The amount of time you need for sleep will change by your age. An infant may need up to 17 hours of sleep each day, while an adult may just need 7 hours of sleep a night.

Your brain and body will go through a different cycle of sleep when you fall asleep, and each cycle includes five distinct stages. 

• First Stage: this is the first stage of sleep between being awake and falling asleep
• Second Stage: you become unaware of the surrounding environment, and your body temperature will drop gradually
• Third & Fourth Stage: you will reach deep sleep at this stage, and your breathing and heart rate will reach their lowest levels
• REM (rapid eye movement) sleep: as the final stage of your sleep cycle, your brain becomes most active and dream occurs. It will boost both your physical and mental performance when you wake up

Adults need to complete at least 5 or 6 sleep cycles per night. On average, you may need 10-20 minutes to fall asleep, and it takes about 90 minutes to go through each sleep cycle. 
Five cycles are about 7.5 hours of sleep a night, while six full cycles are about 9 hours of sleep. Ideally, you usually feel more refreshed when you wake up at the end of a sleep cycle.

Sleeping time are based on your wake-up time, five or six complete sleep cycles and 15 minutes to fall asleep.