Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
Sleep runs in ~90-minute cycles; waking between cycles feels easier. Includes ~15 minutes to fall asleep.
DISCLAIMER: Cycle lengths vary from person to person; treat these as starting points. Adults generally need 7–9 hours. Not medical advice.
What Is the Sleep Calculator?
The Sleep Calculator works backwards (or forwards) in 90-minute sleep cycles — plus about 15 minutes to fall asleep — to suggest bedtimes or wake-up times that land between cycles, when waking feels easiest.
How It Works
Pick whether you know your wake-up time or your bedtime, set the time, and see four suggestions ranked by cycles of sleep.
When to Use It
Use it before an early alarm, a flight or an exam to wake up feeling refreshed instead of groggy.
Frequently Asked Questions
- Why 90 minutes?
- A full sleep cycle (light → deep → REM) averages about 90 minutes. Waking at the end of a cycle, rather than mid-deep-sleep, usually feels much better.
Last reviewed: 2026-06-27