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Sleep calculator: Find your optimal bedtime

25/06/2021 6 MIN. READ Mirko Berger
25/06/2021 6 MIN. READ Mirko Berger

Perhaps you’ve already felt that slight panic as you lie in bed and glance one last time at the clock: your mind starts racing because you’ve just calculated how many hours until your heartless alarm is set to ring. It can be a very sobering experience, especially when you realise that fateful moment is only a few hours away. It’s dispiriting to go to bed with this feeling hanging over your head. In fact, in a worst-case scenario, you might end up not being able to fall asleep at all. 

Insufficient sleep can also have a negative impact on your health. This is why we highly recommend you use our sleep calculator to determine your ideal bedtime. The calculator helps you adjust your evening routine and plan in advance when to get to bed and turn the lights out. In order to get the most out of it, however, it’s important to be aware of the factors that affect our bedtime and sleep.

Factors to consider when deciding your bedtime 

Sleep is a very individual thing, and everyone has different sleep-related needs. But one thing is for sure: getting enough sleep is essential for our survival and has a major impact on our overall sense of wellbeing. Our sleep calculator takes a number of factors into account, for example, the fact that human beings have different sleep cycles. It also considers certain individual characteristics, such as your age and sleep chronotype. In order to be able to understand why a specific bedtime might be right for you, let’s take a closer look at the individual factors involved.

A healthy amount of sleep

Because every person is unique, it’s impossible to make a sweeping statement about how much sleep is healthy. Your genes pretty much determine whether you’ll need 7 hours of sleep to feel well-rested or whether you’ll still feel tired even after 8 hours of shut-eye. The National Sleep Foundation, a US-based not-for-profit research organisation, has nevertheless issued some general recommendations that include the assertion that sleeping less than 7 and more than 9 hours over the long term is not healthy for most adults.

Still, it’s more or less up to you to figure out whether you tend to need only 7 or, in fact, 9 hours of sleep. The key issue here has less to do with how many hours you sleep and more with how you feel when you wake up. After a night of getting an adequate amount of sleep, you should feel alert and well-slept. Most of us know what it’s like to wake up all on our own a couple of minutes before our alarm: What a great feeling! It also means that you just got your ideal amount of sleep. No matter what, we recommend that you observe yourself and your needs, and always listen to your body.

If you don’t get enough sleep over an extended period of time, it can make you more susceptible to certain illnesses, including high blood pressure, obesity, type 2 diabetes and a faulty immune system. However, getting too much sleep can be just as bad, as demonstrated by a recent French study involving 24,671 test persons between the ages of 15 and 85. In fact, the study found an increased tendency towards mental illness and obesity among people who sleep too much.

Sleep cycles

When we sleep, we pass through several different sleep cycles. In turn, these cycles consist of different sleep phases, which include the falling-asleep phase, the light-sleep phase, the deep-sleep phase and the REM-sleep phase. The first three stages can also be referred to as the non-REM sleep phases. 

The abbreviation REM stands for “rapid eye movement” and designates the phase in which our eyeballs move back and forth quickly and visibly, even though our eyelids are closed. Since the REM phase is the phase in which we often dream very intensely, it is also called the “dream phase”. It usually lasts only a couple of minutes, and when it’s over, we either wake up very briefly or drift straight back into a light-sleep phase.

The ideal time to wake up and actually get up is in those moments between the REM phase and the beginning of a new sleep cycle. If our alarm clock wakes us up in the middle of a deep-sleep phase, we might feel utterly exhausted, no matter how many hours of sleep we’ve had. Our sleep calculator also takes into account the fact that a sleep cycle usually lasts an average of roughly 90 minutes.

Your sleep chronotype

Have you ever heard of the owls and the larks? We’re not talking about the birds in the trees but different sleep chronotypes. Every person has a genetically determined internal clock determined by their chronotype.

Researchers usually distinguish between three different categories of chronotypes. First up are the early birds – also called the “larks” – who have no problem getting up in the morning, but get tired in the early evening. Next up are the night people – also called the “owls” – who only really get going in the evening, but find it difficult to get out of bed in the morning. And, finally, there are those who are somewhere in between the larks and the owls. Your chronotype has a direct influence on the time at which it’s most beneficial for you to go to sleep.  

Your age

As a baby, you probably spent half the day sleeping. As a teenager, sleep probably became less important to you. And when we become older adults, we require even less sleep. According to the National Sleep Foundation, newborns need between 14 and 17 hours of sleep, which then gradually decreases to 8 to 10 hours by the time you enter your teenage years. For young adults, 7 to 9 hours are recommended, and for older adults, the recommendation is 7 to 8 hours.

This is why age is an important factor when using the sleep calculator, as it influences when you should go to bed.

How fast you fall asleep 

The final key factor involved in calculating your perfect bedtime is how fast you fall asleep. As we all know, getting under the covers and turning out the lights doesn’t mean we automatically drift off to sleep, as nice as that would be! 

Once again, the average time a person needs to fall asleep is unique to each of us. And this is something that’s very hard to measure. After all, if you’re constantly checking your watch to see how long it’s been since you turned out the light, you’ll likely find it hard to fall asleep naturally. This is why it’s best to calculate using the average time it takes a person to fall asleep, which is around 15 minutes. If you feel like it takes a bit longer in your case, you can simply adjust the time in the sleep calculator – or see if you can reduce it with help from our tips for falling asleep. Good sleep hygiene can also have a positive impact on how quickly you fall asleep. 

The formula for calculating your ideal bedtime

Drum roll, please! The moment has arrived and we’re ready to calculate your optimal bedtime. The sleep calculator takes a number of variables into account – and you should take a moment to define these before you proceed:

  1. a = the time you want to wake up at
  2. b = your ideal number of hours of sleep
    Please note: Choose between 6 hours, 7.5 hours or 9 hours – it’s also important that you take into account your age and personal experience when choosing this number.
  3. c = how long it takes you to fall asleep (the average is 15 minutes)

As soon as you’ve established these three values, you’re ready to calculate your perfect bedtime (x) using the following formula: 

x = a - b - c

In order to determine the ideal number of hours of sleep you should be getting, just try out the sleep calculator for the next several days and vary the numbers a bit. If you’re still feeling tired in the morning, even after you’ve technically had enough sleep, it’s possible that you belong to the chronotype known as the “owl”. In that case, your performance levels will simply not be very high in the early morning hours. If possible, you should try to adjust your wake-up time rather than focussing on how many hours of sleep you get.

We hope you have lots of fun calculating your ideal bedtime! Sleep well! 

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