How much sleep do you need, and is 6 hours enough?

How much sleep do you need?

It's gone midnight and you're counting forward to the alarm. Six hours, if you drop off now. Is 6 hours of sleep enough to get through tomorrow, or are you already running short?

Most adults need 7 to 9 hours a night, the NHS says, though the exact amount differs from person to person [1]. Two US sleep societies agree on the lower end. Their experts advise adults aged 18 to 60 to sleep 7 hours or more a night, regularly [2].

The US National Sleep Foundation sets out a range for every age. Its expert panel also named a wider band that may suit some people, because a few people do well on a little less or need a little more [3].

The hours are for sleep, not time in bed. Everyone needs a different amount, so treat the table as a guide rather than a target to hit to the minute [1].

Is 6 hours of sleep enough?

For most adults, no. Six hours falls below the recommended 7 to 9, though the National Sleep Foundation's panel rated it as possibly fine for some people [3].

The bigger problem is that short sleep is hard to judge from the inside. In a US lab study, 48 healthy adults aged 21 to 38 spent two weeks with 4, 6 or 8 hours in bed a night, while another group went 3 nights without sleep. By the end, the 6-hour group did as badly on attention and memory tests as people who'd missed a whole night's sleep. Yet they rated themselves only slightly sleepy Moderate [4].

So feeling fine on 6 hours isn't proof that you are. The 8-hour group, by contrast, showed only small changes that weren't significant over the two weeks [4].

Is 7 hours of sleep enough?

For most adults, yes. Seven hours is the lower end of both the NHS range and the US guidance, and the US sleep societies set it as the minimum for adults [1][2].

If you're getting 7 hours and waking up refreshed, with enough energy for the day, that's a good sign. If you're still tired, you may need closer to 8 or 9.

Is 5 or 4 hours of sleep enough?

No, not for most people. For adults under 65, the National Sleep Foundation doesn't recommend less than 6 hours. For people aged 65 and over, 5 to 6 hours may suit some, but 7 to 8 is still the recommended range [3].

In the same two-week lab study, people with 4 hours in bed a night did as badly on attention and memory tests as people who'd gone two nights without any sleep [4].

A few people really do need less. Some families carry rare gene changes that let them feel rested on 4 to 6.5 hours a night. One such change was found in about 4 in 100,000 people Early [5]. So if you sleep 5 hours and feel tired, it's far more likely you're short of sleep than that you're a natural short sleeper.

Can you sleep too much?

Possibly, but it's hard to say. The US sleep societies say sleeping more than 9 hours regularly may be right for young adults, people catching up on lost sleep and people who are ill. For everyone else, they say, it's uncertain whether it carries a health risk [2].

Studies that follow large groups of people have found links at both ends. Across 16 studies of 1.4 million people, short sleepers, commonly under 7 hours a night, were 12% more likely to die during the studies. Long sleepers, commonly over 8 or 9 hours, were 30% more likely, compared with people sleeping 7 to 8 hours Moderate [6].

These studies can't show that sleep length was the cause. The authors suggest that long sleep may be a sign of illness rather than its cause, and that depression, poor health and low activity are all linked with sleeping longer [6]. If you've started sleeping much more than usual and don't know why, it's worth mentioning to your GP.

How much deep sleep do you need?

Sleep isn't one long stretch of the same thing. Through the night you move between light sleep, deep sleep and REM (rapid eye movement) sleep. There's no set amount of deep sleep anyone needs, but sleep-lab studies show what's typical.

In a US study of 35 healthy adults aged 20 to 50, a full overnight sleep test measured these amounts in a night of just over 7 hours Early [7].

Deep sleep tends to fall as you get older. In older sleep-lab studies, total sleep dropped by about 10 minutes and deep sleep's share of the night by about 2% with each decade of age [8]. That's a normal part of ageing, not a sign that something's wrong.

If you check a sleep tracker, take its stage numbers loosely. In the same US study, the Apple Watch's "Core" sleep matched light sleep, and the watch underestimated deep sleep by 43 minutes. The study was funded by Oura, whose ring came closest to the lab test [7].

