumulated debt without recognizing the toll. The honest test: if you sleep longer on vacation or days off when no alarm forces you awake, your body is telling you it needs more than you’re giving it during the week.
How to Find Your Personal Number
The simplest way to determine your ideal sleep duration is to pick a two-week stretch where you can go to bed at a consistent time and wake without an alarm. Most people settle into a natural pattern within a few days once their initial sleep debt clears. The duration you land on, typically somewhere in the 7 to 9 hour range, is your baseline.
Daytime sleepiness is another useful signal. The Epworth Sleepiness Scale, a quick self-assessment used in clinical settings, scores your likelihood of dozing during routine activities like reading, watching TV, or sitting in traffic. Scores range from 0 to 24, and anything under 10 is considered normal. Scoring above 10 suggests your current sleep isn’t meeting your body’s needs, whether because of duration, quality, or both.
Pay attention to how you feel between 1 and 3 p.m., when a natural dip in alertness occurs. A mild energy lull is normal. Struggling to keep your eyes open or relying on caffeine to get through the afternoon is a sign you’re running short. Your ideal sleep duration is the amount that makes that afternoon window feel manageable without stimulants.