The human body cycles through 2 phases of sleep, rapid eye movement (REM) and nonrapid eye movement (NREM) sleep. The body cycles approximately 4 to 6 times each night, with each averaging 90 minutes. [1]

Waking up at the end of a cycle, when sleep is the lightest, often helps a person start the day feeling more well-rested.

Use this calculator to help choose a bed time or wake time.