Sleep calculator: when to go to bed or wake up

Most adults need 7 to 9 hours

The NHS and the National Sleep Foundation (NSF) say 7 to 9 hours for adults, and the American Academy of Sleep Medicine (AASM) says at least 7. Teenagers need 8 to 10 hours, and children aged 6 to 12, 9 to 12.

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Bedtime is your wake-up time minus your sleep

The calculator works back from when you need to wake up and adds 15 minutes to fall asleep, close to the 16 minutes healthy sleepers took in a sleep laboratory. The NSF counts 30 minutes or less as a sign of good sleep.

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Sleep cycles aren't exactly 90 minutes

They run about 80 to 100 minutes, 4 to 6 a night, and vary from person to person and night to night.

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No trial shows waking at the end of a cycle helps

Studies of grogginess on waking disagree about whether the stage of sleep you wake from matters, and grogginess is worse after too little sleep. So the calculator plans by the hours for your age, and shows cycles only as an option.

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Short sleep catches up with you

Regularly sleeping less than 7 hours is linked with weight gain, diabetes, heart disease, depression and accidents, and people kept to 6 hours a night for two weeks performed as badly as after up to two nights without sleep.

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When a calculator isn't the answer

If you've had trouble sleeping for months, or you snore and stop breathing in your sleep, see a GP. If you work shifts, the hours for your age still matter, but fixed clock times won't fit your rota.

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The hours for your age

The calculator plans for the range each age group is given, from the body whose age bands fit best (our choice). Under 6, sleep totals include naps, so it shows the table instead of times.

• 6 to 12 years: 9 to 12 hours (AASM)
• 13 to 17 years: 8 to 10 hours (AASM and NSF)
• 18 to 64 years: 7 to 9 hours (NSF and NHS)
• 65 and over: 7 to 8 hours (NSF and the US Centers for Disease Control and Prevention, CDC), with a note that the US National Institute on Aging (NIA) says 7 to 9

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The sums

The headline uses the middle of your age's range: 8 hours for adults, 9 for teenagers, 10.5 for 6 to 12-year-olds and 7.5 from 65. The result also shows the earliest and latest times for the whole range (our choice). Times are to the minute and run on past midnight.

• Waking at a set time: bedtime = wake-up time - hours of sleep - time to fall asleep
• Going to bed at a set time: wake-up time = bedtime + time to fall asleep + hours of sleep

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Time to fall asleep

15 minutes by default, which you can change from 0 to 60 minutes in steps of 5. In 100 healthy sleepers in a sleep laboratory, falling asleep took a median of 16 minutes, from 3 to 119, and across many studies it lengthens by about a minute for each decade of age. Above 30 minutes, the result suggests seeing a GP if it happens most nights and has gone on for months.

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The evening before

From 13, the result works back from your bedtime with the NHS's advice: no tea or coffee in the 6 hours before bed, and relax for at least an hour before it. For 6 to 12-year-olds it suggests starting a wind-down routine 30 minutes before bed, as the NHS suggests for young children and the AASM's own bedtime calculator advises, with no caffeine line.

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Sleep cycles, as an option

Switch them on and the result lists bedtimes, or wake-up times, for 4, 5 or 6 blocks of 90 minutes, but only those inside the hours for your age: for adults, 5 blocks (7.5 hours) and 6 blocks (9 hours). They're labelled approximate, because real cycles run about 80 to 100 minutes, and no trial shows that waking at the end of one helps.

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Ticks that turn the times off

If you work shifts, the result gives no clock times: the hours for your age still apply, but fixed bedtimes don't fit a rota. If you have a sleep disorder or are having CBT for insomnia, it gives none either: follow the sleep window your clinician or programme sets.

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Bedtimes for common wake-up times (our arithmetic)

For an adult aged 18 to 64 needing 7 to 9 hours, with 15 minutes to fall asleep; the bedtime for 8 hours is in brackets.

