Bedtime Calculator (90-Min Cycles)
Reverse engineer your ideal bedtime to avoid waking up during deep sleep.
Recommended Bedtimes:
*Times include an assumed 15 minutes to fall asleep (sleep latency).
Methodology & Assumptions
Sleep Architecture
Human sleep occurs in cycles of approximately 90 minutes, progressing from light NREM, into deep NREM, and finally into REM sleep. Waking up in the middle of deep NREM (stage 3/4) causes severe sleep inertia (grogginess). Waking up at the end of a cycle (after REM) ensures a rapid transition to alertness.