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Is 8 Hours of Sleep Enough? First, Find Out Your Sleep Need

Person waking up and yawning, looking at alarm clock wondering if 8 hours of sleep is enough

“Get 8 hours of sleep” is said so often it’s almost a cliché. It’s the most commonly recommended amount, so it’s no wonder many people think eight is the magic number to aim for. And according to the National Sleep Foundation, healthy adults should aim for seven to nine hours, so eight hours feels like the perfect middle ground. But is eight hours of sleep really enough?

Below, we dive into whether eight hours is enough sleep, why you might be tired even though you get this amount, and times when you’ll need more sleep than this. 

Is 8 Hours Enough Sleep?

When we talk about getting enough sleep, there isn’t a one-answer-fits-all response. Guidelines from bodies such as the National Sleep Foundation are exactly that: guidelines. They don’t take into account individual sleep needs. 

Our sleep need is determined by genetics, just like height and eye color. One study suggests the average sleep need is 8 hours 40 minutes, plus or minus 10 minutes or so, but 13.5% of us may need 9 hours or more sleep a night.

One paper looking into the ideal amount of sleep concluded: “Sleep duration recommendations issued by public health authorities are important for surveillance and help to inform the population of interventions, policies, and healthy sleep behaviors. However, the ideal amount of sleep required each night can vary between different individuals due to genetic factors and other reasons, and it is important to adapt our recommendations on a case-by-case basis.” 

It added recommendations are largely reliant on observational studies and self-reported sleep duration. And it’s difficult to accurately measure how much sleep you get each night by yourself, so these guidelines may be based on incorrect data. Plus, they’re looking at how much sleep people are getting, not how much they actually need.  

The researchers of the paper also said: “There is no magic number or ideal amount of sleep to get each night that could apply broadly to all. The optimal amount of sleep should be individualized, as it depends on many factors.”

So, while some of us may indeed have a sleep need of exactly eight hours, many of us may need more than this, meaning just getting eight hours of sleep a night isn’t enough to feel and perform at our best. 

One way to find out your sleep need is to use the RISE app. RISE uses your phone use behavior and proprietary sleep-science-based models to work out your sleep need. This way, you don’t need to rely on generic guidelines, and you can get a number to aim for in hours and minutes that’s based on your own biology.  

You can learn more about how much sleep you need here and, how to know if you're getting enough sleep, and if you're one of the lucky ones with so-called short sleep syndrome here.

RISE users on iOS 1.202 and above can click here to view their sleep need.

Why Do I Sleep for More Than 8 Hours?

Consistently sleeping for more than eight hours? There are a few reasons why you may need this much sleep. 

Your Sleep Need is More Than 8 Hours 

As we explained above, your sleep need can easily be more than eight hours. If you find yourself needing to sleep for more than the recommended eight hours a night to feel your best, you may just be one of those people who needs more sleep. It’s genetics! 

The National Sleep Foundation says sleep needs vary for different age groups, too. While adults need seven to nine hours, newborns need 14 to 17 hours, preschoolers need 10 to 13 hours, and teenagers 8 to 10. 

When you don’t meet your sleep need, you’ll not only be hit with sleepiness during the day, everything from your creativity to your immune system, cognitive performance, overall physical health, and mental well-being will be impaired — so it’s an important number to pay attention to. 

Insufficient sleep also increases the risk of accidents and health problems like high blood pressure, obesity, and cardiovascular disease.

Essentially, for good health and wellness, and to feel your best each day, you want to be meeting your sleep need as much as possible, even if it’s more than eight hours.

You’re Paying Back Sleep Debt 

RISE app screenshot showing how much sleep debt you have.
The RISE app can work out how much sleep debt you have.

 If your sleep need is eight hours or less, but you’re finding yourself sleeping for longer, this may be your body catching up on recent sleep deprivation.

Sleep debt is the running total of how much sleep you owe your body over the last couple of weeks (in the RISE app we calculate it over your past 14 nights).  If you haven’t been meeting your sleep need recently, you’ll have built up sleep debt. And when your body gets the opportunity to, it’s going to want to pay back some of this debt and sleep for longer than your sleep need. 

