Sleep Cycle Calculator

Wake up refreshed by timing your sleep to natural 90-minute REM cycles.

Target Wake-Up Time

Includes ~15 min fall-asleep buffer. Bedtimes shown below.

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❓ How Does This Work?

Sleep cycles last approximately 90 minutes, each ending with a period of lighter sleep — the ideal moment to wake up. Most adults need 5–6 complete cycles (7.5–9 hours).

This calculator adds a 15-minute fall-asleep buffer and then counts backward (or forward) in 90-minute increments to give you the perfect bedtime or alarm time.

Waking at the end of a cycle instead of the middle dramatically reduces sleep inertia — the grogginess that hits when your alarm catches you in deep sleep.