Sleep Requirements and Optimal Wake Times
Sleep is not one continuous state — it cycles through light sleep, deep sleep (slow-wave), and REM sleep in roughly 90-minute cycles. Waking mid-cycle causes grogginess (sleep inertia); waking at the end of a cycle feels natural and refreshed.
Recommended Sleep by Age (NSF / AAP)
- Newborns (0–3 months): 14–17 hours
- Infants (4–11 months): 12–15 hours
- Toddlers (1–2 years): 11–14 hours
- Pre-school (3–5): 10–13 hours
- School age (6–13): 9–11 hours
- Teenagers (14–17): 8–10 hours
- Young adults (18–25): 7–9 hours
- Adults (26–64): 7–9 hours
- Older adults (65+): 7–8 hours
Wake-Time Calculator (90-minute cycles)
Add ~15 minutes to fall asleep, then count forward in 90-minute increments:
Sleep at 22:30 → wake at:
00:00 (1 cycle) — too short
01:30 (2 cycles) — nap territory
03:00 (3 cycles) — short night
04:30 (4 cycles) — minimum viable
06:00 (5 cycles) — 7.5 hrs ✓
07:30 (6 cycles) — 9.0 hrs ✓Sleep Debt
Sleep debt accumulates when you consistently sleep less than your body needs. You cannot fully "repay" chronic sleep debt in one weekend — studies show cognitive performance stays impaired. The fix is consistent adequate sleep over 2–3 weeks.
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