Sleep Cycle calculator - Calculate Sleep Time

The sleep cycle can be defined as the oscillation between Rapid Eye Movement (REM) sleep and non-REM sleep, which will be discussed below. The timing of sleep largely relies on hormonal signals from the biological clock. The biological clock exhibits a regular rhythm that aligns with external cues (such as night/day) and can persist even if the external cues suddenly disappear. An example of this is jet lag, where the body's biological clock is affected due to rapid travel across long distances, resulting in the traveler feeling either delayed or ahead of their usual body time, which affects their sleep. Ideally, a person's sleep cycle follows their biological clock, but sleep can be influenced by various factors such as light, social timing (when others are awake, when work is required, etc.), napping, genetics, and more.

During sleep, the brain consumes much less energy compared to when a person is awake, especially during Rapid Eye Movement (REM) sleep. REM sleep is a type of sleep characterized by several aspects, including the eye movements it is named after, temporary body paralysis, and the occurrence of dreams. REM sleep and non-REM sleep are two distinct categories of sleep. Typically, the body cycles between non-REM sleep and REM sleep approximately every 90 minutes on average, occurring 4-6 times during a good night's sleep. Non-REM sleep begins and eventually transitions into slow-wave sleep, or deep sleep. During this period, body temperature and heart rate decrease, and the brain consumes much less energy while replenishing its supply of adenosine triphosphate (ATP), a molecule used for energy storage and transfer. Slow-wave sleep also involves the release of growth hormone, which is particularly important for human growth. REM sleep usually accounts for a smaller portion of total sleep time and is commonly associated with dreaming or nightmares. Deprivation of REM sleep can lead to anxiety, irritability, hallucinations, and difficulty concentrating. Studies have shown that when the body is deprived of REM sleep, subsequent sleep will include an increased number of attempts to enter REM sleep, as well as an increased amount of time spent in REM sleep compared to periods without sleep deprivation. This is referred to as REM rebound, which aligns with the belief that REM sleep is necessary for the body. The full understanding of REM sleep, its effects, and its necessity is still not completely comprehended. While it is considered an important and essential aspect of sleep, in some cases, temporary positive effects can be observed from REM sleep deprivation.

The quality of sleep can be measured by the level of difficulty a person faces in falling asleep and staying asleep, as well as the number of times they usually wake up during the night. It can also be measured subjectively by the person's level of comfort upon waking up. Poor sleep quality disrupts the sleep cycle and transitions between different sleep stages. To achieve good sleep quality, the need for sleep should be balanced with the daily sleep requirement. Ideally, the timing of sleep should be balanced so that the maximum concentration of melatonin hormone and the minimum core body temperature occur after the midpoint of the sleep period and before waking up.

Sleep is not a completely understood concept, and the amount of sleep a person needs can vary significantly based on specific factors such as age and individual differences. A person who gets sufficient sleep should not experience excessive sleepiness or functional impairment during the day. Generally, researchers have found that getting 6-7 hours of sleep per night is associated with several positive health outcomes, but there are also many other factors that can influence these results. As a person ages, their sleep tends to decrease, with newborns sleeping much longer hours than adults. This discrepancy diminishes with age, and sleep requirements become more similar to adult requirements starting around the age of five. The following are the recommendations from the Centers for Disease Control and Prevention (CDC) for the number of hours a person should sleep based on their age.