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Sleep Calculator: Get the Hours Needed To Wake Up Refreshed

Work out how much sleep you need and how much you really get each night with the RISE app. Then take steps towards waking up feeling more refreshed.
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Chester Wu, MD, Rise Science Medical Reviewer
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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.
Woman fast asleep with cellphone nearby that calculates her sleep

There are a lot of sleep calculators out there. Some take your preferred wake-up time and count back five 90-minute sleep cycles, others just take off eight hours. But sleep, and how much of it we need to feel our best, is more complicated than that. 

There are many factors that go into working out how much sleep you need, when you should go to bed and wake up, and how you can wake up feeling refreshed.

Below, we’ll dive into the problem with many sleep calculators and how the RISE app can help. 

Why Should I Calculate How Much Sleep I Need?

The National Sleep Foundation says healthy adults should get between seven and nine hours of sleep a night. But that doesn’t mean you should simply aim for an amount between those two numbers and be done with it. 

These guidelines are exactly that: guidelines. And experts say that while it’s a good starting point, guidelines don’t take into account individual sleep needs. 

Your sleep need is the amount of sleep you need each night. It’s determined by genetics, just like height and eye color, so it’s unique to you and it’s set from early adulthood. 

One study suggests the average sleep need is 8 hours 40 minutes, plus or minus 10 minutes or so, but 13.5% of the population may need 9 hours or more sleep a night. So, simply aiming for seven hours because it’s within the seven-to-nine-hour suggestion could leave you getting much less sleep than you need to feel and perform at your best. 

A 2018 paper looking into the ideal sleep duration said: “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.” 

The researchers added that these guidelines often come from observational studies and self-reported data. Not only is it difficult to accurately measure how much sleep you’re getting by yourself, the guidelines were derived from how much sleep people were getting, not how much they actually need. 

And all too often the amount of sleep you’re getting is less than you need. Our brains can adapt to how much sleep we get, so we might be feeling totally fine when really we need more sleep to reach our full potential.

When you don’t meet your sleep need, your productivity, creativity, and mental well-being decreases, while your risk of things like high blood pressure, heart disease, and obesity increases — so it’s important to know your individual sleep need. 

By using a sleep calculator like RISE, you can stop relying on guidelines and guesswork, and find out your actual sleep need once and for all.

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

How Do I Calculate How Much Sleep I Need?

Now we’ve established that it’s worth calculating your individual sleep need, rather than relying on general guidelines, here’s how to do it. 

The Manual Way 

You can work out how much sleep you need by waking up without an alarm clock for at least a week and keeping track of how long you naturally sleep for. This method is tricky for a few reasons, though. 

Firstly, you might sleep for longer than usual as your body is catching up on sleep debt. This is the sleep you owe your body. In the RISE app, we measure it over the last 14 nights. 

So, if your sleep need is 8 hours 10 minutes, but you’ve only been getting 7 hours a night recently, you’ll have built up sleep debt. When your body gets the chance (like when you don’t set an alarm), it’ll want to oversleep your sleep need to catch up on this sleep deprivation. 

Without a sleep calculator, it’s hard to know if you’re sleeping for longer than usual because that’s your sleep need or because your body is paying down sleep debt. 

Secondly, it’s difficult to accurately work out how much sleep you get by yourself. 

For example, eight hours in bed doesn’t equal eight hours of sleep. You need to think about sleep efficiency, which is the measure of how long you spend in bed actually sleeping. This is made up of sleep latency (how long it takes you to fall asleep) and sleep fragmentation (how often you wake up during the night). 

Plus, you might wake up feeling groggy — this is natural and it’s called sleep inertia — and think this means you haven’t had enough sleep. 

Thirdly, and perhaps most importantly, most of us simply don’t have the luxury of not setting an alarm — especially for a whole week! The only time you might be able to try this method is when on vacation. 

The Accurate Way 

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

You can use a sleep calculator to work out your individual sleep need — and this method is much more accurate. 

However, don’t just turn to any old sleep calculator. You need one that will actually work out your sleep need, rather than relying on those guidelines we spoke about earlier. 

The RISE app uses a year’s worth of your phone use behavior and proprietary sleep-science-based models to work out your sleep need and give you a number in hours and minutes. 

The app can also work out how much sleep debt you’re carrying, so you know if your body wants to temporarily sleep for longer. 

You can learn more about how much sleep you need here. 

How Do I Calculate How Much Sleep I Get?

Once you know your sleep need, it’s time to work towards getting it each night. Sleep calculators can also help you accurately work out how much sleep you’re getting.

We’ve already covered some of the problems of trying to work out how long you slept for by yourself. They include: 

  • Thinking time in bed is the same as time asleep.  
  • Not being able to calculate sleep efficiency – do you really know down to the minute how long it took you to fall asleep last night? 
  • Overestimating how much sleep you got — it’s easy to bump this number up, especially if you want to feel better about your lack of sleep. 

Study after study has shown that self-reported sleep data isn’t accurate. In fact, a 2021 study measuring participants’ sleep patterns found the average agreement level between self-reported sleep and sleep measured by a device was only 57%. 

Even if you do use a sleep calculator or fitness tracker, it’s easy to get caught up in different sleep scores that don’t really matter. Experts don’t have an agreed-upon definition for sleep quality, for example. 

And while checking out your complete sleep cycles and time spent in different stages is interesting, it’s easy to think deep sleep is the most important stage to get, light sleep isn’t very good, and rapid eye movement sleep (REM sleep) is just for dreaming — when really, all stages are needed for optimum health and maximum energy. 