Can you catch up on lost sleep?

Saturday morning, the alarm's off, and a long lie-in feels like paying the week back. It helps a little, but not hour for hour.

In a US lab study, healthy young adults were given 5 hours of sleep a night during the week, then a weekend of unlimited sleep. The weekend won back only about an hour of the 12 or more hours they'd lost Early [9].

The NHS advises against sleeping in after a bad night, and suggests sticking to your usual sleep times instead [1]. So a steady bedtime and wake time is the better plan. Our guide to healthy habits covers how to make a routine stick.

Signs you're not getting enough sleep

"You probably do not get enough sleep if you're constantly tired during the day," the NHS says [1].

The NHS also says not to drive when you feel sleepy [1]. If you're short of sleep, our guide on how to fall asleep fast has gentle steps you can start tonight, and our guide to magnesium for sleep covers what the research shows.

See a GP if changing your sleep habits hasn't helped, if you've had trouble sleeping for months, or if it's making daily life hard to cope with [1].

Frequently asked questions

Is 8 hours of sleep enough?

Yes, for most adults. Eight hours sits in the middle of the 7 to 9 hours the NHS gives for adults [1]. Some people need a little more, and that's normal too.

How much sleep do women need?

The same as men. The National Sleep Foundation's ranges are the same for women and men [3]. In sleep-lab studies, women slept slightly longer and had a little more deep sleep than men of the same age, but the differences were modest [8]. The NHS lists the menopause among the causes of poor sleep [1].

How much core sleep do you need?

There's no target. "Core" is the Apple Watch's name for light sleep, which made up just over half the night in a sleep-lab study [7]. Trackers estimate sleep stages, so their numbers are a rough guide.

Can you sleep 8 hours in 4 hours?

No. An expert panel for the US National Sleep Foundation found no evidence that splitting sleep into several short naps brings any benefit, and it advises against cutting sleep this way [10].

Can you die from lack of sleep?

Short sleep is linked with a slightly higher risk of dying early, though studies can't show it's the cause [6]. Short sleep is also linked with accidents [2], which is why the NHS says not to drive when you feel sleepy [1].

Do you need less sleep as you get older?

A little. The recommended range is 7 to 9 hours for adults up to 64 and 7 to 8 hours from 65 [3]. Sleep also tends to get lighter and shorter with age [8].

References

Every study here is listed so you can read it yourself. This guide is for general information and doesn't replace advice from your GP or pharmacist. We review it when new research is published.

1. NHS. Insomnia. Accessed 18 October 2026. nhs.uk/conditions/insomnia
2. Watson NF, Badr MS, Belenky G et al. (2015). Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep 38(6): 843–844. PMID 26039963
3. Hirshkowitz M, Whiton K, Albert SM et al. (2015). National Sleep Foundation's updated sleep duration recommendations: final report. Sleep Health 1(4): 233–243. PMID 29073398
4. Van Dongen HP, Maislin G, Mullington JM et al. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep 26(2): 117–126. PMID 12683469
5. Shi G, Xing L, Wu D et al. (2019). A rare mutation of β1-adrenergic receptor affects sleep/wake behaviors. Neuron 103(6): 1044–1055.e7. PMID 31473062
6. Cappuccio FP, D'Elia L, Strazzullo P et al. (2010). Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep 33(5): 585–592. PMID 20469800
7. Robbins R, Weaver MD, Sullivan JP et al. (2024). Accuracy of three commercial wearable devices for sleep tracking in healthy adults. Sensors 24(20): 6532. PMID 39460013
8. Ohayon MM, Carskadon MA, Guilleminault C et al. (2004). Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan. Sleep 27(7): 1255–1273. PMID 15586779
9. Depner CM, Melanson EL, Eckel RH et al. (2019). Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep. Current Biology 29(6): 957–967.e4. PMID 30827911
10. Weaver MD, Sletten TL, Foster RG et al. (2021). Adverse impact of polyphasic sleep patterns in humans: report of the National Sleep Foundation sleep timing and variability consensus panel. Sleep Health 7(3): 293–302. PMID 33795195