How Much Sleep Do You Need? How To Calculate The Ideal Amount

With just 24 hours in the day, how many of them do you usually spend asleep? Do you feel that you sometimes just don’t quite get enough sleep?

The reality is that the amount of sleep you need depends on several different personal factors. That said, there’s plenty of medical guidance available about the optimal amount of sleep you should aim for.

And whilst many people try to survive on less sleep than the experts recommend, you may be affecting your long term well-being and health if you skimp on your sleep.

Equally, we’re all different. So whilst noting the broad expert advice, it’s good to work out just how much sleep you personally need to be at your best.

In this article you’ll find out about the latest recommendations for optimum sleep duration, based on different age groups. But I’ll also cover a practical way for you to try and work out the precise amount you personally need.

image showing how much sleep experts reccommend you have

How much sleep you need according to your age

There are many factors that can affect how much sleep you need from one day to the next, including:

  • Your age.
  • Your health.
  • How physically and mentally active you are.
  • Your diet and other lifestyle choices.
  • Your genetics.

In 2015, the US National Sleep Foundation produced new and detailed guidance on the ideal sleep duration for different age groups.

The foundation brought together a team of 18 sleep experts who analyzed over 2000 research studies. They eventually reduced this to just over 300 studies, which they then used to generate their final advice.

The team had leading experts from most relevant medical and research areas, including: sleep, physiology, anatomy, gerontology, pediatrics, gynecology and neurology.

It was an impressive team of experts conducting detailed research, so I suspect this will be the best advice for many years to come.

In addition to the ideal sleep duration, they also included two other recommendations:

  • May be appropriate: These sleep durations are probably okay and whilst they may not be the ideal, they shouldn’t cause undue concern.
  • Not recommended: These sleep durations are outside recommended limits. The advice follows that if you sleep for these times, you might want to consider talking to your doctor.

You can see their conclusions in the table below, which gives you a starting point to work out more accurately how much is right for you.

As an example: for adults under 65 they suggest the ideal duration is between 7 and 9 hours; equally 6 hours or 10 hours per night are probably okay too; but getting less than 6 or more than 10 hours sleep isn’t recommended.

sleep length
(total hours)
May be appropriate

(total hours)
Not recommended

(total hours)
0-3 Months
14 to 1711 to 13
18 to 19
Less than 11
More than 19
4-11 Months
12 to 1510 to 11
16 to 18
Less than 10
More than 18
1-2 Years
11 to 149 to 10
15 to 16
Less than 9
More than 16
3-5 Years
10 to 138 to 9
Less than 8
More than 14
6-13 Years
9 to 117 to 8
Less than 7
More than 12
14-17 Years
8 to 107
Less than 7
More than 11
Young adults
16-25 Years
7 to 96
10 to 11
Less than 6
More than 11
26-64 Years
7 to 96
Less than 6
More than 10
Older adults
Over 65
7 to 85 to 6
Less than 5
More than 9

Some people need much less sleep

You can see from the table that adults should be aiming for between 7 and 9 hours, and less than 6 hours isn’t recommended. So why is it then that some lucky people are fine with 6 hours sleep a night, or even less?

Part of the answer is that the amount of sleep you need might depend on your genetics. Unfortunately though, the gene which allows this miraculous sleep habit is only present in around 3% of people.

So the chances are you’re in the 97% that need an average of at least 7 hours per night. For most people though, getting much less than the ideal amount of sleep can result in long term health problems.

What about too much sleep?

Most people worry about not getting enough sleep. However, researchers have also found that too much sleep can also be bad for your health.

Too much sleep can be associated with a higher risk of being overweight, having a stroke, and developing diabetes or heart problems. You can find out more about these risks in the article about why people sleep.

How to work out exactly how much sleep you need

The medical guidance based on age isn’t very specific, for example saying adults need between 7 and 9 hours. So it may be useful to try and work out how much sleep you personally need.

Firstly, you might want to think about which of two questions you’d like to answer:

  • How much sleep do you need to get by?
  • How much sleep do you need to function optimally and be happiest?

