Sleep Time Calculator

Know the best possible times to wake up with this free app. The five stages of sleep, including their repetition, occur cyclically. The first cycle, which ends after the completion of the first REM stage, usually lasts for 90 minutes. With 8 hours of sleep you typically go through 4-5 cycles a night. Waking up in the middle of a cycle leaves you feeling groggy, but waking up at the end of a cycle leaves you feeling awake and alert. This app gives you recommendations on when to wake up in the morning to decrease the likelihood that you will feel groggy.