Sleep Cycle and Stages

Sleep Cycle

During the night, sleeping follows a predictable pattern, moving back and forth between deep sleep and REM sleep. Together, REM and non-REM sleep stages form a complete sleep cycle. Each cycle typically lasts about 90 minutes and repeats four to six times over the course of a night.

Non-REM sleep

First stage also known as "transitional sleep" – it lasts for about five minutes. Your eyes move slowly under the eyelids, muscle activity slows down, and you are easily awakened.

Second stage also known as "light sleep" – This is the first stage of true sleep, lasting from 10 to 25 minutes. Your eye movement stops, heart rate slows, and body temperature decreases.

Third stage also known as "deep sleep" – in this stage it's difficult to awaken, and if you forcibly wake up, you do not adjust immediately and often feel groggy and disoriented for several minutes. In this deepest stage of sleep, your brain waves are extremely slow. Blood flow is directed away from your brain and towards your muscles, restoring physical energy.

REM sleep

REM sleep (this is where dreams occur) – time to get there is approximately 70 to 90 minutes after falling asleep. Your eyes move rapidly, your breathing shallows, and your heart rate and blood pressure increase. During this stage, your arm and leg muscles are paralyzed.

Our sleep cycle calculator considers sleep cycle durations, REM and Non-REM sleep patterns to accurately determine what time should you wake up at to feel rested and less groggy and mostly to avoid waking up in the middle of a sleep cycle.