About this tool
This calculator is for anyone who wants to wake up at the end of a sleep cycle rather than in the middle of one, which is widely believed to make waking up feel easier. It works backward or forward from your target time in 90-minute blocks, the average length of one full sleep cycle, plus about 15 minutes to actually fall asleep.
How to use it
- Choose whether you want to set a wake-up time or fall asleep right now.
- If setting a wake-up time, enter it.
- Review the suggested times, each a whole number of 90-minute sleep cycles apart.
Frequently asked questions
Why 90 minutes?
A full sleep cycle — moving through light sleep, deep sleep and REM sleep — lasts roughly 90 minutes on average for most adults, though it varies a bit from person to person.
Why does it add 15 minutes?
That accounts for the average time it takes to actually fall asleep after getting into bed, so the sleep cycles start from a realistic point rather than the exact moment you lie down.
Is this based on real sleep science?
It's based on the well-documented concept of 90-minute sleep cycles, but everyone's cycles vary somewhat in length, so treat the suggested times as a helpful guide rather than an exact science.