• Waking at 5:00am: bed between 7:45pm and 9:45pm (8:45pm)
• Waking at 6:00am: 8:45pm to 10:45pm (9:45pm)
• Waking at 6:30am: 9:15pm to 11:15pm (10:15pm)
• Waking at 7:00am: 9:45pm to 11:45pm (10:45pm)
• Waking at 7:30am: 10:15pm to 12:15am (11:15pm)
• Waking at 8:00am: 10:45pm to 12:45am (11:45pm)

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Worked examples (our arithmetic)

As the calculator works them out.

• Age 35, waking at 7:00am, the calculator's starting values: get into bed at 10:45pm for 8 hours, or between 9:45pm and 11:45pm for 7 to 9. Last tea or coffee by 4:45pm, and start winding down at 9:45pm. With cycles on: 5 blocks, 11:15pm; 6 blocks, 9:45pm.
• Age 15, waking at 7:00am: 9:45pm for 9 hours, or 8:45pm to 10:45pm for 8 to 10. Only 6 blocks (9 hours) fits the teenage range: 9:45pm.
• Age 70, waking at 6:30am and taking 20 minutes to fall asleep: 10:40pm for 7.5 hours, or 10:10pm to 11:10pm for 7 to 8. Last tea or coffee by 4:40pm; start winding down at 9:40pm.
• Age 30, going to bed at 11:30pm: set the alarm for 7:45am, or between 6:45am and 8:45am.
• Age 8, waking at 7:00am: bed at 8:15pm for 10.5 hours, or between 6:45pm and 9:45pm for 9 to 12, with a wind-down routine from 7:45pm.
• Age 22, going to bed at 1:15am and taking 30 minutes to fall asleep: wake at 9:45am, or between 8:45am and 10:45am.

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How much sleep, by ageStrong evidence

The NSF's 2015 expert panel recommends 9 to 11 hours for school-age children, 8 to 10 for teenagers, 7 to 9 for adults and 7 to 8 for older adults, adding that "an additional hour or two on either side of a given range may be appropriate, depending on the person". The AASM: "Adults should sleep 7 or more hours per night on a regular basis", with 9 to 12 hours at 6 to 12 years and 8 to 10 at 13 to 18; the CDC gives 7 to 8 from 65. The NHS says "adults need 7 to 9 hours" on average, "although the exact amount can be different for each person", and the NIA says older adults need "about the same amount of sleep as all adults", 7 to 9 hours.

Sources 1, 2, 3, 4, 14, 15, 21, 22

Falling asleepEmerging evidence

In 100 healthy sleepers, falling asleep took a median of 16.1 minutes, ranging from 2.9 to 119; one in ten took more than 46 minutes (women) or 58 (men). The NSF's quality markers count falling asleep within 30 minutes, and being asleep for "7 out of 8 hours" in bed, as good. Across 169 studies, it took about 1.1 minutes longer for each decade of age.

Sources 5, 6, 16, 23, 24

Sleep cyclesStrong evidence

The US National Heart, Lung, and Blood Institute (NHLBI): "The cycle starts over every 80 to 100 minutes. Usually there are four to six cycles per night. You may wake up briefly between cycles." In 6,064 cycles recorded in 369 healthy people, the median was 96 minutes, with "a large interindividual variability", and the first cycle of the night was shorter. In 2,312 sleep recordings, cycles are "usually considered" to last about 90 minutes, 4 or 5 a night.

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Waking at the end of a cycleMixed evidence

A 2019 review of sleep inertia, the grogginess after waking, found "Mixed observations" on whether the stage of sleep you wake from matters: some studies found waking from deep sleep worse, others found no link. Grogginess is worse after sleep loss and at night. A "smart" bedroom alarm system had "little overall impact" in a small trial, and no trial we found tests planning sleep in 90-minute blocks.

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Too little sleepStrong evidence

"Sleeping less than 7 hours per night on a regular basis is associated with adverse health outcomes, including weight gain and obesity, diabetes, hypertension, heart disease and stroke, depression, and increased risk of death" (the AASM and Sleep Research Society). In a laboratory trial of 48 adults, 14 days of 6 hours or less a night caused deficits "equivalent to up to 2 nights of total sleep deprivation", while people felt only slightly sleepier.

