Most adults need at least 7 hours of sleep per night. The exact number shifts with age, ranging from as much as 17 hours for newborns down to 7 or 8 hours for older adults. These ranges come from the CDC and align with the National Sleep Foundation’s expert consensus, which has remained consistent through 2025.
Sleep Needs by Age
Your sleep requirement drops steadily from birth through adulthood, then levels off. Here are the current recommended ranges:
- 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
- Teenagers (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 adult recommendation doesn’t cap at a hard number. It says “7 or more,” which for most people means 7 to 9 hours is the sweet spot. People who consistently sleep within that range are significantly more likely to report thriving overall, with one large survey finding 66% of them flourishing compared to 57% of those sleeping outside that window.
Why Some People Claim They Need Less
You’ve probably met someone who insists they function perfectly on 5 hours. A genuine short-sleep gene does exist. Mutations in two specific genes can allow people to feel fully rested on 4 to 6 hours without any health consequences. But this trait is extraordinarily rare. Researchers have identified only about 50 families worldwide who carry these mutations. For everyone else, consistently sleeping under 7 hours comes with real costs, even if you feel like you’ve adapted to it.
The tricky part is that your brain loses the ability to accurately judge its own impairment when you’re sleep-deprived. You stop noticing how much slower or foggier you’ve become, which is why so many people genuinely believe they’re fine on too little sleep.
What Happens When You Don’t Get Enough
Sleep deprivation doesn’t just make you tired. It impairs your thinking in ways that are measurable and surprisingly severe. Staying awake for 17 hours produces cognitive impairment equivalent to a blood alcohol concentration of 0.05%. Push that to 24 hours without sleep, and your impairment matches a BAC of 0.10%, which is above the legal driving limit in every U.S. state.
The metabolic effects are just as concrete. One study restricted healthy men to 5 hours of sleep per night for a single week and measured a 20% drop in insulin sensitivity, the body’s ability to regulate blood sugar effectively. Glucose tolerance also declined. These are the same metabolic changes that precede type 2 diabetes, and they showed up after just seven nights of short sleep.
The Risks of Sleeping Too Much
Sleeping more isn’t always better. Consistently logging more than 9 hours per night is associated with health problems, not just a lack of them. In one large study tracking participants over about 8 years, people who combined excessive daytime sleepiness with long sleep duration (over 9 hours) had an 83% higher rate of heart attack compared to people who slept a normal amount and didn’t experience daytime sleepiness.
That said, long sleep is often a symptom rather than a cause. People sleeping excessively tend to have higher rates of obesity, inflammation, sleep disorders, and chronic illness. If you’re regularly sleeping 10 or more hours and still feel tired, that pattern itself is worth paying attention to, because it usually signals something else going on.
Can You Catch Up on Weekends?
The idea of “catching up” on sleep over the weekend is partially true, but only within limits. A recent study found that for people averaging under about 7.3 hours on weeknights, sleeping 1 to 2 extra hours on weekends improved their body’s ability to process blood sugar. That’s a meaningful metabolic benefit.
Here’s the catch: sleeping more than 2 extra hours on weekends actually reversed the benefit. The relationship followed an inverted U-shape, where moderate weekend recovery helped, but oversleeping on weekends made metabolic markers worse, even for people who were sleep-deprived during the week. The takeaway is that a little weekend catch-up can soften the blow of a rough week, but it’s not a substitute for consistent sleep.
Sleep Needs for Athletes and Active People
If you exercise intensely or play competitive sports, you likely need more than the standard 7 to 9 hours. Research on basketball players found that sleep deprivation cut shooting accuracy by as much as 50%, while extending sleep to 10 or more hours improved accuracy by about 10%. That’s a potential 60% swing in performance based on sleep alone.
Athletes recovering from hard training sessions rely heavily on deep sleep for tissue repair and hormone regulation. If you’re training seriously, aiming for 8 to 10 hours is reasonable, and the gains aren’t just physical. Reaction time, decision-making, and injury risk all improve with adequate sleep.
How to Tell If You’re Getting Enough
The simplest test: if you need an alarm clock every morning and feel groggy for the first hour after waking, you’re probably not sleeping enough. Another useful signal is what happens on days with no obligations. If you sleep significantly longer when you don’t set an alarm, that gap represents your accumulated sleep debt.
For a more structured check, the Epworth Sleepiness Scale is a quick self-assessment used by sleep specialists. You rate your likelihood of dozing off in eight everyday situations (reading, watching TV, sitting in traffic) on a scale of 0 to 3. A total score of 0 to 10 is normal. Scores of 11 to 14 suggest mild excessive sleepiness, 15 to 17 indicate moderate sleepiness, and 18 or higher points to severe sleepiness that warrants evaluation. You can find the questionnaire through Harvard’s Division of Sleep Medicine.
Naps: Helpful or Harmful?
A short nap can genuinely restore alertness, but timing matters. Your brain enters progressively deeper stages of sleep the longer you’re out. After about an hour, you hit the deepest phase, called slow-wave sleep. Waking up during this stage causes sleep inertia, a period of intense grogginess and impaired function that can last 15 to 30 minutes and temporarily make you feel worse than before the nap.
To avoid this, keep naps under 30 minutes. That keeps you in lighter sleep stages, so you wake up refreshed rather than disoriented. If you have time for a full 90 minutes, that allows you to complete one entire sleep cycle and wake during a lighter phase again. The worst nap length is somewhere in between, around 45 to 60 minutes, where you’re deep enough to feel terrible when the alarm goes off.