Most adults need at least 7 hours of sleep per night. That number comes from both the CDC and the American Academy of Sleep Medicine, which recommend 7 or more hours on a regular basis for optimal health, productivity, and daytime alertness. But the exact amount shifts depending on your age, and the consequences of consistently missing that target are more serious than feeling groggy.
Recommended Sleep by Age
Sleep needs change dramatically from birth through old age. The CDC breaks it down like this:
- Newborns (0–3 months): 14–17 hours
- Infants (4–12 months): 12–16 hours, including naps
- Toddlers (1–2 years): 11–14 hours, including naps
- Preschoolers (3–5 years): 10–13 hours, including naps
- School-age children (6–12 years): 9–12 hours
- Teens (13–17 years): 8–10 hours
- Adults (18–60 years): 7 or more hours
- Adults (61–64 years): 7–9 hours
- Adults (65 and older): 7–8 hours
Notice that the range narrows as you age. A teenager genuinely needs up to 10 hours, and that’s biology, not laziness. For most adults, the sweet spot falls between 7 and 9 hours. Once you’re over 65, the upper end drops slightly to 8 hours.
Why 7 Hours Is the Floor, Not the Goal
Seven hours is the minimum for adults, not the ideal. Your brain cycles through distinct phases of sleep roughly every 80 to 100 minutes, moving from light sleep into deep sleep and then into REM (dream) sleep before starting over. In a typical night, you complete four to six of these cycles. Deep sleep dominates the earlier cycles, while REM sleep gets longer toward morning. Cut your night short and you disproportionately lose that late-morning REM time, which plays a key role in memory, emotional processing, and learning.
This is why there’s a meaningful difference between 6 hours and 7.5 hours. At 6 hours, you’re likely completing only four cycles. At 7.5 to 8 hours, you get five or more, with longer stretches of REM in those final rounds.
What Happens When You Sleep Too Little
Skimping on sleep does more than make you tired. A systematic review found that short sleep duration is associated with a 45% increased risk of coronary heart disease. Insulin sensitivity drops, weight tends to creep up, and your body’s ability to regulate blood sugar deteriorates. These aren’t effects that require years of terrible sleep to show up. In controlled studies, just a single workweek of restricted sleep (getting 4 to 6 hours a night) was enough to reduce whole-body insulin sensitivity by around 13%.
The cognitive effects are equally striking. After about 16 hours of continuous wakefulness, your brain starts showing measurable lapses in attention. By 26 hours awake, those lapses peak dramatically. But you don’t need to pull an all-nighter to feel the damage. When people are limited to 4 to 6 hours of sleep per night over several days, brief “micro-sleeps” lasting up to 30 seconds start appearing. These are moments where the brain essentially shuts off, and the person often doesn’t realize it happened. People sleeping 8 hours show virtually no attention lapses during the day. As sleep time decreases, both the number and length of those lapses increase in a dose-dependent way.
Weekend Catch-Up Sleep Doesn’t Work
If your strategy is to skimp on sleep during the week and make up for it on Saturday and Sunday, the research is not encouraging. A study published in Current Biology tested exactly this pattern and found that weekend recovery sleep failed to reverse the metabolic damage caused by a week of insufficient sleep. Insulin sensitivity still dropped 9% to 27% during the second week of short sleep, even after a weekend of sleeping as long as participants wanted. Body weight continued to increase, and participants’ internal clocks shifted later, making it harder to fall asleep at a reasonable time on Sunday night.
Perhaps most telling, sleep-tracking data from the study showed that participants didn’t even fully recover their lost sleep over the weekend. They carried leftover sleep debt into the next week, starting the cycle in a worse position than before. The takeaway is straightforward: consistency matters more than occasional long nights.
Too Much Sleep Carries Risks Too
While most people worry about sleeping too little, regularly sleeping 10 or more hours a day is also linked to health problems. A large prospective study from the Canadian Longitudinal Study on Aging found that people sleeping 10 or more hours daily had an 83% increase in mortality compared to those sleeping normal amounts. This doesn’t mean a lazy Sunday will hurt you. It means that consistently needing 10-plus hours to feel rested could signal an underlying condition like sleep apnea, depression, or another disorder worth investigating.
How to Tell If You’re Getting Enough
Hours in bed aren’t always the same as hours of actual sleep. A more practical way to gauge whether you’re sleeping enough is to pay attention to how you feel during the day. Clinicians use a tool called the Epworth Sleepiness Scale, which scores your likelihood of dozing off in everyday situations like reading, watching TV, or sitting in traffic. Scores range from 0 to 24. Anything from 0 to 10 is considered normal daytime sleepiness. A score of 11 or higher suggests excessive sleepiness, with 16 to 24 indicating a severe problem.
You can take a simplified version of this assessment yourself. Ask how likely you are to fall asleep during calm, passive activities in the middle of the day. If the honest answer is “very likely,” your sleep quantity or quality probably needs attention, regardless of what the clock says.
Some other reliable signals that you’re not getting enough: you need an alarm to wake up every single morning, you feel noticeably worse on weekdays than weekends, you fall asleep within minutes of your head hitting the pillow (this actually suggests sleep deprivation, not good sleep), or you find yourself losing focus during routine tasks. A well-rested person typically takes 10 to 20 minutes to fall asleep and can sit through a meeting without fighting to keep their eyes open.
Practical Ways to Hit Your Target
Knowing you need 7 to 9 hours and actually getting them are different problems. The single most effective change is keeping a consistent sleep and wake time, even on weekends. Your body’s internal clock relies on regularity. Shifting your wake time by two or three hours on Saturday morning creates a kind of social jet lag that makes Sunday night insomnia almost inevitable.
Light exposure is the other major lever. Bright light in the morning (ideally sunlight within an hour of waking) helps set your internal clock earlier, making it easier to feel sleepy at a reasonable hour. Conversely, bright screens and overhead lights in the last hour or two before bed push that clock later. The effect is real and measurable: evening light exposure delays the release of your body’s natural sleep-promoting signals.
If you’re currently sleeping 5 or 6 hours and want to reach 7, shift your bedtime earlier by 15 to 20 minutes every few days rather than trying to jump straight to an 8-hour schedule. Lying in bed unable to sleep for an extra hour tends to create anxiety around bedtime, which makes the problem worse. Gradual shifts give your body time to adjust.