RISE automatically works out how much sleep debt you’re carrying each day. We recommend keeping this number below five hours to feel your best. If your sleep debt is high, and your sleep need is eight hours or less, this debt may be the reason you’re sleeping, or getting the urge to sleep, for longer. 

RISE users on iOS 1.202 and above can click here to view their sleep debt.

Other Factors at Play 

If your sleep need is eight hours or less and your sleep debt is low, and you’re still sleeping for more than eight hours, there are a few reasons for this. 

Is 8 Hours of Sleep Too Much?

Just because guidelines state you can sleep for seven hours, that doesn’t mean eight hours of sleep isn’t necessary for some of us. In fact, it may not even be enough for you. Use RISE to find out unique sleep need to find out for sure. 

Eight hours of sleep may feel like “too much” if your sleep need is lower than this. However, experts agree it’s hard to sleep for longer than you need to. Your body may simply need more sleep if you’re stressed or ill, for example. 

In a 2021 paper, researchers analyzed two studies to determine whether you can sleep for too long. In one study, participants were given the chance to sleep for 14 hours a night and in the other, they could sleep for 12 hours a night and another four hours during the day. 

Participants slept for longer periods of time for the first one to three nights as they caught up on sleep debt. After this, however, no individual consistently slept for longer than 10 hours. 

The researchers concluded: “In response to the question: “Can I sleep too much?,” the answer is “No,” since “too much” implies sleeping longer than is biologically necessary.”

Why Do I Still Feel Tired After 8 Hours of Sleep?

If your sleep need is eight hours and you’re not paying back sleep debt, yet you still feel tired, there are a few culprits.

Sleep Efficiency 

Sleep efficiency is the measure of how long you spend in bed actually sleeping. It takes most people some time to drift off after they get into bed (also known as sleep latency) and we all wake up a few times during the night, even if we can’t remember doing so (also known as sleep fragmentation). 

So, eight hours in bed doesn’t equal eight hours of sleep. You may only be asleep for seven hours, for example. And if your sleep need is higher than this, you’ll inevitably feel tired. 

You can factor sleep efficiency into your night by adding some buffer time. If you have to get up at 8 a.m., and your sleep need is 8 hours 30 minutes, you can head to bed about nine hours before — say at 11 p.m. — to give yourself enough time to meet your sleep need. You can add more buffer time if it takes you longer to wind down and fall asleep. 

Good sleep habits (also known as sleep hygiene) can also help to keep your sleep efficiency high. This includes avoiding caffeine, exercise, and large meals too late in the day and taking time to do a relaxing bedtime routine.

The RISE app can guide you through 20+ sleep hygiene habits to help you fall asleep faster and wake up less often during the night. 

RISE users on iOS 1.202 and above can click here to set up their 20+ in-app habit notifications. 

Circadian Misalignment

Living out of sync with your circadian rhythm can also tank your energy levels. Your circadian rhythm is your body’s internal clock that runs on a roughly 24-hour cycle. It dictates when you feel awake and sleepy, amongst other things. 

You’ll be living out of sync with your circadian rhythm if you’re a shift worker, your sleep time doesn’t match your chronotype (think of night owls forcing themselves to be morning people), or you have social jet lag — when you go to bed later on the weekends than during the week, which about 87% of us do. 

You can sync up with your circadian rhythm by: 

  • Keeping a consistent sleep schedule, even on weekends. Regular sleep patterns also help to boost daytime energy levels.
  • Getting natural light exposure in the morning and throughout the day, but avoiding bright light 90 minutes before bed. 
  • Going to bed at the right time for you (check RISE for your Melatonin Window, the roughly one-hour window of time when your body’s rate of melatonin production is at its highest). Going to sleep at this time will help you fall asleep more easily. 

RISE users on iOS 1.202 and above can click here to set up a daily Melatonin Window reminder.  

Sleep Inertia 

RISE app screenshot showing times when your energy hits a peak and times when your energy is at a low.
The RISE app can predict how long your morning grogginess will last.

