Sleep
Sleep Cycle Calculator
Every 90 minutes, your brain completes one full sleep cycle. Waking mid-cycle leaves you groggy. This calculator finds the windows where waking up is actually easy.
Calculator
Find Your Sleep Windows
:
Go to bed at...
4 cycles · 6h
12:46 AM
5 cycles · 7h 30mOptimal
11:16 PM
6 cycles · 9hOptimal
9:46 PM
Includes 14 minutes to fall asleep — the average for healthy adults. Waking between cycles leaves you feeling groggy; waking at the end of a cycle is when you're in lightest sleep.
Why 90 minutes?
- 🌀Sleep cycles: Each cycle moves through light sleep, deep sleep, and REM. A full cycle takes roughly 90 minutes.
- ⏰Complete cycles matter: Waking mid-cycle, especially during deep sleep, triggers sleep inertia — the groggy, disoriented feeling that takes 20–30 minutes to clear.
- 💤5–6 cycles is the sweet spot: That's 7.5–9 hours. Fewer than 4 cycles (6 hours) leaves meaningful recovery debt over time.
Go deeper with the Sleep Protocol
The complete framework for sleep quality, timing, and recovery.
