What is a sleep cycle?
When you fall asleep, your body moves through light sleep (stages 1β2), deep sleep (stage 3), and REM sleep (a lighter stage where dreaming occurs), completing one sleep cycle roughly every 90 minutes. Waking up right at the end of a full cycle β during light sleep β is said to feel much more refreshing than waking up in the middle of deep sleep.
How is this calculated?
Starting from your desired wake-up time, this calculator counts backward in 90-minute sleep cycles (3 to 6 cycles, or 4.5 to 9 hours total) and subtracts your typical time to fall asleep (about 14 minutes on average) to suggest several recommended bedtimes. Enter a bedtime instead, and it works the same way in reverse to suggest wake-up times.
A note on accuracy
Both the length of a sleep cycle (about 90 minutes on average) and the time it takes to fall asleep are general averages that vary from person to person. Use this calculator as a reference β the most accurate way to find your own ideal sleep pattern is to track how you feel after waking up over several days. If you have chronic sleep deprivation or insomnia, please consult a doctor.
Frequently Asked Questions
Why does it suggest several different times?
Recommended sleep duration for adults typically falls between 6 and 9 hours (4 to 6 sleep cycles), so this calculator shows several options within that range. Pick whichever fits your schedule for the next day.
Is it bad to sleep for shorter or longer than 90-minute cycles?
90 minutes is just an average, not an absolute rule. An individual's actual sleep cycle can range anywhere from 70 to 120 minutes, so the recommended times here may not be exactly right for you. The best approach is to track how you feel over several days of waking up and find the pattern that works for you.