The online calculator will help you calculate the time to Wake up.
A great option for each person to know the best time to Wake up.
The sleep of a healthy person consists of two phases, REM sleep (~20 minutes) and slow wave sleep (~2 hours).
These phases of sleep constantly, alternating.
During slow sleep the human body is restored, and during a quick rest and test the internal systems.
In a fast sleep, a person can toss and turn or even to mutter something, since the brain is in an active state.
Waking up at this time the most easy and helpful for the body.