Sleep Science Calculator
Wake up refreshed,
not groggy.
Most mornings feel rough because we wake up in the middle of a sleep cycle. Each cycle lasts about 90 minutes, so we help you pick a bedtime (or wake time) that lands gently between them, the way your body actually wants to wake up.
Target wake-up time
—
Falling asleep around —
Go to bed at
Based on 90-minute sleep cycles + ~15 min to fall asleep
Cycle-based
Based on the 90-minute REM/NREM rhythm studied in sleep research.
Wake up clearer
Rising between cycles avoids the heavy grogginess of deep-sleep wake-ups.
Private by design
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How it works
Your brain moves through sleep in cycles of roughly 90 minutes. Waking at the end of a cycle — when sleep is lightest — leaves you alert. Waking mid-cycle, especially during deep sleep, leaves you foggy. We add about 15 minutes for falling asleep, then count complete cycles backward from your wake time (or forward from your bedtime).
6
cycles · 9h
Optimal
5
cycles · 7.5h
Recommended
4
cycles · 6h
Minimum
3
cycles · 4.5h
Short rest