Sleep Cycle Calculator — 90-Minute REM Cycles, Optimal Bedtime &
Calculate your optimal bedtime or wake-up time using 90-minute sleep cycles and sleep onset latency. Free, instant, and accurate.
Sleep Cycle Calculator
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Optimal Times
[{"time":"9:16 PM","cycles":6,"hours":9},{"time":"10:46 PM","cycles":5,"hours":7.5},{"time":"12:16 AM","cycles":4,"hours":6},{"time":"1:46 AM","cycles":3,"hours":4.5}]
Sleep Cycles
6 complete cycles (9.0 hours)
Scenario Comparison
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Go to bed at
9:16 PM
6 complete cycles (9.0 hours)
9:16 PM
6 cycles · 9.0 hours
10:46 PM
5 cycles · 7.5 hours
12:16 AM
4 cycles · 6.0 hours
1:46 AM
3 cycles · 4.5 hours
Each sleep cycle is ~90 minutes
A complete sleep cycle includes light sleep (N1), stable sleep (N2), deep sleep (N3), and REM sleep (when dreaming occurs). Waking at the end of a cycle leaves you feeling refreshed. Waking mid-cycle can cause grogginess and brain fog.
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