Sleep Cycle Calculator: Wake Up Refreshed, Not Tired
Use science to find your perfect bedtime. Align with your 90-minute sleep cycles to wake up at the optimal time and avoid morning grogginess.
Sleep Cycle Calculator
What is a Sleep Cycle?
A full sleep cycle lasts roughly 90 minutes. During this time, your brain moves from light sleep to deep sleep, and finally to REM (Rapid Eye Movement) sleep. Waking up during deep sleep causes "sleep inertia," leaving you tired for hours.
How Accuracy Works
This tool calculates your cycles by adding a 14-minute average for falling asleep. By timing your alarm to go off at the end of a REM cycle, you wake up naturally as your brain is already transitioning back to alertness.
How Many Cycles Do You Need?
While sleep needs vary, most adults thrive on 5 or 6 full cycles (7.5 to 9 hours). However, 4 cycles (6 hours) is often better than 4.5 cycles (6.75 hours) because you wake up at the end of a cycle rather than in the middle of deep sleep.
Optimizing Your Rest by Age
Individual requirements may vary based on health and lifestyle factors.
Napping During the Day?
If you can't get 5 full cycles at night, a tactical nap can help. Use our specialized tool to time it perfectly.
Try the Nap CalculatorFrequently Asked Questions
Why do I feel tired after 8 hours of sleep?⌄
Total hours matter less than sleep timing. If your alarm goes off while you are in "Deep Sleep" (Stage 3), you will experience sleep inertia. It is often better to sleep for 7.5 hours (5 cycles) than 8 hours (waking up mid-cycle).
How long does it take to fall asleep?⌄
On average, a healthy adult takes 14 minutes to enter the first stage of sleep. Our calculator automatically accounts for this time when suggesting your best bedtime.
Can I use this for my child?⌄
Children have different sleep cycle lengths and requirements. For specific age-based needs, we recommend using our Sleep by Age Calculator.