Sleep Cycle Bedtime Calculator
Enter your wake-up time and get bedtimes that let you wake at the end of a 90-minute sleep cycle.
Wake between cycles, not mid-cycle
Feeling groggy after "enough" sleep often means the alarm went off in the middle of deep sleep. Sleep moves through roughly 90-minute cycles, so waking at the end of one feels far more refreshing. This tool counts whole cycles back from your target wake time to suggest when to go to bed.
It also adds the time it takes to actually drift off — about 15 minutes for most people — so the schedule reflects real sleep, not just time in bed. To wake at 7:00, for instance, good bedtimes land near 9:45, 11:15, or 12:45.
A guide, not a monitor
Cycle length varies from person to person, so treat these as strong suggestions. Everything is calculated in your browser and nothing you enter is uploaded.
Frequently Asked Questions
How does the bedtime calculator work?
Sleep runs in roughly 90-minute cycles. From your wake-up time it counts back complete cycles (plus about 15 minutes to fall asleep) so you aim to wake between cycles rather than mid-cycle.
Why 90 minutes?
A full sleep cycle averages about 90 minutes, though it ranges from 80 to 110. Waking at the end of a cycle, in lighter sleep, tends to feel less groggy than waking in deep sleep.
How many cycles do I need?
Most adults do well on five to six cycles (about 7.5–9 hours). The tool shows several bedtime options so you can pick one that fits your evening.
Is anything uploaded?
No. The times are calculated in your browser and nothing you enter is sent anywhere.
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