The Sleep Cycle Calculator helps you determine the most refreshing times to wake up or fall asleep based on natural 90-minute sleep cycles. By entering the time you plan to sleep or the time you need to wake up, the calculator estimates when you should wake up or go to bed to complete full cycles. Each cycle includes light, deep, and REM sleep stages, and waking at the end of a cycle helps you feel more alert and energetic. This tool is ideal for improving sleep quality, reducing morning grogginess, and maintaining a healthy sleep routine.