A sleep cycle calculator is a tool designed to help optimize your sleep by aligning your wake-up time with your body's natural sleep cycles. It calculates the best times to wake up or fall asleep to ensure you wake up at the end of a sleep cycle, rather than in the middle, which helps you feel more refreshed and less groggy.

Key points about how a sleep cycle calculator works:
Sleep cycles last about 90 minutes: On average, a sleep cycle consists of light sleep, deep sleep, and REM (rapid eye movement) sleep, and it takes around 90 minutes to complete one full cycle.
Multiple cycles per night: Most people go through 4–6 sleep cycles each night.
Avoid waking up mid-cycle: Waking up in the middle of a deep sleep stage can leave you feeling tired and disoriented, even if you slept for a long time. The goal is to wake up at the end of a sleep cycle, when you're in a lighter stage of sleep, to feel more refreshed.

How it works:
Set wake-up time: You input the time you need to wake up, and the calculator suggests the ideal times to fall asleep based on completing full sleep cycles (usually in 90-minute increments).
Set sleep time: Alternatively, if you input when you plan to go to sleep, the calculator will provide the best times to wake up based on completing cycles.

For example, if you need to wake up at 7:00 AM, the calculator might suggest falling asleep at 10:00 PM, 11:30 PM, or 1:00 AM to optimize your wake-up time and help avoid sleep inertia. Would you like help calculating an optimal sleep or wake-up time based on this?