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Sleep Cycles: What Are They & How Many Do I Need? [Tool]

Some need to work more on getting their sleep than others

Do you feel tired when you wake up or during the morning hours?

For me, it was the feeling of it taking forever to "boot-up" and shake off that drowsiness that made me dive into the subject of sleep.

I wanted to know what I was doing wrong.

I found out that feeling tired and "non-booted" after a night's sleep might be because of the simple fact that you don't get enough hours of sleep.

That's easy enough to fix right? Just go to bed earlier and sleep longer!

But it turned out that wasn't the case for me.

Read on to learn about sleep cycles and how important they are for your well-being!

We also have a sleep cycle tool that can help you figure out when to go to bed. Follow the link in the table of contents below.

How Learning About Sleep Cycles Helped Me

What I figured out was that I was waking up in the middle of a sleep cycle. That’s when I really got interested in learning more about sleep and what sleep cycles are all about.

Sleep cycles are periods of about 90 minutes where our body and mind go through a sort of cleansing and rebooting of all the systems. And research tells us that we need many of them, not less than 5 per night, to be fully rested and refreshed (adults).

But what I was doing wrong wasn't that I usually got less than 5 sleep cycles per night but that I'd set my alarm clock to wake me up in the middle of sleep cycle 6 for the most part and some days even in the middle of sleep cycle number 5.

In this article I want to explain the magic of sleep cycles and also help you to, with our very own sleep cycle tool, figure out when you should go to bed so that you can avoid waking up in the middle of one.

Armed with this knowledge (and our tool) you'll be able to take control of your sleep and figure out a way to wake up refreshed and "boot-up" faster every morning.

Normally we sleep for about a third of our lives. Let's not go around feeling half-a-sleep all of the mornings as well!

What Is A Sleep Cycle?

Every sleep cycle is valuable. Don't interrupt them.

During the night, you alternate between sleep depths.

I like to think about these depths or different stages as going from shallow to deep sleep and back again.

Research tells us that a normal night of sleep is divided into sleep cycles.

A sleep cycle begins with you gradually descending for about 20 minutes into a deeper sleep, from stage 1 to stage 3 or 4.

You can read about the stages further down in the article.

After stage 4 you usually enter an episode of REM sleep. This is the stage where your body is the most active during sleep.

This is also where its believed you dream the most.

The first sleep cycles during the night consists mainly of deep sleep with less amount of REM, while the sleep cycles during the later parts of the night include more REM sleep.

During a lifetime, the need for sleep varies. Children need to sleep a lot more than adults and elderly. Children experience REM sleep a lot more as well.

What Are The Different Stages Of The Sleep Cycle?

Since the early 20th century, human sleep has been described as a succession of five recurring stages, sleep cycles, that are comprised of four NREM stages and the REM stage.

We need to cover the difference between NREM and REM sleep before we go through each of the 5 stages in the sleep cycle in more detail.

What is NREM and REM sleep?

The five different stages of sleep are divided in NREM and REM sleep. But what are they?

NREM

NREM means Non-Rapid Eye Movement.

The NREM sleep is divided into four stages, where stages 1 and 2 are the most superficial form of sleep and stages 3 and 4 are deep sleep.

The deep sleep stages of 3 and 4 are the ones that gives you the feeling of being rested when you wake up.

A person who’s recently fallen asleep, in the first stage and wakes up within half an hour usually doesn’t feel like he’s slept at all.

REM

REM means Rapid Eye Movements. It got its name because of the rapid eye movements seen in sleeping people during REM sleep.

REM sleep is the fifth stage of the sleep cycle. The exact function of the REM sleep is uncertain.

When you enter REM sleep you don’t remain in that stage for the remainder of the night but, rather, cycle between stages of NREM and REM throughout the night.

NREM sleep constitutes about 75 to 80 percent of total time spent in sleep, and REM sleep constitutes the remaining 20 to 25 percent. (source)

Sleep Cycle Stage 1: Drifting between wakefulness and sleep

Stage 1 is the transitional stage between wakefulness and sleep.

The first stage begins when you close your eyes in bed, you shift in and out of consciousness, and loose your sense of time and place.

As you are still partially awake in this stage, it’s still very easy to wake you up.

This is the stage where you may suddenly feel like you are falling and jolt awake. This is called hypnic myoclonia or hypnic jerk. (source)

If you awaken from the first sleep stage, you might not even be aware that you were sleeping.

Sleep Cycle Stage 2: You’re asleep and your body relaxes

Stage 2 is a phase of light sleep. Throughout the night and several sleep cycles, you’ll spend approximately 50 percent of your time in this second stage.

During the second stage, the brain activity slows down from waking levels.

