Sleep Cycle Calculator
Waking at the end of a 90-min cycle feels best. Enter your wake time to get 4 recommended bedtimes.
Why cycles matter
Sleep runs in 90-min cycles (light → deep → REM). Waking mid-cycle triggers sleep inertia (grogginess) for 30+ min. Waking at cycle end (just after REM) feels instantly fresh. Adult recommendation: 4–6 cycles (6–9 hours).