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Sleep calculator

When to go to bed or set the alarm so you wake between 90-minute sleep cycles.

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6 cycles · 9 hours 9:15 PM

How it works

bedtime = wake time − cycles × 90 min − time to fall asleep

Sleep runs in cycles of roughly 90 minutes, from light sleep to deep sleep and REM. Waking at the end of a cycle tends to feel easier than waking in deep sleep. Five or six cycles (7.5 or 9 hours) match the 7 or more hours adults are advised to get; four cycles (6 hours) is short. Cycle length varies from person to person, so treat these times as a starting point.

  1. Go to bed: wake time − cycles × 90 min − time to fall asleep 6:30 AM − 6 × 90 min − 15 min = 9:15 PM

Good to know

  • If you often feel unrested after enough sleep, or snore loudly, talk to a doctor; sleep apnea is common and treatable.

Printed from rocketcalc.io/health/sleep