Sleep Calculator
Calculate the ideal bedtime or wake-up time based on natural 90-minute sleep cycles, so you wake up feeling rested.
Recommended bedtimes
12:45 PM
6 cycles · 9h
2:15 PM
5 cycles · 7h 30m
3:45 PM
4 cycles · 6h
5:15 PM
3 cycles · 4h 30m
Sleep happens in ~90-minute cycles, and waking up at the end of a cycle (rather than in the middle of one) generally feels more refreshing. We've added a 15-minute buffer to fall asleep.
How the Sleep Calculator works
Choose whether you have a fixed wake-up time or a bedtime in mind, then enter that time. The calculator works backward or forward in 90-minute sleep cycles — the average length of one full sleep cycle — to suggest several bedtimes or wake-up times that align with the end of a cycle, which can make waking up feel easier.
Frequently asked questions
Why does sleep work in 90-minute cycles?
A full sleep cycle — moving through light sleep, deep sleep, and REM sleep — takes roughly 90 minutes on average. Waking up at the end of a cycle tends to feel easier than waking mid-cycle.
How many cycles should I aim for?
Most adults feel best with 5–6 cycles (about 7.5–9 hours) of sleep per night, though individual needs vary.
Why is there a 15-minute buffer added?
It typically takes the average person about 15 minutes to fall asleep after getting into bed, so that time is added when calculating a recommended bedtime.