Calculate the best times to sleep and wake up for full sleep cycles.
A Sleep Calculator helps you wake up feeling refreshed by timing your sleep with natural 90-minute sleep cycles.
Sleep Time = Wake Time − (N × 90m) − 15mWaking up in the middle of a deep sleep cycle is why you often feel groggy even after 8 hours of sleep. Our tool uses the science of "Sleep Cycles" to help you time your alarm perfectly.
Human sleep happens in stages, usually lasting about 90 minutes. By waking up at the end of a cycle, you are in "light sleep" and feel much more alert. Most adults need 5 or 6 cycles (7.5 or 9 hours) to fully recover.
Wake up at 7:00 AM -> Go to sleep at 9:45 PM or 11:15 PM