Most adults need 7 to 9 hours of sleep per night. That range comes from the National Sleep Foundation’s expert panel, which reviewed thousands of studies to set guidelines for every age group. The CDC draws a firmer line: adults aged 18 to 60 should get at least 7 hours. But the “right” number for you depends on your age, your body, and whether the sleep you’re getting is actually restful.
Recommended Hours by Age
Sleep needs change dramatically over a lifetime. Newborns (0 to 3 months) need 14 to 17 hours. Infants (4 to 11 months) need 12 to 15. Toddlers drop to 11 to 14 hours, and preschoolers (ages 3 to 5) need 10 to 13. School-age children between 6 and 13 should get 9 to 11 hours, and teenagers between 14 and 17 need 8 to 10.
For young adults (18 to 25) and adults (26 to 64), the recommended range is 7 to 9 hours. Adults 65 and older need slightly less, around 7 to 8 hours. These are ranges for a reason. Some people genuinely function well at the lower end, while others consistently need closer to 9 hours to feel sharp. The key is that very few healthy adults can thrive on less than 7.
Why 6 Hours Isn’t Enough
People who sleep 6 hours often say they feel fine, but performance testing tells a different story. Chronic sleep deprivation slows reaction times, impairs decision-making, and disrupts how your body processes blood sugar, raising the risk of Type 2 diabetes over time. The tricky part is that your brain adapts to feeling tired. After a few weeks of short sleep, you stop noticing how impaired you are, even though the impairment is measurable.
Sleep debt also builds faster than most people realize. Losing just one hour of sleep per night can take up to four days of adequate sleep to recover from. A full week of short nights can take up to nine days to reverse. So the idea of “catching up on the weekend” works only if your deficit is small.
Too Much Sleep Is a Problem Too
Regularly sleeping more than 9 hours as an adult is linked to its own set of health risks: Type 2 diabetes, heart disease, obesity, depression, and a greater overall risk of dying from a medical condition. Oversleeping itself may not always be the direct cause. It often signals something else going on, like an underlying condition (depression, thyroid dysfunction, heart disease) or consistently poor sleep quality that leaves your body trying to compensate with more time in bed.
If you’re sleeping 9 or more hours and still waking up exhausted, that pattern is worth paying attention to. The issue is probably not that you need more hours. It’s that the hours you’re getting aren’t doing their job.
Quality Matters as Much as Quantity
Not all sleep is equal. Your brain cycles through different stages each night, and one of the most important is deep sleep, the phase where your body repairs tissue, strengthens the immune system, and consolidates memory. Adults should spend about 20% of total sleep time in deep sleep. For an 8-hour night, that works out to roughly 60 to 100 minutes.
Several things can reduce deep sleep even when you’re in bed long enough: alcohol (which fragments sleep cycles), a warm bedroom, caffeine consumed within 6 to 8 hours of bedtime, inconsistent sleep and wake times, and screen exposure close to bedtime. You can sleep 8 hours and still wake up groggy if most of that time was spent in lighter stages.
A useful self-check: if you fall asleep within about 10 to 20 minutes of lying down, wake up without an alarm (or shortly before it), and don’t feel a strong pull to nap during the afternoon, your sleep quality is probably solid. If you’re dragging through the day despite what looks like enough time in bed, the structure of your sleep may be off.
How to Tell if You’re Getting Enough
The simplest test is how you feel between 1 and 3 p.m., when your circadian rhythm naturally dips. Mild drowsiness is normal. Struggling to keep your eyes open or needing caffeine to function is not. Clinicians use the Epworth Sleepiness Scale, a quick questionnaire that scores your likelihood of dozing off in everyday situations on a scale of 0 to 24. A score between 0 and 10 is considered normal daytime sleepiness. Anything from 11 to 15 suggests mild to moderate excessive sleepiness, and scores above 16 point to a severe problem.
You can also run a simple experiment on your next vacation or stretch of days without obligations. Go to bed when you’re tired, don’t set an alarm, and track how long you sleep after the first two or three nights (the early nights will be inflated by accumulated debt). The number you settle into by night four or five is a good approximation of your biological need.
Building a Consistent Sleep Schedule
Your body’s internal clock responds most to consistency. Going to bed and waking up at roughly the same time every day, including weekends, reinforces your natural circadian rhythm and makes it easier to fall asleep and wake up without effort. A 30-minute window on either side is realistic for most people.
If you’re currently averaging 6 hours and want to reach 7.5, don’t shift your bedtime by 90 minutes overnight. Move it earlier by 15 to 20 minutes every few days. Your body adjusts gradually, and forcing a dramatically earlier bedtime usually just means lying awake, which can create its own anxiety around sleep. Pair the earlier bedtime with a wind-down period of 30 to 60 minutes: dim lights, no screens or at least a blue-light filter, and a cool room (around 65 to 68°F for most people).
The bottom line is straightforward. Most adults land somewhere between 7 and 8.5 hours when given the chance to sleep freely. If you’re consistently below 7, you’re accumulating a debt that affects your body in ways you may not notice day to day but that compound over months and years.