Sleep inertia is that groggy feeling you get just after waking up. This may make you wonder if you need more sleep than you’re currently getting, or if you’re getting poor sleep — but that may not be the case. Sleep inertia will feel worse after a lack of sleep or if you wake up during a deep sleep phase of your sleep cycle, but even when you get enough sleep, you’ll still feel it to some extent. 

Getting natural light, exercising, and drinking a cup of coffee can help to shake off this grogginess. You can learn more about how to get more energy in the morning here. 

You can also check RISE to see a prediction of how long sleep inertia will last for each day, so you know when you can expect your energy levels to pick up. 

Other Factors at Play 

Beyond things like circadian misalignment and sleep inertia, you may feel tired after getting eight hours of sleep due to: 

  • A sleep disorder like narcolepsy or sleep apnea. 
  • Medical conditions like anemia and chronic fatigue. 
  • Side effects from medications. 
  • Sleep debt from previous nights impacting your energy levels — you may have had a good night’s sleep, but you’re still tired the next day as any or all of the last 13 nights were insufficient.

You can learn more about why you’re always tired here. You should speak to a health care professional if you think a sleep problem or medical condition is the reason for your tiredness.  

Find Out the Ideal Amount of Sleep for You 

It can be confusing to know how much sleep is enough when the general recommendation varies by two whole hours. We’re told again and again to get eight hours of shut-eye, but don’t just blindly follow this advice. 

Take the guesswork out of it and use the RISE app to find out your individual sleep need. Once you know what your body needs, you can start aiming for this number each night, knowing it’s enough for you. 

You can also use the app to keep track of your sleep debt and stay in sync with your circadian rhythm — two things will maximize your energy levels and help you feel your best day after day. Plus, stay on top of 20+ sleep hygiene habits for better sleep.


Is 8 hours of sleep enough?

Eight hours of sleep is enough if that is what your sleep need is. If your sleep need is higher, you have sleep debt, you’re ill, or stressed, however, you’ll need more than eight hours.

Is 8 hours of sleep good?

Eight hours of sleep is not too much if this is what your body needs. Even if your body needs less sleep, you may still need eight hours if you’re ill, stressed, recovering from intense exercise, or you’re catching up on lost sleep. Plus, sleep researchers say it’s impossible to sleep “too much,” or longer than biologically necessary.

Is 8 hours of sleep enough for a student?

Eight hours of sleep is enough for a student if that’s their sleep need. According to the National Sleep Foundation, school-aged children need nine to 11 hours of sleep, teenagers need eight to 10, and young adults and adults need seven to nine. However, how much sleep a student needs will all depend on their unique sleep need and how much sleep debt they have.

Is 8 hours of sleep a myth?

8 hours of sleep is both a myth and not a myth: There’s evidence to suggest most adults need between 7.5 and 9 hours of sleep a night, so 8 hours might be your sleep need. However, everyone’s sleep need is unique! It is a myth that everyone will feel and function at their best with 8 hours of sleep. Instead, getting only 8 hours of sleep when you need more, will leave you with sleep debt and a lack of energy.

About Our Editorial Team

Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Chester Wu, MD, Rise Science Medical Reviewer
Our Editorial Standards
We bring sleep research out of the lab and into your life. Every post begins with peer-reviewed studies — not third-party sources — to make sure we only share advice that can be defended to a room full of sleep scientists.
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Updated Regularly
We regularly update our articles to explain the latest research and shifts in scientific consensus in a simple and actionable way.

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About Rise
Rise is the only app that unlocks the real-world benefits of better sleep.

Instead of just promising a better night, we use 100 years of sleep science to help you pay down sleep debt and take advantage of your circadian rhythm to be your best.

Over the past decade, we've helped professional athletes, startups, and Fortune 500s improve their sleep to measurably win more in the real-world scenarios that matter most.

Rise Science is backed by True Ventures, Freestyle Capital, and High Alpha; investors behind category winners Fitbit, Peloton, and Salesforce Marketing Cloud.

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