Sleep time Calculator

It takes the average person 15 minutes to fall asleep, try sleeping 10-20 minutes before one of the recommended times provided by the sleep cycle calculator.

Its recommended to sleep through 4 – 6 cycles each night, these key sleep cycles are listed in the table above.

What is the Sleep Cycle? Explore 5 Cycles of Human Sleep

Sleep is an essential factor for human health. Human sleep is divided into some certain stages; at each stage, the body has its own characteristic activities. Have you ever wondered how your body works while you are sleeping? Let’s discover this in the following post!

1. What is the sleep cycle?

Sleep has been a topic of concern for scientists for such a long time, maybe decades ago. Researchers suppose that some body parts are still active when we sleep, and these activities occur unevenly at different stages of sleep.

Through the process of observing human sleep, scientists realized that sleep is divided into certain stages; during each stage, the body parts take on different roles. These stages take place in a sleep cycle and repeat nightly. 

2. Stages of the sleep cycle

There are two kinds of sleep cycles, which are NREM (Non Rapid Eye Movement) and REM (Rapid Eye Movement), which occur during the sleeping time of everyone.

2.1. NREM sleep

NREM sleep is non-rapid eye movement sleep, or restful sleep, which is divided into 4 stages: transition to sleep, light sleep, deep sleep and intense deep sleep.

2.1.1. Transition to sleep

The transition to sleep is the movement between waking and sleeping states, which usually takes place in a short time of 5 to 10 minutes. People are often in a state of lethargy and drowsiness with slow breath, regular heart rate and low blood pressure. During this time, we are easily awakened and it is difficult for us to fall back to sleep. 

Some people even experience sudden convulsions if they are awakened during the transition to sleep. The feeling is like when you are concentrating on your duty and someone taps on your shoulders and startles you. Besides, during this stage, the human brain will release theta waves, or intense slow brain waves. 

2.1.2. Light sleep 

The light sleep stage lasts about 20 minutes. During this stage, the brain waves slow down, its amplitude is larger, the heart rate and breathing rate slow down and the eyes don’t move. Sometimes, rapid waves also appear inside the brain (which is called the sleep spindle). Therefore, sleepers are often lethargic and unconscious during the light sleep stage. 

In addition, the US National Sleep Foundation also judges that this stage accounts for 50% of total sleep time.

2.1.3. Deep sleep 

This is the transition period between light sleep and intense deep sleep. Deep sleep only takes 10% of the sleeping time of humans. This stage occurs after you start sleeping for 30 to 40 minutes, and this can last longer in the young and shorter in the elderly. It is relatively difficult to wake the sleepers up without shaking their body or making loud noises around them. 

During the deep sleep stage, delta brain waves are produced and this process occurs more slowly than that one in light sleep. The body temperature, breathing rate, heart rate and blood pressure all decrease, and the musculoskeletal system also sags. 

2.1.4. Intense deep sleep

The intense deep sleep stage is extremely important since it helps the body to rest and completely relax in order to regenerate energy after we wake up. 

The intense deep sleep accounts for 20% of the total sleeping time. The muscles of the arms, legs and eyes are completely immobile; the body temperature, heart rate, breathing rate and blood pressure all reduce to a minimum. If we are awakened during this stage, we often feel groggy, dizzy and disoriented. It takes a few minutes for our body to fully awake. 

2.2. REM sleep

REM sleep, also known as rapid eye movement sleep, or dream sleep, accounts for about 20% of the total sleep time. During this stage, the brain will be active and dreams often appear. If you are awakened, you can remember the dreams and myths happening in your mind during your sleep. 

During REM sleep, our eyes also move faster than in other stages; the heart rate, breathing rate, body temperature and blood pressure also increase. However, the body is barely able to move since the major muscles are almost paralyzed. At the end of the REM stage, we often wake up temporarily and quickly return to a sleep cycle lasting till the next morning. 

For newborn babies, the duration of NREM and REM sleep is relatively even with a ratio of 50/50. For children from 5 years old, REM sleep accounts for 30% and NREM sleep accounts for about 70%. For adults, the ratio is 80/20 because adults spend very little time dreaming.

Several studies have shown that increasing REM sleep time will help to enhance memory as well as the intellectual ability of the brain. That is why children often spend most of their time at this stage. 

3. The order and duration of a sleep cycle

A sleep cycle usually lasts from 90 to 110 minutes. The duration of deep sleep and intense deep sleep often last longer than that of dreaming stage in the early cycles. In contrast, near dawn, the time for deep and intense deep sleep gradually reduces and dreaming time lasts longer. 

4. How many sleep cycles do you need for a healthy body?

A typical night sleep needs about 5-6 full sleep cycles. There are no sleep cycles that are completely similar to the others. During the first 2-3 sleep cycles, we spend most of our time in non-rapid eye movement sleep (non-REM). During the next 2-3 sleep cycles, we spend most of our time in stage 1 (light sleep) and REM sleep. 

The body of each one has its own biological clock, and each individual has distinct sleep demand. In particular, there are many factors that impact sleeping hours, such as age, sport habits, stress, living conditions and pregnancy status. However, there are some certain factors that affect the necessary sleeping hours of an individual, and age is the strongest influencing factor. Here are the recommended sleeping hour from US National Sleep Foundation for each group of age:

Age group	Recommended hours of sleep
Infants under 2 months	14 – 17 hours
Infants from 2 months – 1 year old	14 – 17 hours
Toddlers (1 – 2 years old)	11 – 14 hours
Kindergarteners (2 – 5 years old)	10 – 13 hours
Teenagers ( 12 – 18 years old)	8 – 10 hours
Adults	7 – 9 hours
The elderly	7 -9 hours

FAQs about sleep cycles

When do we dream?

Dreams often appear during REM stage, the period when the brain is acting intensely, triggering dreams in the mind of sleepers and at the same time releasing some certain chemicals to prevent the body from reacting to dreams. During this stage, though the eyes are closed,the pupils of the eyes move quickly. Therefore, this stage is called Rapid Eye Movement. 

Why is the REM stage so important?

The REM stage contributes much more than the function of recovering the body. REM plays a pivotal role in subconsciously interpreting the events of the day so that people can learn new things. REM is closely related to the learning and memorizing ability of young children as well as adults. 

During the rapid eye movement (REM) stage of sleep, the brain sorts the information from the most important to the least important and transfers it to long-term memory. If this stage of the sleep cycle is altered, your concentration and acumen might decrease. Besides, you might feel irritable and short-tempered. 

Infants can spend up to half of their sleep cycle on REM, while adults only spend about 20% of a sleep cycle on this stage. When it comes to deep sleep, people under 30 years old spend 2 hours each night for this stage, while people over 65 years old only spend about 30 minutes with this slow wave stage. The EEG indicates that adults can actually spend most of their sleeping hours in light sleep, or in stage 2. 

Above is the information about the sleep cycle that we want to give you. Hopefully this post will help you to better understand sleep, thereby you can take better care of your sleep.

How to sleep better? Here’s a few tips for a better nights sleep

We naturlly feel tired twice a day: 2am and 2 pm. If you’re having a particularly bad night, try sleeping at your sleep cycle closest to 2am.

Exercising regularly makes it easier to fall asleep as well as having more sound sleep. Exercising right before bedtime often have the opposite affect.

The body never fully adjusts to shift work, those who work in off-hour shifts (early morning, night, or late afternoon jobs) report higher rate of insomia.

Avoid napping in the afternoon, this makes sleeping at nightly significantly more difficult and can disrupt your natural sleep cycle.