How the bedtime calculator works
How the candidates are computed
Sleep runs in repeating cycles of light → deep → REM. Waking at the cycle's end — in light sleep — feels dramatically better than waking mid-deep-sleep, which produces sleep inertia (that heavy, unwarranted grogginess lasting up to 30 minutes). The calculator starts from your wake time and steps backward in whole cycles, adding your fall-asleep latency. Each result is labeled with its total-sleep hours.
Choosing among the five
- 6 cycles (9 h) — the luxury option; rare on weekdays.
- 5 cycles (7.5 h) — the sweet spot for most adults; the default recommendation.
- 4 cycles (6 h) — workable occasionally; chronic 6-hour sleep builds measurable deficit (see the debt calculator).
- 3 cycles (4.5 h) — emergency only; impairment rivals alcohol.
The fall-asleep field matters
The listed bedtime is lights-out, not head-on-pillow. Most adults take 10–20 minutes to fall asleep; stressed nights take longer. If you regularly lie awake 45+ minutes, the honest fix is a later bedtime plus earlier light and caffeine cutoffs — not more time in bed rehearsing wakefulness.
Waking instead
Choose "sleep NOW" mode and the calculator projects wake times that land on cycle boundaries — useful for naps and for those nights when the schedule collapses. Same math, forward.