Sleep Calculator: What Time Should I Go to Bed, and How Much Sleep Do I Need?

Sleep calculator: bedtime by wake-up time

Times include about 15 minutes to fall asleep.

Sleep talking is another common, usually harmless night-time habit. If it bothers you or a partner, see how to stop sleep talking.

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Only 4 cycles (6 hours)? That’s less than most adults need. Try to make it the exception, not the rule. Our guide to the best time to go to bed adds an 8-hour column and a 5am row.

How many hours of sleep do I need? (by age)

Most adults need 7 to 9 hours of sleep a night, the NHS says. Older adults tend to need slightly less (about 7 to 8 hours), teenagers more (8 to 10) and children more again. The NHS gives these averages, and an expert panel convened by the US National Sleep Foundation reached similar ranges in 2015 after reviewing the research:

These are averages, and the NHS points out that everyone needs a different amount. The panel also noted that sleeping well outside the normal range is rare, and that people who habitually do so may be showing signs of a health problem. For worries about a child’s sleep, talk to your GP or health visitor. Our products are for adults only.

How do I know how much sleep I need?

The simplest test is how you feel. If you wake reasonably refreshed and stay alert through the day without leaning on caffeine, you’re probably getting enough. The NHS says you probably aren’t getting enough if you’re constantly tired during the day.

To find your own number, use a free week or a holiday. Go to bed when you feel sleepy and wake without an alarm. The first few nights are usually longer as you catch up, then your sleep settles close to your natural need. A Japanese lab study found that ideal sleep length varies between individuals, and that just 1 hour of hidden sleep debt took about four days to recover. Our sleep debt guide shows how to work out yours. If you regularly need 10 hours or more and still feel unrefreshed, read about oversleeping and speak to your GP.

Planning a wind-down to match your bedtime? Our guide to the best magnesium drinks in the UK compares evening options, from cans to berry powders.

Is 7 hours of sleep enough?

For many adults, yes. Seven hours sits at the bottom of both the NHS range and the National Sleep Foundation panel’s range for adults, so it counts as enough sleep rather than a shortfall. If you get 7 hours and feel fine all day, there’s no need to chase more.

Two things matter more than the number itself:

• Is it 7 hours asleep, or 7 hours in bed? Most people take 10 to 20 minutes to drop off and wake briefly in the night, so 7 hours in bed is often closer to 6.5 hours of sleep. Allow about 7.5 hours in bed (5 cycles) if you want a true 7.
• How do you feel? If you get 7 and still feel tired, need an alarm to drag you up or sleep much longer at weekends, you may be one of the people who need 8 or 9 hours, or your sleep may be broken. See why you wake up tired.

For people over 65, 7 hours sits in the middle of the panel’s 7 to 8 hour range, so it is usually plenty. Our guide to sleep as you get older explains why sleep gets lighter with age.

Is 6 hours of sleep enough?

For most adults, no. Six hours is below the 7 to 9 hours the NHS recommends, and the evidence suggests it costs more than people notice.

In a well-known lab study, healthy adults allowed 6 hours in bed for 14 nights built up thinking and reaction-time problems equivalent to up to two nights with no sleep at all. Their sleepiness ratings barely rose after the first few days, so they largely didn’t realise how impaired they were. That is the trap with 6 hours: it can feel normal while performance slides. Read more about the effects in sleep deprivation.

A few people really do thrive on less. Scientists have found a gene mutation (in a gene called DEC2) in people who naturally sleep much less than average. But the National Sleep Foundation panel notes that sleeping far outside the normal range is rare. If you need an alarm, sleep in on days off or flag in the afternoon, 6 hours is far more likely to be leaving you short.

Is 6 hours enough for a teenager?

No. Teenagers need around 8 to 10 hours, so 6 hours leaves them 2 to 4 hours short every night.

If you can’t get more than 6 hours however early you go to bed, that may be insomnia rather than a choice, and it’s worth talking to your GP.

