Most adults need around seven to nine hours of sleep a night. That is the figure the NHS gives, and it matches the widely cited guidance from an expert panel convened by the US National Sleep Foundation, which reviewed the research in 2015 and settled on seven to nine hours for adults aged 18 to 64, and seven to eight for those aged 65 and over.
The range is not a hedge. Sleep need varies from person to person in much the same way height does, and it is set mostly by genes rather than willpower. Some people are genuinely fine on seven hours; others are not themselves on less than nine. The useful question is not "what is the right number?" but "what is my number, and am I getting it?"
Where the seven-to-nine figure comes from
Sleep researchers arrive at recommendations in two ways. They look at how people perform on tests of attention, memory and mood after different amounts of sleep, and they look at large population studies that follow people's sleep and health over years. Both point the same way. Below about seven hours, most adults show measurable dips in reaction time, concentration and emotional balance, and long-term studies link habitual short sleep to higher rates of heart disease, type 2 diabetes and depression.
Those studies show association rather than proof of cause, and there are plenty of individual exceptions. But the pattern is consistent enough that seven hours is a sensible lower bound for the majority.
The unsettling finding is that people adapt to the feeling of short sleep without adapting to its effects. In a well-known study by Van Dongen and colleagues, published in the journal Sleep in 2003, adults restricted to six hours a night for two weeks accumulated attention lapses comparable to a night or two without sleep at all, while rating themselves as only mildly sleepy. If you have "got used to" six hours, that may be what has happened.
Signs you are not getting enough
- You need an alarm to wake, every day, and you would sleep on without it.
- You fall asleep within a couple of minutes of your head touching the pillow. This sounds like good sleep; it is more often a sign of a large sleep debt.
- You feel a heavy dip in the mid-afternoon that coffee only partly lifts.
- You sleep an hour or two longer at weekends or on holiday.
- You doze in front of the television, in meetings or, most seriously, at the wheel.
- Your mood is thinner: more irritable, less patient, quicker to feel overwhelmed.
None of these on its own proves anything. Several together are a fairly reliable signal.
How to find your own number
The cleanest test is a week with no alarm, which most people cannot arrange. A fair substitute is to notice your sleep on the last few days of a holiday, once the initial catch-up has passed. The amount you sleep naturally then, waking without an alarm and feeling reasonably alert within half an hour, is close to your real need.
At home, work backwards. Fix the time you have to get up, count back the hours you think you need, add fifteen to twenty minutes for falling asleep, and try it for two weeks. If you are still tired, go to bed twenty minutes earlier. Keeping a simple record of bedtime, wake time and how you felt makes this much easier to judge, and a consistent sleep schedule makes the results easier to trust.
In short: Seven to nine hours for most adults, seven to eight after 65. If you need an alarm every day and sleep much longer at the weekend, you are probably under your own number.
Why quality and regularity matter as much as hours
Eight hours of broken sleep is not the same as eight hours of solid sleep. Sleep moves through cycles of lighter, deeper and dreaming sleep roughly every ninety minutes, and frequent wakings, alcohol, pain or a warm room can cut into the deeper stages while leaving the total hours looking fine.
Regularity matters more than most people expect. Going to bed and getting up at roughly the same times each day keeps your body clock aligned with your life, so the hours you do get fall at the time your body is best at using them. A late night and a lie-in at the weekend can leave you feeling jet-lagged on Monday even if you slept plenty. Our guide to whether you can catch up on sleep looks at what the weekend lie-in really does.
Naps count towards the total, but a long or late one takes sleep pressure away from the night. If you nap, keeping it short and early protects the night.
Older adults
Sleep changes with age. From the fifties onwards, deep sleep becomes shallower and shorter, people wake more often, and many find themselves sleepy earlier in the evening and awake earlier in the morning. Total need drops only a little, to around seven to eight hours, but getting it in one block becomes harder.
This is normal ageing rather than a problem to solve, though it does mean being more careful with the things that fragment sleep further: alcohol in the evening, caffeine after lunch, a bedroom that is too warm, and long naps in the afternoon. If you are over 65, sleeping poorly and it is affecting your days, do not put it down to age. It is still worth raising with a GP.
When to worry
Getting less than seven hours occasionally is life. Getting less than six most nights, or getting eight and still struggling through the day, is worth attention. Persistent daytime sleepiness despite enough time in bed can point to something that breaks up sleep without fully waking you, such as sleep apnoea, and that is a medical question rather than a habits one. Our guide on when to see a GP about sleep lists the signs that matter.
Where to go next
Pick a wake time you can keep seven days a week, count back your best guess at your number, and try it for a fortnight before adjusting. If falling asleep or staying asleep is the problem rather than the hours, start with why can't I sleep. For more short answers, browse the rest of our sleep questions.
Frequently asked questions
Is 6 hours of sleep enough?
For most adults, no. Six hours sits below the seven to nine hours recommended for adults, and research on restricted sleep suggests people adapt to feeling tired without adapting to the effects on attention and mood. A small minority genuinely do well on six; the test is how you function on a free day with no alarm.
Do you need less sleep as you get older?
Slightly. The widely cited guidance suggests seven to eight hours for adults over 65, compared with seven to nine for younger adults. Older adults also sleep more lightly and wake earlier, which can look like needing less sleep when it is really sleep being spread differently across the day.
Can you sleep too much?
Regularly sleeping more than nine or ten hours as an adult is worth a second look, not because sleep itself is harmful but because it can be a sign of poor-quality sleep, low mood or another health issue. If you are sleeping long and still tired, mention it to your GP.
Is 8 hours a rule?
No. Eight hours is the middle of a range, not a target. Plenty of well-rested people sleep seven and a quarter hours. Chasing a number often backfires, because lying in bed trying to reach it produces exactly the wakeful, frustrated time in bed that makes sleep worse.
Sources and further reading
- NHS: Sleep and tiredness
- Sleep Foundation: How much sleep do you need?
- CDC: About sleep
Written and reviewed by the Quiet Mind Sleep editorial team in line with our editorial policy. Spotted an error? Let us know.
