Sleep Cycle Calculator

Wake up at the end of a 90-minute sleep cycle instead of in the middle of one. Pick a mode below — no account, no uploads, just math.

What time do you need to wake up?

Tap the button when you're about to close your eyes. We'll add ~14 minutes to fall asleep, then count full sleep cycles.

A 20-minute nap boosts alertness without grogginess. A 90-minute nap completes one full cycle.

How it works

Choose a mode: wake-up time, "sleep now", or a power nap.
We count backwards (or forwards) in 90-minute sleep cycles and add about 14 minutes to fall asleep.
Pick a time, set your alarm, and wake up at the light end of a cycle.

FAQ

Why 90 minutes?

A full sleep cycle — light sleep, deep sleep and REM — lasts about 90 minutes for most adults. Waking at the end of a cycle feels much easier than waking in the middle of deep sleep.

How many cycles do I need?

Most adults feel best with 5–6 full cycles (7.5–9 hours of sleep). This calculator shows options for 4, 5 and 6 cycles so you can pick what fits your schedule.

Is a 20-minute nap really better than an hour?

Often, yes. A 20-minute nap stays in light sleep so you wake up alert. An hour-long nap drops you into deep sleep and you wake up groggy — that's called sleep inertia.

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