Sleep Cycle Calculator
Calculate the optimal time to go to bed to ensure you wake up between sleep cycles feeling refreshed.
The Science of Sleep Cycles
Human sleep is not uniform. Throughout the night, your brain cycles through different stages of sleep, moving from light sleep to deep sleep, into REM (dream) sleep, and back again. One complete cycle lasts approximately 90 minutes.
Why Cycles Matter
If your alarm wakes you up in the middle of a deep sleep stage, you will experience "sleep inertia"—that heavy, groggy feeling that takes hours to shake off. If you wake up at the end of a cycle, you will feel naturally alert and refreshed, even if you slept fewer total hours.
How We Calculate
This calculator works backward from your desired wake-up time in 90-minute increments. It also adds an average of 15 minutes to account for the time it takes the average human to fall asleep once in bed.
Frequently Asked Questions
How many cycles do I need?
Most adults feel their best after completing 5 cycles (7.5 hours) or 6 cycles (9 hours) per night.