In reality, you don’t need to know how long you spent in non-rapid eye movement sleep (non-REM), how “good” of a sleeper you are, or even know your sleep health score — you just need to know your sleep debt. When you know how much sleep debt you have, you’ll know if you’re meeting your sleep need each night or if you need to catch up on lost sleep. 

The RISE app uses phone motion-based sleep detection to work out when you fall asleep, when you wake up during the night, and when you get up in the morning.

This will give you an accurate measure of how much sleep you get each night. You can also add in any naps you take during the day, so your sleep debt is more accurately measured. 

Heads-up: Sleep debt is the most important score to keep an eye on as it’s the single biggest thing determining how much energy you have each day.

RISE takes into account your nightly sleep times and any naps to give you a number, and keeps track of sleep debt as you work to pay it back through oversleeping your sleep need at night or taking well-timed naps. 

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

Dive deeper:

What Are the Best Times to Go to Sleep and Wake Up?

RISE app screenshot showing your melatonin window which can tell you the best time to go to sleep.
The RISE app can tell you the best time to go to bed.

Looking for the best times to go to sleep and wake up? Sleep calculators often just count back a set number of hours from your desired wake-up time, but to really maximize your energy levels, there’s more to it than that. 

It starts by finding out your sleep need. Use RISE to get a number to aim for each night. 

Once you know how long you need to sleep for, you need to add some buffer time to take into account sleep efficiency. Add 30 minutes to an hour onto your sleep need to find out how long you should be in bed. How long you add depends on how quickly you fall asleep, and how long you’re awake for during the night.

Don’t worry if you don’t fall asleep immediately, falling asleep within 10 minutes may actually be a sign of sleep deprivation. It’s normal to take 10 to 20 minutes to fall asleep. Taking longer than 20 minutes may be a sign of stress, a medical condition, or poor sleep hygiene (more on how to improve this to improve your sleep efficiency soon). And repeatedly taking longer than 30 minutes to fall asleep could be a sign of a sleep disorder like insomnia.

Once you know how long you should be in bed for each night, it’s time to find out the best times to do this.

You need to think about your chronotype, or whether you’re an early bird, night owl, or somewhere in between. You should try to honor your chronotype and go to sleep and wake up when your body naturally wants you to. 

You should also think about your social clock, or the commitments you have — such as the time you need to start work or get the kids up for school. If your ideal wake time doesn’t fit with your lifestyle, you can reset your circadian rhythm (your body clock) and shift it earlier. 

You can also check RISE to see your Melatonin Window, the roughly one-hour window of time when your body’s rate of melatonin production is at its highest. As melatonin helps prime your body for sleep, this is the ideal time to head to bed. 

The app also shows you your “Wake Zone,” or the best time to wake up, too, based on your sleep need and body clock. 

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

You can learn more about how to get on the right sleep schedule for you and stick to it here.  

How Can I Get Enough Sleep Each Night?

Looking at data can be interesting, of course, but most of us don’t just want to know how much sleep we need, we want to actually get that amount to start enjoying more energy. 

RISE goes beyond traditional sleep calculators to help you actually get the sleep you need each night to feel your best each day.

Firstly, it works out and keeps track of your sleep debt, the biggest thing determining your energy levels. We recommend keeping sleep debt below five hours to feel and function your best. 

If you’ve got a lot of sleep debt, you can pay it down by: 

Secondly, it guides you through 20+ sleep hygiene habits to help you get a good night’s sleep. This includes things like:

RISE tells you when to do these sleep hygiene behaviors at the right time for you based on your circadian rhythm each day, making them more effective. 

Finally, check RISE for your Melatonin Window each night and aim to go to sleep during this one-hour window for a better chance of falling and staying asleep. 

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

Use a Sleep Calculator That Actually Works 

Whether you’re looking to find out how much sleep you need, the ideal time to go to bed, or you want to track how long you sleep for each night the RISE app is the accurate way to do it. The app works out your sleep need down to the minute.

Forget about sleep cycle calculators and tracking the stages of sleep, and focus instead on the sleep score that makes the biggest difference: sleep debt. RISE works this out for you and keeps track of it as you work to pay it back.

Plus, the app helps you get better sleep by guiding you through 20+ sleep hygiene habits, so you don’t just know how much sleep you need, you can actually begin getting it. 

How much sleep is right for you?


How do I calculate how many hours of sleep I need?

You can calculate how many hours of sleep you need by waking up without an alarm for at least a week and keeping track of your sleep times. The more accurate way, however, is by using the RISE app. RISE uses your phone use behavior and proprietary sleep-science-based models to work out how much sleep you need and it gives you a number in hours and minutes. You can learn more about how much sleep you need here.

How many hours of sleep did I get?

You can keep a manual log to work out how many hours of sleep you get each night, but studies show this isn’t very accurate. Use the RISE app instead, which monitors your sleep times, including how long you were awake for during the night. You can also add in your nap times for a better measure of your sleep debt, or how much sleep you owe your body.

Sleep calculator app

RISE is a sleep calculator app that works out your individual sleep need, or how much sleep you need each night, and your sleep debt, or how much sleep you owe your body. The app also shows you the best time to go to sleep and wake up based on your body clock.

Sleep calculator by age

According to the National Sleep Foundation, different age groups need a different amount of sleep. Newborns need 14 to 17 hours of sleep, infants need 12 to 15, toddlers 11 to 14, preschoolers 10 to 13, school-aged children 9 to 11, teenagers 8 to 10, and adults 7 to 9. Older adults need the same amount of sleep as younger adults, despite what guidelines say, but it may be harder to get. Rather than relying on generic guidelines, however, you can use the RISE app to find out your individual sleep need down to the minute.

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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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