Wake up between cycles, not mid-deep-sleep. Tell it when you need to wake up and it finds the bedtimes that fit whole 90-minute sleep cycles.
Go to bed at one of these times:
If you fall asleep around , set your alarm for:
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Each ~90-minute cycle ends in light sleep — the natural exit point. An alarm mid-deep-sleep is what causes that crushed-by-a-truck feeling.
7.5–9 hours of actual sleep suits most adults. Consistency matters more than perfection — same time daily beats heroic weekends.
Pair a fixed bedtime with white noise and a dim screen — your falling-asleep buffer will shrink on its own.
No — real cycles run roughly 80–110 minutes and lengthen through the night. 90 is the practical average; treat the suggested times as targets, not prescriptions.
Pick the closest one and keep it consistent. A regular "good enough" schedule beats an optimal one you can't keep.
Short naps (20 min) avoid deep sleep entirely; full-cycle naps (90 min) wake you at a cycle boundary. The in-between zone (45–60 min) is where nap grogginess lives.