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😴 Sleep Calculator
Find your ideal bedtime or wake-up time using 90-minute sleep cycles.
Recommended Bedtime
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How Sleep Cycles Work
Your sleep isn't one continuous state — it moves through repeating 90-minute cycles of light sleep, deep sleep, and REM sleep. Waking up in the middle of a cycle (during deep sleep) leaves you groggy, even after a full night's rest. Waking up at the end of a cycle, when sleep is lightest, leaves you feeling refreshed.
This calculator works backward or forward from your target time in exact 90-minute blocks, so you wake up between cycles instead of in the middle of one.
Who Should Use This Calculator?
- Anyone who wants to wake up feeling refreshed, not groggy
- People setting an alarm and unsure what time to go to bed
- Shift workers adjusting their sleep schedule
- Parents planning bedtime routines around wake-up needs
A full sleep cycle — moving through light, deep, and REM sleep — takes approximately 90 minutes on average. Waking at the end of a cycle rather than in the middle of one reduces grogginess.
Sleep latency is the time it takes you to actually fall asleep after going to bed. The average is 10-20 minutes, which this calculator adds to your bedtime automatically.
Most adults need 5-6 cycles (7.5-9 hours) per night. Fewer than 4 cycles is generally considered insufficient for most adults.
No. All calculations happen instantly in your browser — nothing you enter is stored or shared.