The body also relaxes physically, your heart rate and your breathing decreases.

Stage 2 is a stage where you’re asleep, but not in deep sleep.

It’s still easy to wake from this stage.

Sleep Cycle Stage 3: Descending into deep sleep

Stage 3 is the first phase of deep sleep, also known as slow-wave sleep.

Normally it takes about 30 minutes to reach this stage for the first time after falling asleep.

You can say that stage 3 is like the stepping stool to the deep sleep. Stage 3 lasts only a few minutes and constitutes about 3 to 8 percent of sleep.

During this phase of sleep, brain waves slow down considerably.

Your heart rate and breathing slow down. Also, your blood pressure lowers, and your muscles relax.

The understanding of sleep cycles can help you sleep better!

Sleep Cycle Stage 4: Important for your immune system

Stage 4 is the second stage of deep sleep. The body is now so relaxed and ready for restoration and recovery.

It's very difficult to wake someone during stages 3 and 4.

In stage 3 and 4 you have no recognizable eye movement or muscle activity.

This stage is a critical time for physical restoration.

Repair occurs at the cellular level, restoring strength and function to tissue, muscle, and organs throughout the body.

This stage is also very important for restoring function to the immune system.

People awakened during deep sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up.

Some children experience bed-wetting, night terrors, or sleepwalking during deep sleep.

This stage length is depending on age. Older people experience less time here while younger people will experience more.

Sleep Cycle Stage 5: REM sleep

You reach REM sleep for the first time approximately 75 minutes into the night and the initial cycle, may only last 1 to 5 minutes.

The first few cycle's REM periods are quite short. They get progressively longer throughout the night. (source)

During REM sleep, the brain increases its activity levels significantly compared to the other sleep phases.

When we go into REM sleep, our breathing becomes more rapid, irregular, and shallow, our eyes jerk rapidly in various directions, and our limb muscles become temporarily paralyzed. Our heart rate increases and our blood pressure rises.

Most dreams occur during REM sleep. If you wake up with an awareness of having been dreaming, you likely awoke from REM sleep.

REM sleep is a critical phase of sleep for learning and memory, a time when the brain processes and stores information. (source 1, source 2)

Every Stage In A Sleep Cycle Has A Purpose

At each stage in a sleep cycle, your body is occupied in a process of repair and rejuvenation.

It's restoring stamina, strength, and function to prepare for the day ahead.

The restorative processes of sleep are physical, including cell repair, hormone regulation, and protecting healthy immune system function.

Sleep doesn’t only restore us physically, but also mentally, aiding in the processing of memory, emotion, and learning.

All stages of sleep are important.

It’s the balance of time spent in each sleep cycle stage that’s critical to feeling fully rested and refreshed, and to have the mental and physical energy to meet the day to come. (source)

Dreams During The Night

We typically spend about 2 hours each night dreaming.

A lot of research is being done around the topic of dreams, but scientists are still not sure how or why we dream.

They do know that dreams almost always occur during REM sleep. And, when a dream does occur in the deep sleep, stage 3 or 4, it’s usually a nightmare.

Dreaming is believed to help you process your emotions. People suffering from stress or anxiety are more likely to have frightening dreams.

Sleep Related Form Of Memory Loss

When someone awakens after sleeping just for a few minutes they are usually unable to recall the last few minutes before they fell asleep.

This sleep-related form of amnesia is the reason people often forget the conversations they had in the middle of the night or just before falling asleep.

It also explains why we often don’t remember our alarms ringing in the morning if we go right back to sleep after turning them off. (source)

How Many Sleep Cycles Do I Need?

It’s important to sleep whole cycles to be able to fell rested.

A normal sleep cycle lasts for about 90 minutes and we need to get through about 5 or 6 of them during one night.

This means that it’s possible to calculate quite precisely when we need to go to bed to wake up rested at a certain time.

You can either choose to do a calculation based on what you set the alarm clock on and get suggestions on what time you should go to bed.

Or the other way around. If you go to bed now, what time should you set the alarm on?

Waking up in the middle of a sleep cycle can make you feel chubby and tired.

By setting your alarm so that you wake up between two sleep cycles you are more than likely able to start the day by feeling well-rested.

Your need for sleep varies with age, the older you get the less sleep you need

Newborn, 0 to 3 months

Newborn and Infants need the most sleep, from 9 to 11 sleep cycles (about 13 – 17 hours of sleep per night).

Newborns don't have an established circadian rhythm; it isn't established until they're 2-3 months old.

Infants, 3 months to 1 year

Infants usually sleep in several phases throughout the day, sleeping from 2.5 to 4 hours at a time.

By around 12 months, infants start sleeping more at night.

