Sleep Cycle Calculator
Find your ideal bedtime or wake time based on 90-minute sleep cycles.
Includes ~15 min to fall asleep. Best options are highlighted.
Sleep at 9:45 PMRecommended
6 cycles · 9 hours of sleep
Sleep: 9:45 PM
Wake: 7:00 AM
Sleep at 11:15 PMRecommended
5 cycles · 7.5 hours of sleep
Sleep: 11:15 PM
Wake: 7:00 AM
Sleep at 12:45 AM
4 cycles · 6 hours of sleep
Sleep: 12:45 AM
Wake: 7:00 AM
Sleep at 2:15 AM
3 cycles · 4.5 hours of sleep
Sleep: 2:15 AM
Wake: 7:00 AM
Sleep at 3:45 AM
2 cycles · 3 hours of sleep
Sleep: 3:45 AM
Wake: 7:00 AM
How sleep cycles work
A sleep cycle lasts approximately 90 minutes and progresses through light sleep, deep sleep, and REM sleep. Waking up between cycles (rather than mid-cycle) reduces sleep inertia — that groggy feeling. Most adults need 5–6 cycles (7.5–9 hours). This calculator adds 15 minutes for the average time to fall asleep and shows options from 6 cycles down to 2. Related: time duration calculator.
Private & free — this tool runs entirely in your browser.
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