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Catching up, and sleeping longEmerging evidence

In a laboratory trial of 36 adults, weekend lie-ins didn't prevent the effects of short weekday sleep on blood sugar control. In 16 cohort studies of 1,382,999 people, short sleep went with 12% and long sleep with 30% higher mortality, but long sleep may reflect illness: the AASM says regularly sleeping more than 9 hours "may be appropriate for young adults, individuals recovering from sleep debt, and individuals with illnesses".

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Treating insomniaStrong evidence

European and US guidelines put cognitive behavioural therapy for insomnia (CBT-I) first: the European guideline for "chronic insomnia in adults of any age", in person or digitally, and the AASM as a strong recommendation, advising against sleep hygiene tips on their own. In 20 trials, CBT-I helped people fall asleep 19 minutes faster and spend 26 fewer minutes awake in the night. The National Institute for Health and Care Excellence (NICE) recommends the digital programme Sleepio in primary care for people who would otherwise be offered sleep hygiene advice or sleeping pills.

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Teenagers' body clocksStrong evidence

Around puberty most teenagers' sleep shifts later, by "up to 2 hours", and the American Academy of Pediatrics (AAP) says the average teenager "has difficulty falling asleep before 11:00 pm and is best suited to wake at 8:00 am or later". It puts the best amount for most teenagers at 8.5 to 9.5 hours.

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Older adultsStrong evidence

Older adults "tend to go to bed earlier and wake up earlier", and sleep "tends to be shorter and lighter", with more waking in the night (NIA). Across many studies, the share of time in bed spent asleep fell by about 2% a decade.

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Shift workStrong evidence

Night workers' day sleep "is often lighter, shorter and more easily disturbed", and "there is no single optimal shift system that suits everyone" (the Health and Safety Executive, HSE). The NHS lists shift work among the most common causes of insomnia.

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What a cycle is

Through the night, sleep moves between non-REM sleep, which includes deep sleep, and rapid eye movement (REM) sleep, with more deep sleep early in the night and more REM later. One round is a cycle.

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Why 90 minutes drifts

Five cycles of 80, 90, 96 or 100 minutes end at 6 hours 40 minutes, 7 hours 30 minutes, 8 hours or 8 hours 20 minutes, so a plan built on 90 minutes can be 50 minutes out by morning, even inside the normal range (our arithmetic).

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What the calculator does

It plans by the hours for your age. Switch on cycles and you'll see the 90-minute blocks that fit inside those hours, labelled approximate.

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What matters more

Enough sleep, at regular times: the NHS says "wake up and get out of bed at the same time every day", and the AASM's guideline for insomnia includes waking at the same time every morning. Grogginess is worse after too little sleep.

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Insomnia

"Insomnia means you regularly have problems sleeping". If it lasts 3 months or longer it's called long-term insomnia; the NIA's definition adds "at least three nights a week". See a GP if changing your sleeping habits hasn't helped, you've had trouble sleeping for months, or it's affecting your daily life in a way that makes it hard for you to cope.

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Treatment

A GP may offer CBT, face to face or through an online programme, and NICE recommends Sleepio. "GPs now rarely prescribe sleeping pills", and pharmacy sleep aids "cannot cure insomnia but may help you sleep better for 1 to 2 weeks".

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Sleep apnoea

See a GP if your breathing stops and starts while you sleep, you make gasping, snorting or choking noises, or you always feel very tired during the day. It can be hard to tell yourself: the NHS says "it may help to ask someone to stay with you while you sleep so they can check for the symptoms".

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Driving

Don't drive when you feel sleepy. The Highway Code says driving when you're tired "greatly increases your risk of collision", and advises avoiding long journeys between midnight and 6am and taking a break of at least 15 minutes every 2 hours. You must tell the Driver and Vehicle Licensing Agency (DVLA) if you have moderate or severe obstructive sleep apnoea with excessive sleepiness, narcolepsy or cataplexy, or another sleep condition that has made you excessively sleepy for at least 3 months.

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Medicines

Many medicines can cause insomnia. If you think yours might, speak to a GP or pharmacist.

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Shift workers

Tick the box and the calculator gives no clock times. The hours for your age still apply over 24 hours, but no single shift pattern suits everyone, and the HSE says "The legal duty is on employers to manage risks from fatigue". See a GP if sleep problems last.

