Bedtime Calculator

What it does

Tell it when you need to get up and it suggests bedtimes. Each suggestion allows about 15 minutes to fall asleep, then whole 90-minute sleep cycles, so you are more likely to wake at the end of a cycle rather than the middle of one.

How sleep cycles work

While you sleep, your body moves through lighter and deeper stages and back again. One trip through takes roughly 90 minutes. Waking up in the middle of a deep stage often feels groggy, while waking between cycles can feel easier. Most adults do well on 5 cycles (7.5 hours), but people differ.

This is a general guide, not medical advice. If you often feel very tired or struggle with sleep, talk to your doctor.