Sleep Cycle Calculator
Find the best time to wake up or go to bed based on 90-minute sleep cycles.
ℹ How it works
Sleep naturally progresses through ~90-minute cycles of light, deep, and REM sleep. Waking mid-cycle causes grogginess ("sleep inertia"), so the best alarm times align with cycle boundaries. This calculator adds 14 minutes for average sleep-onset latency and shows 4–6 wake-up options spanning 4.5–9 hours of sleep.
Recommended wake-up times
06:14
4 cycles
6h sleep
07:44
5 cycles
7.5h sleep
09:14
6 cycles
9h sleep
Includes 14 min to fall asleep
⚠️ This tool is for informational purposes only and does not replace medical advice. Consult a qualified doctor for health-related decisions.