Plan a bedtime or wake-time window using variable cycle lengths.
Preparing calculator…
Cycles are not fixed at 90 minutes and vary between people and nights. The tool shows a window, not a medical conclusion.
Not a diagnosisFor general health education and estimation only. It does not diagnose a condition and is not treatment, medication, diet or training advice.
time window = target time ± cycles × 80–100 minutesAdults planning a bedtime or wake-time window.
Not a diagnostic tool for insomnia, sleep apnoea or another sleep disorder. Shift work, age and illness alter sleep structure.
Input accuracy, measurement technique, rounding and individual variation all affect the result. Internal precision is retained and only displayed values are rounded.
Seek medical advice when insomnia, daytime sleepiness, choking or persistent sleep problems affect daily life.