Sleep Calculator
Wake at the end of a 90-minute sleep cycle to feel less groggy.
Result
6 cycles (9h)Bedtime 21:45
5 cycles (7.5h)Bedtime 23:15
4 cycles (6h)Bedtime 0:45
Sleep Calculator — FAQs
What are sleep cycles?
Sleep moves through ~90-minute cycles of light, deep and REM sleep. Waking mid-cycle (especially in deep sleep) causes grogginess; waking at cycle end feels easier. The calculator adds ~15 min to fall asleep.
How much sleep do I need?
7–9 hours for adults. Sleep cycles run ~90 minutes — waking mid-cycle feels groggy, so time wake-ups to cycle ends.
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