Toddlers, 1 to 3 years

The need for sleep varies with age but the need for closeness and love remain the same!

Toddlers aged 1 to 3 years need about 8 to 9 sleep cycles per night (between 12 to 14 hours).

Preschool, 3 to 5 years

Preschool aged children need about 8 to 9 sleep cycles each night (between 11 to 13 hours).

School Age, 5 - 13 years

School aged children between the ages 5 – 13 needs 7 to 8 sleep cycles (between 10 – 12 hours of sleep per night)

School-age children that aren't sleeping enough can be difficult as tired kids tend to not slow down, they speed up.

They often try resist going to bed at night, even though they're tired.

Teenagers, 14 - 17 years

Teenagers between the ages 14 – 17 needs 6 to 7 sleep cycles (about 9 – 10 hours of sleep per night).

The circadian rhythms shift after puberty, making teens want to go to bed after 11 pm and wake up later.

During the week most need to go up earlier than they want which leads to that teens don’t get enough sleep.

As teens often are sleep-deprived during the week, they sleep more on the weekends.

Adults, 18+

Adults from the age of 18 and up require less sleep, 5 to 6 sleep cycles, (between 7 – 9 hours per night). (source)

Table 1. Recommended full sleep cycles per night divided by age group.
Age GroupSleep CyclesEq. Hours
Newborn (0 - 3m)1015 hours
Infant (3m - 1y)913.5 hours
Toddler (1 - 3)812 hours
Preschool Age (3 - 5)812 hours
School Age (5 - 13)710.5 hours
Teenager (13 - 18)69 hours
Adult (18+)57.5 hours

It takes about 15 minutes on average for a person to fall asleep. Add 15 minutes to the eq. hours in table 1 if you want to calculate when to go to bed.

You can also use our sleep cycle tool below.

Our Sleep Cycle Tool - Try It Out!

With the tool below you can easily see when to go to bed so that you can wake up a certain time feeling as refreshed as possible.

You can also use the tool the other way around and figure out when to wake up if you go to bed at a certain time.

The yellow pie-piece indicates the first 15 minutes that most need to fall asleep after going to bed.

The green pie-pieces are all 90 minutes long to indicate one sleep cycle.

We’ve also made their color go from light green to a more darker green to hint that the more sleep cycles you get per night the better off you’ll be in the long run.

Sleep Cycle Tool - When Is The Optimal Time To Go To Bed?

Select Age and Rotate Dial With Buttons Below

Selected Age: Adult

Beware that even if it’s entirely possible to get only a few cycles worth of sleep one night and still wake up feeling refreshed it’s not something that’s recommended you do every night.

Your health and well-being depends on you getting enough sleep.

Please share this article!

Conclusion: Sleep is important for your health. Understanding sleep cycles will help you sleep better!

Sleep is very important for us. We can't function properly without getting enough quality sleep.

Understanding and using your knowledge of the sleep cycle might give you better sleep.

Usually, a night's sleep goes through five stages: 1, 2, 3, 4 and REM (rapid eye movement) sleep.

These stages progress cyclically from 1 through REM then begin again with stage 1.

The first sleep cycles each night have relatively short REM periods and long periods of deep sleep but later in the night, the REM periods lengthen and the deep sleep periods decrease.

If you’re having trouble falling asleep at night, there are effective natural sleep aids that can help. We've written an article about natural sleep aids if you want to know more.

Goodnight and sweet dreams!

Frequently asked questions about Sleep Cycles

What are sleep cycles?

During a nights sleep, you alternate between sleep depths, different stages of sleep. Each cycle through the different stages of sleep is called a sleep cycle. Sleep cycles are made up of 5 different stages. A normal sleep cycle for an adult is about 90 minutes long and contains all stages of the sleep cycle.

How many hours is a full sleep cycle?

A full normal sleep cycle from stage 1 to REM takes about 90 minutes to complete. An adult typically needs to complete at least four to six sleep cycles per night. That equates to between 6 to 9 hours of sleep per night.

Is REM deep sleep?

No, Rapid Eye Movement (REM) is the final stage (5) of a sleep cycle. It's very different from the deep sleep stages 3 and 4. In REM sleep your body is much more active relative to deep sleep.

When should you wake up in the sleep cycle?

By waking up between two sleep cycles you’re often able to start the day by feeling well-rested. Waking up in the middle of a sleep cycle can make you feel chubby and tired even though you’ve had enough sleep. You can use our Sleep Cycle Tool to figure out when you should go to bed and wake up.

Article written by,

Sara Niemelä

co-founder Care Omnia, Head Content Creator

Licensed Practical Nurse (LPN), University Diploma in Educational Information and Communication Technology, Bachelor of Science in Social Work