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Long-term insomnia, or CBT for insomnia

CBT-I's sleep restriction sets your time in bed to match the time you actually sleep, and a bedtime calculator would undo that: follow the window your therapist or programme gives you. Sleep restriction can make you sleepy in the day, and the AASM's guideline notes it may not suit people in high-risk jobs, such as drivers.

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A sleep disorder

If you might have sleep apnoea, restless legs or another sleep disorder, the right bedtime won't fix it. See a GP; our sleep apnoea guide explains the signs.

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Under 6

Sleep totals include naps, and babies vary so much that the AASM gives no figure under 4 months. The calculator shows the table instead. The NHS suggests a calm bedtime routine at the same time each night, and your health visitor can help.

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Teenagers

The calculator works for 13 to 17-year-olds, with a note: their body clocks shift later, so an early school start can make 8 to 10 hours hard. That's biology, not laziness. A regular wake-up time still helps.

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Worry or low mood keeping you awake

Stress, anxiety and depression are among the most common causes of insomnia. The support section below has where to get help, and our anxiety and depression guides cover what exercise can do.

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"Everyone needs 8 hours"Strong evidence

Guidelines give ranges: 7 to 9 hours for most adults, or 7 or more, and the NHS says "the exact amount can be different for each person".

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"A sleep cycle is exactly 90 minutes"Strong evidence

Cycles run about 80 to 100 minutes; measured cycles had a median of 96 minutes with wide variation, and the first is shorter.

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"Wake at the end of a cycle and you'll feel refreshed"Mixed evidence

The evidence on sleep stage and grogginess is mixed, no trial shows that planning in 90-minute blocks helps, and grogginess is worse after too little sleep.

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"Older people need less sleep"Strong evidence

The NIA says about 7 to 9 hours, the same as other adults, and the NSF 7 to 8 from 65. Sleep gets lighter and earlier with age, but the need doesn't shrink much.

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"You can train yourself to need less sleep"Strong evidence

After 14 days of 6 hours a night, people performed as if they'd gone up to 2 nights without sleep, while feeling only slightly sleepier.

Source 11

"I'll catch up at the weekend"Emerging evidence

In a laboratory trial, weekend lie-ins didn't prevent the effects of short weekday sleep on blood sugar control, and the NHS advises keeping the same wake-up time and not sleeping in after a bad night.

Sources 1, 26

"If you can't sleep, stay in bed and keep trying"Strong evidence

CBT-I's stimulus control says to go to bed only when sleepy and to get out of bed when you can't sleep, and the NHS says "only go to bed when you're sleepy".

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"The more sleep the better"Mixed evidence

More than 9 hours may suit young adults, people recovering from lost sleep and people who are ill, but for others its effect on health is uncertain, and long sleep went with higher mortality in cohort studies, where illness may explain it.

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"Teenagers sleep late because they're lazy"Strong evidence

Puberty shifts the body clock up to 2 hours later, and the average teenager finds it hard to fall asleep before 11pm.

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Trouble sleeping

See a GP if changing your habits hasn't helped, you've had trouble sleeping for months, or it's hard to cope. NHS Every Mind Matters has free advice on sleep, including a 6-week email programme.

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Worry, stress or low mood

Stress, anxiety and worry can keep you awake. You can refer yourself to NHS talking therapies for anxiety and depression without seeing a GP, if you're 18 or over (16 in some areas) and registered with a GP.

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Urgent help

If you need urgent help for your mental health, call 111 and choose the mental health option, or ask for an urgent GP appointment. You can talk to Samaritans on 116 123, or Childline on 0800 1111 if you're under 19. Call 999 or go to A&E if someone's life is at risk, or you don't feel you can keep yourself or someone else safe.

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Snoring and stopping breathing

See a GP if your breathing stops and starts in your sleep, you make gasping, snorting or choking noises, or you always feel very tired during the day.

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Shift work

If your shifts leave you exhausted, talk to your employer or occupational health team (our suggestion): the HSE says the legal duty to manage risks from fatigue is on employers, and night workers' day sleep is often lighter and shorter.

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