Schlafrechner

Enter the time you need to wake up. The calculator subtracts the selected number of estimated cycles and your fall-asleep buffer, then shows dated bedtime options.

Enter your bedtime, or select estimated sleep time if you already know when you usually fall asleep. The calculator adds the selected cycles to that instant.

No. Ninety minutes is a convenient planning estimate. NIH describes typical cycles as roughly 80–100 minutes, and cycle length varies between people and across a night.

Most adults need at least seven hours of sleep, which may be around five cycles at a 90-minute estimate. Total sleep duration matters more than mechanically matching a multiple.

Six hours is below the usual recommendation for most adults. A complete estimated cycle does not make a short night sufficient; consider the duration label and protect enough time for sleep.

The first-sleep-window card shows an approximate 90-minute window after estimated sleep onset. It is a planning reference, not a measurement of deep sleep or a guarantee of sleep quality.

No. A browser calculator cannot detect REM or non-REM sleep. Actual stages require professional sleep monitoring.

No. It does not diagnose insomnia, sleep apnea or any other condition. Seek professional advice for persistent insomnia, loud snoring, breathing pauses or daytime sleepiness.

No. Dates, times, age selection and time-zone calculations stay in your browser. Calendar files are generated locally and input values are not sent to analytics.