Sleep Calculator
Find the best bedtime or wake time based on 90-minute sleep cycles — wake up feeling refreshed, not groggy.
Each sleep cycle lasts ~90 minutes. Waking at the end of a cycle prevents grogginess caused by interrupting deep sleep.
Wake-Up Goal
07:00
Includes ~15 min to fall asleep
5:15 PM
9 cycles · 13.5 hours of sleep
6:45 PM
8 cycles · 12 hours of sleep
8:15 PM
7 cycles · 10.5 hours of sleep
9:45 PM
6 cycles · 9 hours of sleep
11:15 PM
5 cycles · 7.5 hours of sleep
Sleep Science Notes
🔬 Adults need 7–9 hours (5–6 complete cycles) per night.
⚠️ Waking mid-cycle causes sleep inertia — grogginess that lasts for hours.
⏰ Times include ~15 min to fall asleep after lying down.
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