A Sleep Cycle Calculator is a simple tool that helps you plan your sleep so you wake up at the end of a full sleep cycle, not in the middle of deep sleep. This makes it easier to feel refreshed, alert, and ready for the day, rather than waking up groggy or disoriented.

Each sleep cycle lasts around 90 minutes and includes different stages: light sleep, deep sleep, and REM (rapid eye movement) sleep. The calculator works by recommending ideal bedtimes or wake-up times based on 4 to 6 full cycles—typically 6 to 9 hours of sleep—so you can sync with your body’s natural rhythm.

This tool is especially useful for people who struggle with waking up tired, even after a full night’s rest. It doesn’t replace good sleep habits, but it complements them by helping you make smarter decisions about when to sleep or set your alarm.