How sleep cycles work

Each night you move through about 4 to 6 cycles, averaging roughly 90 minutes each. That’s an average rather than a fixed number: Cleveland Clinic puts a typical cycle at about 90 to 120 minutes, and lab research shows cycle length differs from person to person. Each cycle has stages:

Waking during deep sleep is more likely to leave you groggy. Waking at the end of a cycle, during lighter sleep, often feels easier.

Morning light helps set your body clock. On dark winter mornings some people use a light box: our guide answers do SAD lamps work and how to use one.

How many sleep cycles do I need?

Most adults do best with 5 to 6 cycles a night, which lines up with 7.5 to 9 hours. There is no official target for cycles: the advice is about total sleep, and 5 to 6 cycles is simply how the NHS’s 7 to 9 hours divides into 90-minute blocks.

Deep sleep is front-loaded into the first cycles, and the longest REM periods come in the last ones. So cutting your night short eats into REM in particular. A wearable can estimate your cycles, though not precisely: see do sleep trackers work?

Most dreaming happens in REM sleep, which makes up more of each cycle towards morning. If your dreams feel unusually intense, see our guide to vivid dreams.

Wake-up time by bedtime

Napping? A 10 to 20 minute nap avoids deep sleep, or a full 90-minute cycle avoids grogginess. See power naps.

Best time to sleep and wake up

There’s no single best clock time for everyone. What matters most is getting enough sleep and keeping your sleep and wake times steady. For most people waking between 6am and 7.30am, the charts above put bedtime in the 10pm to 11pm window.

Your circadian rhythm shifts that window a little either way. If you’re naturally a night owl, move your alarm 15 to 30 minutes earlier every few days rather than jumping straight to an early bedtime. Our full guide to the best time to sleep covers chronotypes, teenagers and shift work, and these tips to wake up early help the new time stick.

Does timing your cycles really work?

It’s a useful rule of thumb, but not exact. Cycle length varies between people and through the night, and it takes different amounts of time to fall asleep. What matters most is getting enough sleep and keeping the same wake time every day, including weekends. Your body clock then settles, and you’ll start waking more naturally.

If you keep waking groggy, nudge your bedtime 15 minutes earlier or later for a week and see which feels better.

Tips to hit your bedtime

• Set a “wind-down” alarm an hour before bed. See our bedtime routine for adults.
• Dim the lights and put screens away. See revenge bedtime procrastination.
• Keep caffeine to before midday.
• Have a warm, caffeine-free drink. See best tea for sleep.
• Can’t drop off? See how to fall asleep fast.

Magnesium contributes to a reduction of tiredness and fatigue and to normal psychological function. Our Magnesium Glycinate Sleep Complex is a berry bedtime drink, and our Sleep CBD Oil pairs broad spectrum CBD with passion flower for evenings.

The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.

Related guides

• Struggle to go to bed earlier? See night owl: how to wake up earlier.
• Still groggy in the morning? See why do I wake up tired?
• For what happens when you don’t get enough, see sleep deprivation.
• 10 tips to wake up early and feel awake.
• Curious how a ring or watch estimates your sleep stages? See do sleep trackers work?
• Circadian rhythm vs sleep cycle: what is the difference?.
• Wondering how much sleep is too much? See oversleeping.
• Deep sleep explained: how much you need and how to get more.
• How to work out your sleep debt.
• For what the research says about bedtimes, read our guide to the best time to sleep.
• How much REM sleep you need by age.
• Need to move your bedtime? Our guide to fixing your sleep schedule has a 7-day plan.
• How to shift your bedtime before a long flight.
• Lucid dreaming techniques that use sleep cycles.
• If you get enough hours but still wake exhausted, see sleep apnoea: signs, tests and what helps.
• If the clocks are about to change, read whether you really get an extra hour of sleep before you set your new bedtime.
• If you use magnesium as part of your wind-down, our guide to the best magnesium for sleep covers which type and when to take it.
• Most people over 65 still need 7 to 8 hours: see how much sleep older people need.