The answer to these two questions could be quite different. For example, you may think that you can scrape through the day if you’ve had 6 hours sleep.

But is 6 hours enough to enjoy your day, and to function to a high standard all day long? Or does 6 hours turn you into a coffee fiend or make you look forward to going back to bed from the minute you wake up?

Keep a sleep diary

An excellent way to work out your optimum sleep time is to keep a sleep diary. In it you should record 4 things each day:

  • The time you went to sleep.
  • The time you woke up.
  • How long you slept for.
  • How you felt the next day.

For the time you went to sleep, try to work out when you fell asleep, not when you went to bed. It might be difficult if you’re tossing and turning for a while, but try to be as accurate as you can.

After a couple of weeks have a look back through your diary and do some analysis. If you felt alert, energized and able to do things well all day long, you probably got the right amount of sleep for those days.

But if you start feeling symptoms of sleep deprivation, you may not be getting enough sleep the night or two before.

You can continue doing this for as long as you like, and hopefully over the weeks or months you’ll find out exactly how much sleep works best for you.

If you want more accurate information over a period of time, or find keeping a diary a bit of a pain, then you could also think about investing in a sleep tracker.

You can find out about how they work and what options you have in our sleep tracker review.

image of a sleep diary

Sleep deprivation symptoms to watch out for

It’s possible to experience sleep deprivation without even being aware of it. Have a look at the following checklist and see if any apply to you when you come to fill in your sleep diary:

  • image of a woman sleeping and another woman who is tired at workAlways needing an alarm clock to wake up or using the snooze button a lot.
  • Finding it difficult to get out of bed in the morning.
  • Feeling sleepy in meetings, lectures, classes or warm environments.
  • Feeling very tired after a heavy meal, in the afternoons or even when driving.
  • Being grumpy or irritable.
  • Having difficulty concentrating, remembering things or finding it hard to make decisions.
  • Noticing a change in appetite or experience weight gain.
  • More accident prone.
  • It only takes you a couple of minutes to fall asleep at night.
  • Susceptible to colds and infections.
  • Stressful things are difficult to cope with.
  • Finding it hard to motivate yourself to do things.
  • Your reaction times are reduced.

There may of course be other explanations as to why you experience some of these. But in the context of experimenting to see how many hours sleep you need, you might find it helpful to note them down.

The trick is then to look back over your diary to see if you experience several of these on days when you’ve had less sleep, but not when you’ve had more sleep. That will then be a good indicator that you’re not getting enough sleep on those days.

After a couple of weeks you might find you can work out how many hours results in you writing something like ‘felt fine all day’ in the diary.

And wouldn’t it be great if you could not only decide how much sleep is best for you, but actually work towards achieving that amount on a regular basis – the holy grail!

Don’t panic if you’re not sleeping enough

It’s important to understand that even though these guidelines exist, you shouldn’t panic if you don’t always get that optimum amount.

For example, if you’ve worked out that your golden number of hours sleep is exactly 8, then the temptation will be to start worrying when you only get 7.

The reality though is that most people generally do manage to get by just fine on less sleep from time to time. If you have one of those nights when you just can’t seem to get to sleep easily, try not to worry that the next day will be awful. This will probably only keep you awake longer.

How much do you sleep?

How much sleep do you think you get on average, and how much do you think you need to be at your best? Feel free to leave a comment below.

4 CommentsLeave a comment

  • I need at least 8 hours of sleep to be fully rested and ready for work/school. However, sometimes when the time gets very busy that includes school + work, I would get only about 5 hours of sleep but then I would feel tired the whole day. On the weekends I love to sleep in for about 10 hours.

    • Hi Weston
      Thanks for your comment. I’m the same – about 8 hours is what makes me at my best I think. I know it’s tough when you sleep for much less than you’d like to; the next day can be difficult to get through. Maybe if you try sleeping for just the normal 8 hours at the weekend too, it might help stabilize your sleep pattern so you get 8 hours more regularly and not the 5 hours.


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